# Heating RO water



## SlipperFan (Sep 17, 2009)

Here's the situation:

We are planning to build a "conservatory" (for orchid growing now, and later for anything whoever has this house after us). We've looked into using our well water -- too high in calcium and iron, bringing in water from our pond -- too expensive, and now we are thinking about an RO system. Likely this system would be in our basement with a hookup to the conservatory. In our basement, the water would be too cool to use directly.

So we need to heat it some way. But our heating/plumbing guy says he cannot find an appropriate heater because of the caustic nature of pure water.

How has anyone else solved this problem?


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## goldenrose (Sep 17, 2009)

Could a barrel or some type of storage device be in the conservatory? It could be refilled daily, if needed, right after watering & the water should be up to room temp by the next day when you're needing/using it.


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## SlipperFan (Sep 17, 2009)

That's the only think I could think of, Rose. But storage would take up precious space in the conservatory, space I'd rather use for orchids.


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## goldenrose (Sep 17, 2009)

I hear you Dot but without the water quality, you know what will happen to the orchids.
How about the rubbermaid storage that fits under beds? Low & flat, under the bench wouldn't be taking up usable space.


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## SlipperFan (Sep 17, 2009)

I won't be having traditional benches. I'll be using step benches and stands. There won't be room under these.


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## Clark (Sep 17, 2009)

I'm soooooo jealous, good luck with this project!


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## NYEric (Sep 17, 2009)

What would be the temp increase you want from a cellar storage tank to dispensing? In High School my Sr. project was a solar heating system, hint, hint..


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## goldenrose (Sep 17, 2009)

SlipperFan said:


> I won't be having traditional benches. I'll be using step benches and stands. There won't be room under these.


Gosh darn you're making it difficult! :wink:
I think Eric needs to explain more about his solar heating idea(s)!


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## gonewild (Sep 17, 2009)

How much water do you need to heat?
Think about using an aquarium heater.


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## tim (Sep 17, 2009)

they make electric aquarium heaters that screw into a pvc line - google "fireplug aquarium heater"


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## suss16 (Sep 17, 2009)

I use a 200 watt aquarium heater in my 32 gal resevoir... no problems last winter. I set it to 72.


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## Leo Schordje (Sep 17, 2009)

Another alternative is to plumb the feed line for your RO system to either the hot water system or to a mixer valve, and pull in both hot water and cold water. I am not sure the operating temp range for the RO membrane but I think they work best with water in the 50 to 90 F range. I don't use an RO system, but my water tank has both hot and cold feed so in summer I can use just cold water, in winter I can use a mix.


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## SlipperFan (Sep 17, 2009)

Eric, I live in Michigan -- solar heating would be iffy with all our cloudy days, especially in the Winter. 

Lance, I've looked into an aquarium heater option, but I've not been able to find out anything about using it to heat RO water. 

Leo -- I'm not understanding your solution. Our hot water heater is softened water, so that won't work for watering orchids. Our water right out of the ground is very high in hardness and leaves all kinds of water spots all over the leaves, although it doesn't seem to be harmful to the plants. I'd like to avoid the spotting if possible. Our plumbing guy says he can't find a heater for RO water because of it's corrosiveness.

Here's a quote from our Heating/Plumbing guy: "I have not found a water heater that is designed to work with the RO water due to its corrosiveness."

tim, I did a little searching, but found that the company that made the "Aquanetics Fireplug Heater Module" is out of business. Do you have any specific leads?


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## gonewild (Sep 17, 2009)

RO water won't hurt an aquarium heater.
Salt water aquariums?

They are made of plastic and glass and are sealed so they can be submerged.
I have had one soaking in RO water for 2 years and it still works fine.
Low cost for an easy solution.

I think your plumber is looking at conventional H2O heaters which have pipes attached.


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## Candace (Sep 17, 2009)

Dot, it sounds like an electric aquarium heater would be your best option. Unless your basement gets really cold... Yes, the pipes leading into a conventional heater would corrode over time from the R.O. It's nice your plumber knows this. I bet others would just set it up and let you deal with the problems later!

I think most people keep their storage tanks in their g.h.s. My tanks are all under my benches. So, I don't really have to worry about the water temp. But, I used to have several salt water aquariums and the heaters worked great.


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## phrag guy (Sep 17, 2009)

I use an aquarium heater for years in my R.O. water in the basement


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## cnycharles (Sep 17, 2009)

if you didn't want to go the aquarium heater route, you could set up a tank that has standard hot water in it, then run a long plastic tube from your r/o setup through this tank. this is how you can run a 'warm water' heating system in a house/greenhouse etc. It's called a heat exchanger. Your standard hot water heater unit/tank won't ever be exposed to pure water. you might be able to retrofit your existing hot water tank so that you can run a bunch of the tubing in around inside and out of the reservoir. enough plastic tubing and you'll easily be able to warm up the pure water as long as it isn't rushing through, or just used slowly


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## SlipperFan (Sep 17, 2009)

cnycharles said:


> if you didn't want to go the aquarium heater route, you could set up a tank that has standard hot water in it, then run a long plastic tube from your r/o setup through this tank. this is how you can run a 'warm water' heating system in a house/greenhouse etc. It's called a heat exchanger. Your standard hot water heater unit/tank won't ever be exposed to pure water. you might be able to retrofit your existing hot water tank so that you can run a bunch of the tubing in around inside and out of the reservoir. enough plastic tubing and you'll easily be able to warm up the pure water as long as it isn't rushing through, or just used slowly



Maybe that's what Leo was talking about?

I don't know if it's feasible to use our current hot water heater -- it's pretty old. But I'll run the idea by our plumber. As well as the Aquarium heater idea.

Thanks, everyone!


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## cnycharles (Sep 17, 2009)

you wouldn't be able to modify a 'glass-lined' heater by putting holes in it, but a plain tank you would be able to plumb in fittings. you could have a tank after your hot water heater that could have water running through it constantly (between heater tank and next tank), and have the tubing in the second tank


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## SlipperKing (Sep 18, 2009)

I'm not sure I follow others concerns here over water temperature in the winter months. Granted, if you're using ground water and it's freezing or below outside you would need to take the "chill" out of the water. We're talking about RO water stored in a tank, in a basement not in an ice rink. Are you northern folks saying it's freezing or below in your basements? I don't think so. A simple aquarium heater, 40 bucks will take the chill out of 55gal of water in a 24 hr period. You may not what to wash your face or take a bath in it but it will perfectly fine for your plants. 
The last time I checked when it's winter in S.E. Asia, it's WINTER TIME, cold air, cold rains. Lets mimic nature, 50 degree air temp then 50 degree or abouts water.


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## NYEric (Sep 18, 2009)

Haven't you heard that in the MidW they play ice hockey in their basements?!


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## Leo Schordje (Sep 18, 2009)

SlipperFan said:


> Maybe that's what Leo was talking about? Thanks, everyone!



Actually Dot, you answered the question about why my method would not work. Your hot water heater is heating softened water, which you can't use due to the extra salt. So I would recomend some sort of holding tank were you could put in an aquarium heater. IF the holding tank is over 100 gallons, consider a livestock water trough heater. 

Leo


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## likespaphs (Sep 18, 2009)

this may have been mentioned but what about using the r.o. filter either after the heater or putting a holding tank in the conservatory. the area would probably be warm enough for the water to be used directly. the only problem could be hiding the tank, so to speak


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## SlipperFan (Sep 18, 2009)

likespaphs said:


> this may have been mentioned but what about using the r.o. filter either after the heater or putting a holding tank in the conservatory. the area would probably be warm enough for the water to be used directly. the only problem could be hiding the tank, so to speak



We may have to put the whole system in the conservatory, but as I mentioned, I'd rather not have to use the space there.

Thanks for the tips, everyone. Now I'd really like to find someone locally who understands this system and knows how to set one up for my needs.


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## cnycharles (Sep 19, 2009)

mimicking temperatures like having 50 degree air and water temperature is great if that's the normal temp for the plants. if it's phal or anything remotely like it that never gets temps below 66 degrees, then it could be very bad. cold water on warm plants or cold water on a plant that is dangerously close to it's minimum tolerable temperature could cause physical damage to leaves or worse


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## gonewild (Sep 19, 2009)

cnycharles said:


> mimicking temperatures like having 50 degree air and water temperature is great if that's the normal temp for the plants. if it's phal or anything remotely like it that never gets temps below 66 degrees, then it could be very bad. cold water on warm plants or cold water on a plant that is dangerously close to it's minimum tolerable temperature could cause physical damage to leaves or worse



You are exactly right. The significant point is the temperature difference between the leaf tissue and water temperature. 

If you think about it when rain falls it feels cold to us and it may in fact be actually colder than the air temperature. But when it finally hits a plants leaf it is likely very close to the leaf tissue temperature because the leaf has been cooled to less than air temperature by evaporative cooling.

By far the best location for the water supply tank is in your conservatory. If you locate it inside you don't need to worry about heating the water. The water in the holding tank will be the same temperature as the surrounding environment. Also you will have the advantage of the water tank acting as a heat sink. It will absorb daytime heat and store it for release at night when the air temperatures drop.


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## John M (Sep 19, 2009)

I store my R.O. water in an underground, 6,000 gallon concrete cistern next to the greenhouse. The water temperature hovers around 50*F year round. That's too cold. So, I rent a 60 gallon electric water heater from Ontario Hydro for ~$12 per month. When it breaks down, they repair/replace it!

BTW, Dot. What are you using as your feed water that goes *to* the R.O....presoftened water or raw well water?


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## SlipperFan (Sep 19, 2009)

John M said:


> I store my R.O. water in an underground, 6,000 gallon concrete cistern next to the greenhouse. The water temperature hovers around 50*F year round. That's too cold. So, I rent a 60 gallon electric water heater from Ontario Hydro for ~$12 per month. When it breaks down, they repair/replace it!
> 
> BTW, Dot. What are you using as your feed water that goes *to* the R.O....presoftened water or raw well water?



The plan is to use the softened water. The raw well water is too hard.


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## John M (Sep 20, 2009)

SlipperFan said:


> The plan is to use the softened water. The raw well water is too hard.




That's what I thought you'd say. It seems sensible to pre-treat the water (soften it), to extend the life of the R.O. membrane. After all, the R.O. will remove the sodium; but, 
*NO, NO, NO!!!! Don't do that!!!*

You'll kill all your plants. I know. I've been there and done that and killed my plants. I used to grow in my basement and I used pre-treated (softened), water as feed water to the R.O. However, I stored the product water in a bunch of Rubbermaid 17 gallon garbage pails. When each pail was full of R.O., I'd remove about 10% of it and replace it with some raw well water, which was super hard. However, the resulting mixture was still quite soft and my orchids loved it. 

*THEN*, I got the bright idea to begin using a complete hydroponic fertilizer. Now I didn't have to go to the bother of manually removing a couple gallons of R.O. water and replacing it with raw well water, because the fertilizer would provide all the calcium and other minerals needed. Well, that may be true; but, the pure R.O. water that I used inbetween feedings poisoned my plants and killed them. 

The reason is because the R.O. only removed a percentage of the disolved solids. Some elements are 99% removed and others are only 95%, or 88%, etc., removed. The result is nearly pure water; but, not 100% pure. Since your softener will put in a ton of sodium to replace the calcium that it removed, your feed water will be very high sodium. After it goes through the R.O., the levels of of other minerals in the product water will be so close to 0, they may as well be 0. However, because the sodium in the pre-treated (softened), water started out so very, very high, even after 90-some-odd percent is removed, you'll still have some left. That is VERY important to keep in mind. Even though the ppm of sodium will be very low, far less than 50, which is fairly acceptable for watering most plants, it will be the ONLY thing in the water. Therefore, what happens is that the plants get a steady diet of very low sodium...only sodium. There is no other minerals for them to take up, just sodium and they do it very efficiently. After a while, with no competition for the plant's attention from other minerals, the sodium levels in the plant tissues reaches toxic levels and you start to see plants die. They look like they're dehydrated; but, they've got live roots and you're watering them; but, they still don't seem to be taking up any water. Eventually, they just die. 

If you use feed water that has been pre-treated (softened), you *MUST* replace about 10% with some of your raw well water. Because there will then be a buffet of other helpful minerals; but, still in very low concentration, your plants won't overdose on sodium. They will take up less sodium because they are also busy taking up other elements.

Now, all that being said, I currently water my greenhouse with pure R.O. water. I do not add any raw well water back into the R.O. product water. *However, the feed water that I use is raw well water, not pre-treated (softened), water.* My raw well water is really hard (about 800 ppm TDS). Still, the R.O. membranes (three - 75 gpd) last about a year. I keep a close eye on their production. Whenever they're slowing down, I just pour a cup or two of Muriatic Acid (Hydrochloric Acid) into the sediment pre-filter and run that through the membranes. Works like a charm at disolving the calcium and restores the membranes to a reasonable production level. Of course, I keep an eye on the quality of the product water and it stays at a TDS ppm of 0 - 10....very pure.....and *NO* sodium poisoning problems.

Good luck!


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## SlipperFan (Sep 20, 2009)

Well, you certainly got my attention, John! I will have to run this by my water guy. Is it possible that some RO systems filter out more sodium than others? What's this about 3-phase & 4-phase systems?


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## John M (Sep 21, 2009)

SlipperFan said:


> Well, you certainly got my attention, John! I will have to run this by my water guy. Is it possible that some RO systems filter out more sodium than others? What's this about 3-phase & 4-phase systems?



I think that a 3-phase and/or a 4-phase system refers to the number of filters in total, including the R.O. membrane. My system is 2-phase. Each R.O. membrane has one sediment filter ahead of it....total. That equals two types of filter that the water passes through. Others also have a carbon filter, either before or after the R.O. membrane. That would be a 3-phase. I guess a 4-phase would have some other type of filter as well....perhape 2 different micron prefilters, one for large grit and one for microscopic grit. The sodium will pass through all of them unimpeded except for the R.O. membrane. The only way to bring the sodium right down to 0, or so close that you couldn't test for it, would be to put the product water from the R.O. through another R.O.....that is to have two R.O. membranes in line so that the water goes through one, creating waste water and product water. Then, plumbing the product water through another membrane....and again, producing waste water and product water. That's REALLY wasteful and you'll end up with so little product water in the end.

Also, beware of "water guys" who know how to sell water systems meant for people; but, have no clue about the needs of plants. I wouldn't be at all surprised it you were told that I am some dope who doesn't know what he's talking about because the sodium would be reduced to very low amounts that are well within tolerance limits for plants. The thing that they don't understand is how those low sodium levels are normally mixed with other elements, which balances things for the plants and they don't end up overdosing on sodium. Remember, when I was adding 10% of the raw well water back into the bucket of R.O. product water, I was not removing the sodium residue that was there; but, I was giving it a lot of competition from other minerals. Therefore, the plants didin't spend all their time taking up only sodium. They absorbed lots of other elements as well, reducing the total amount of sodium by displacing it. The R.O. product water that has been made with pre-treated water, while poisonous to orchids, will be a lot more pure as compared to R.O. water that has had 10% replaced with raw well water....but, by diluting the sodium with other nutrient elements, the sodium is rendered non-toxic. Pure water with nothing but a very, very tiny amount of sodium will kill your plants....don't let a water guy convince you otherwise.


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## McPaph (Sep 21, 2009)

Cant you put a holding tank (35,50,100 gallon) after the ro system with a float valve to shut off the water and a 1000 watt aquarium heater or 1 or two in line heaters somewhere else and plastic pipe it over to the conservatory and use a good water pump. Im assuming for a in line feeder. If not you could mix up your fertilizer in the holding tank. If you had enough room somewhere else you could put 2 tanks. One pure one mixed or one high ph and one low ph. Your plumber should handle that.


http://www.bigalsonline.com/BigAlsUS/ctl3684/cp18532/si1382456/cl0/hydoreth201inlineheater200w

Mick


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## Ray (Sep 21, 2009)

As RO systems have become a significant part of my business lately (forcing me to learn more), let me chime in a bit on this.

Unless you invest in a GE Merlin system, RO systems are not "on-demand" water supplies, so you're going to need a storage tank. A 100 gpd system operating with 77°F, 65 psi water, puts out about 1.1 cups of water a minute - certainly not enough to water with. If your feed water is in the 50's, it'll be less than 2/3 of that output - probably even lower, as that number is still at 65 psi water pressure, which is relatively high for a lot of homes.

As you'll need a storage tank, there is nothing to stop you from using a submersible ceramic aquarium heater to warm it up (a ceramic one won't be damaged if they accidentally operate out of the water). That's what I do - just ask aquarium store folks what size is needed for the particular tank volume and you're good to go.

In a typical 4-stage system, the water sees:

A sediment filter to get suspended solids out of the incoming water,
A carbon filter to remove most organics,
the RO membrane to remove the majority of dissolved solids, then 
a carbon "polishing filter" to catch any remaining organics.
A 5-stage filter adds a second carbon filter after the sediment filter, and they are recommended for folks using chlorinated water supplies, to lengthen the life of the membrane. (Thin film composite [TFC] membranes are degraded by chlorine, but are ubiquitous in the industry, so adding a second carbon filter is a simple preventive measure. Cellulose triacetate [CTA] membranes are not attacked by chlorine, but are getting more and more difficult to find, and have been reported to harbor bacteria.)

I'm at a bit of a loss about John's sodium scenario, as - unless your water softener is WAY overdosing the sodium - the amount passing an RO membrane should result in a far lower concentration than many folks have in their tap water, a level well below the phytotoxicity limits. (I have several customers running their RO systems off of a softened water supply, without issue.) Besides, most fertilizers have sodium ions in them - Dyna-Gro runs about 0.1 wt %, for example..

I don't understand the adding other ions makes sodium "non-toxic" either. I'd really like to learn more about the chemistry behind that, but letting that go for the moment, the vast majority of the time one is going to be adding fertilizer to the water anyway.


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## John M (Sep 21, 2009)

I'm at a bit of a loss about John's sodium scenario, as - unless your water softener is WAY overdosing the sodium - the amount passing an RO membrane should result in a far lower concentration than many folks have in their tap water, a level well below the phytotoxicity limits. *Ray, I believe I covered that scenario in my post. The problem is when there is ONLY sodium, even very low levels, in the water. Normally, tap water will have a mix of elements, including sodium. The plants can't concentrate on absorbing only sodium because the sodium ions are displaced and diluted by other elements. In my case, the R.O. was producing product water with nothing in it but very low levels of sodium and that was toxic with long term use. Some plants were okay; but, some sensitive plants, like Psychopsis, got very sick and never recovered.*(I have several customers running their RO systems off of a softened water supply, without issue.) *Well, there has to be something about their situation as compared to my situation, that is different. Perhaps they grow mostly plants that are more tolerant of salts; whereas, I had a lot of sensitive, mounted epiphytes.* Besides, most fertilizers have sodium ions in them - Dyna-Gro runs about 0.1 wt %, for example.. *Yes but, my point is with specific reference to when the R.O. product water was being used without the addition of fertilizer. The pure product water had ONLY sodium in it and that was the problem. My raw well water has sodium in it; but, when I added 10% back into the R.O. water, I not only introduced it's sodium to the R.O. water; but, I also introduced other elements like Calcium and Magnesium etc. and the plants thrived because the sodium was being displaced. Without those other elements, the plants absorb only sodium and even though it is in very low concentration, eventually, it reaches toxic levels in the plant's tissues. Remember, with respect to mounted plants, they were being misted with pure R.O. product water daily and only getting fertilezer every 2 weeks. So, that's 13 doses of low sodium to 1 dose of mixed elements in the fertilizer solution. The sodium sensitive plants didn't like that at all.*

I don't understand the adding other ions makes sodium "non-toxic" either. *Well, I don't think it made it non-toxic; but, it made it less available by simply displacing and diluting it. It's a balance thing.*I'd really like to learn more about the chemistry behind that, but letting that go for the moment, the vast majority of the time one is going to be adding fertilizer to the water anyway. *At the time of my water troubles, I was using pure R.O. water every day to mist and feeding just once every 2 weeks. When I added 10% raw well water to the R.O. product water, my plants thrived! I was a very GOOD grower. When I stopped adding the 10% raw well water and switched to using the pure R.O. water, over time, the plants, mostly mounted ones that were watered daily with the pure R.O. water, got very sick....especially anything in the Oncidium alliance.*


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## Candace (Sep 21, 2009)

I've used R.O. water coming from a softened line for 8-9 years with no problems. But, I rarely water with just R.O. as I tend to add something to it at every watering. I don't put hard water back in, but typically either fertilize or add CalMag etc. so maybe that's why I've not had any issues. And occasionally, I water with the regular, hard water landscaping hose when I'm feeling lazy. My misters run off of the regular hard water line as well. My TDS usually runs in the 0-3 range and if it goes higher I change filters. I think it's important when using R.O. to fertilize frequently anyway, since the water is so pure the plants need the nutrients. Using R.O. water and underfertilizing would eventually starve the plants, I'd imagine.


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## SlipperFan (Sep 21, 2009)

This is very interesting, and I thank everyone who has contributed to this thread. 

John, today I made contact with a different seller of RO systems. I printed off your posts and the ones following, and they were read with much interest. They promised to check with the manufacturer to see what the sodium content will be with the water analysis I gave him. They admitted they knew nothing about orchid needs, so they were very interested in what you had to say.

We'll see what happens -- I'll let you all know.


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## cnycharles (Sep 21, 2009)

john, there even could have been another prong to the fork hurting your plants; you say they were hurt because there was nothing else but sodium which over term hurt your plants. could also still have been the problem where very low ec water was actually drawing out nutrients from your plants in the exchange (though maybe that would have to be water running over the plants quite a bit to draw it off) just a thought. that would even tip the balance of good internal nutrients in exchange for sodium. i'm no chemist or plant physiologist, so that's just off the top of my head


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## John M (Sep 23, 2009)

cnycharles said:


> john, there even could have been another prong to the fork hurting your plants; you say they were hurt because there was nothing else but sodium which over term hurt your plants. could also still have been the problem where very low ec water was actually drawing out nutrients from your plants in the exchange (though maybe that would have to be water running over the plants quite a bit to draw it off) just a thought. that would even tip the balance of good internal nutrients in exchange for sodium. i'm no chemist or plant physiologist, so that's just off the top of my head



*Well, it's a valid theory to ponder and thanks for your input; but, I don't think it will fly. Orchids in general like very pure water because most of them are either epiphytic and get only dew and rainfall, both of which are very pure types of water; or, they are semi-terristrial and get their water from dew or rainwater seepages...again, quite pure types of water. Normally, the ec of the plant's internal fluids is higher than the ec of the water outside the cells, in the open environment. The pure water is absorbed through the process of osmosis, which is where low ec water naturally crosses a barier to dilute a higher ec. Thus, the plant absorbes moisture and is hydrated. When you water your plants with a high ec the oposite scenario happens....the moisture inside the plant crosses the cell wall barrier to the outside. Osmosis is the process of water crossing a barrier from low ec to high ec. That's why we call R.O. REVERSE Osmosis. Because of artificially applied pressure on the high ec side, the water is forced to cross a barrier from high ec to low ec, the REVERSE of what is normal for Osmosis.

Plus, your suggestion doesn't asnwer why my plants currently are all growing and thriving even though I still use pure R.O. water. However, as I said, I no longer use softened (sodium laden), water as feed water, I use unaltered, raw well water, straight from the ground, to supply the R.O. unit.*


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## SlipperFan (Sep 23, 2009)

John, how often do you have to change your filters and membrane? Also, what's the gallons-per-day output?


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## cnycharles (Sep 23, 2009)

John M said:


> Plus, your suggestion doesn't asnwer why my plants currently are all growing and thriving even though I still use pure R.O. water. However, as I said, I no longer use softened (sodium laden), water as feed water, I use unaltered, raw well water, straight from the ground, to supply the R.O. unit.



you answered your own question above... I understand osmosis and reverse osmosis. there are lots of plants, lots of different conditions. also how dry someone lets their plants get before watering again makes a difference in reactions, also the type and quantity of feed used per time and how often all makes a difference. what works great for one person may not work at all for someone else, so there is no golden bullet. also different municipalities use different amounts and types of chlorine type materials to sterilize water, different membranes remove or not different amounts of chemicals (different grades of membranes). also much water that is running down a tree is not very clean as you would put it, it's often pretty dirty either with powdered organic matter or believe it or not, material can evaporate from ocean water, turn to fog and then rain down on plants. I learned this this spring I think, reading a research paper about the amount of nitrogen and other material that was being supplied to plants in western south america near certain ocean currents; the plants were getting most of their nutrients from the rain and actually fog that was coming directly from the ocean. also if you have ever gotten irritated because you just washed your car and then it rained, the same thing happens to the plants after rain; they get dirty


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## John M (Sep 23, 2009)

SlipperFan said:


> John, how often do you have to change your filters and membrane? Also, what's the gallons-per-day output?



I stopped using sediment filters about a year ago. I save the money and it hasn't made any difference at all to the life or productivity of the membranes. The raw well water (@ ~ 55*F), goes directly to the membrane housing. I clean the membranes about once every 4 months with acid as previously described and I change the membranes about once per year. I have 3 - 75 gallon per day membranes; but, the output was pathetic. My line presure is only about 35psi; so, I had to instal an R.O. booster pump to the common line before it divides up into the 3 lines. Now, I get about 140 gallons per day.


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## John M (Sep 23, 2009)

cnycharles said:


> you answered your own question above... I understand osmosis and reverse osmosis. there are lots of plants, lots of different conditions. also how dry someone lets their plants get before watering again makes a difference in reactions, also the type and quantity of feed used per time and how often all makes a difference. what works great for one person may not work at all for someone else, so there is no golden bullet. also different municipalities use different amounts and types of chlorine type materials to sterilize water, different membranes remove or not different amounts of chemicals (different grades of membranes). also much water that is running down a tree is not very clean as you would put it, it's often pretty dirty either with powdered organic matter or believe it or not, material can evaporate from ocean water, turn to fog and then rain down on plants. I learned this this spring I think, reading a research paper about the amount of nitrogen and other material that was being supplied to plants in western south america near certain ocean currents; the plants were getting most of their nutrients from the rain and actually fog that was coming directly from the ocean. also if you have ever gotten irritated because you just washed your car and then it rained, the same thing happens to the plants after rain; they get dirty



Okay. You win.


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## Ray (Sep 24, 2009)

Dot - the standard recommendation of filter and membrane replacement is:

Sediment - 6 months
Carbon - 12 months
Membrane and polishing filter - 24-36 months.


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## Ray (Sep 24, 2009)

Concerning the contention that only having a single ionic species present in water increases its absorption may-, or may not be correct.

If we look at it from a purely osmotic pressure standpoint, one would expect the transfer rates of ions to be independent of one another:

If concentration [Ai]=[Ao], and [Bi]<[Bo] (ions "A" & "B", inside or outside the cell membrane), there would be no transfer of A, but there would be transfer of B into the cell, at a rate determined by the relative concentrations. The presence of absence of A should play no role in that.

However, I have always been of the impression that absorption was directly related to osmotic pressure, but in recent discussions with plant physiologists, I have learned that plants not only absorb mineral ions passively like that, they actually have active "pump" mechanisms to do so, even if the ion concentration inside the cell is greater than that outside. That nets three uptake scenarios:

Active - The plant absorbs what it can, up to a limit. Most mineral ions fall in this category.
Active - The plant pumps in all that it can, socking it away. I believe phosphorus is one of these.
Passive (the one I assumed) - the plant's absorption is directly related to availability in the root environment. Calcium and boron fall in this category.
Now, I don't know where sodium falls, but unless it is in the 2nd category - which it could be - minuscule concentrations should be of no consequence.


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## cnycharles (Sep 25, 2009)

education and continued learning isn't a contest, it's for all of us to continue and to help others along the way


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## John M (Sep 26, 2009)

cnycharles said:


> education and continued learning isn't a contest, it's for all of us to continue and to help others along the way



Could'a fooled me! The only point that it seemed you wanted to make was that I was totally wrong....and you used some pretty far fetched, unrelated analogies to "prove it".

I know what happened to my plants. I had water samples tested at a qualified, accredited agricultural laboratory. I had the results interpreted by professional horticultural scientists at my local government agriculture department. There was, is, and will not be, any doubt about what happened to my plants and why....and with that heartbreaking and valuable lesson in mind, I have made certain since then that the same "perfect storm" of circumstances was never repeated. As a result, I've never had another incidence of sodium poisoning again, even when I use pure R.O. water because I learned that the feed water can make a big difference! Argue all you like; but, I know that if you do exactly what I did, you're plants will die too....regardless of rainfall patterns in South America or whether or not you just washed your car.


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## cnycharles (Sep 26, 2009)

no, it was not my intention to prove you wrong, at least consciously. I speak mildly, but I guess maybe argumentation was read into my writing, which has happened before. I'm glad that your orchids are growing well, I was making points that there are sometimes other things going on, and there aren't magic bullets usually, though clean r/o water shouldn't usually be a problem. enjoy your well-growing plants

* sorry, the little light bulb just clicked on in my head this morning, and I realized that you (John) must have thought that my initial post to you was to detract from your observations that sodium laced (as it were) r/o water was poisoning your plants, and that my theories after that were meant to add to detracting from that point. actually, at that point and now I completely agree that this is the case! my point was that there could likely have been another way that the sodium water was poisoning the plants. the points I made about 'fog in central america', 'dirty rain on the car' and all that was to try and point out that it can be dangerous to make blanket assumptions that rain and water is always 'pure'. it is proven that rain and fog can lift and carry nutrients, minerals and what we class as pollutants and drop them on plants. one paper/magazine article I read stated that in some cases rain has been found to carry bacteria like pseudomonas from one water body or cattle refuse holding area to visibly pristine-looking waterways distant and with seemingly no way for the highly resistant bacteria to get there. wind seemingly whipped up the water with disease in it, and carried it up with the wind and deposited in previously unpolluted water. so the many words I typed in support of these points were wholly to back up my premise, that it is dangerous to assume that all fog, dew and rain are pure. I then and now still completely agree that sodium tainted r/o water can poison plants. 

one point I made about lots of very pure water leaching nutrients out of plants and soil is also true, and I listed observations of our water at work leaching nutrients out of leaf tissue in mass seedling and cuttings being rooted under mist; unfortunately these examples don't exactly compare to plants growing in the jungle or in our greenhouses that are getting r/o water. our cuttings have no roots to draw up nutrients from the soil or material, so pure water applied over and over do leach out material. also a tiny seedling in a tiny tray cell has very little usually non-soil media and very few roots, so pure water can leach material out of that supply system. when we added light seedling fertilizer to our misting water (that initially was very pure except for chlorine and fluoride), the leaching problem went away. orchids that are native to areas with high rainfall obviously are made so that they are somewhat protected from lots of water running over them by having waxy surfaces on top and the like. so, I shouldn't have used that example.. if I created confusion and lead you or others to think that I was trying to discredit your claims, then I apologize. it's clearly true that sodium can poison plants.


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## etex (Dec 29, 2009)

Great thread with lots of info! We just got our RO system running and the water is a little chilly-58.2 F, so I was looking into ideas for heating! Thanks!!


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## terryros (Dec 29, 2009)

I don't need a large volume of RO water at any one time. I get good heating of the water as a by-product of the electric pump I use for watering. The RO water goes in a 5 gallon bucket and I use an electric pump that you would use to drain a hot tup or pool cover, obviously connected to a hose. This pump generates heat, so I just turn the pump on about 1/2 hour before I am going to water and I have nice warm water. If you forget and leave it on too long, you will get pretty hot water (yes, I have done that).

On periodic days when I am thoroughly watering/feeding things, I may use upwards of 7-10 gallons of RO water. As the bucket gets down to one gallon left, I add more RO water and the combination of the cooler with the warmer water keeps the temperature in the 70-80 F range.


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## Shiva (Dec 29, 2009)

You'll need a pump to pull the water into your growing area. That pump can heat the water if left on for a while before use.


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## Rick (Dec 30, 2009)

Ray said:


> Concerning the contention that only having a single ionic species present in water increases its absorption may-, or may not be correct.
> 
> If we look at it from a purely osmotic pressure standpoint, one would expect the transfer rates of ions to be independent of one another:
> 
> ...



To make things even more complex..there is competition and facilitation of different ions across membranes when mixtures of ions are present (which there always is a mixture of some kind).


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