Notes on watering a mixture of rain water and tap.

[garysan]

Read a couple of articles that mention mixing a percentage of tap/city water with rain or RO water in order to get a more balanced watering (adding back calcium and/or magnesium to 'pure' rain/RO water). I'd be curious to hear of people's thoughts and/or recepies for such while I get my new regime for watering and feeding dialled in properly. Thanks

 

[Ozpaph]

Rainwater + fertilizer, done.

 

[abax]

The mixture depends on what type of plant I'm watering.
For Phrag. species I use rain water and for Paphs. and
species Phals. I use tap primarily. Fertilize once a week
with K-Lite and tap.

 

[Stone]

You could use straight tap water and possibly adjust the pH if necessary.
You could mix rain and tap to get your Ca.
You could use straight rain water provided it was clean and your fertilizer contained sufficient Ca S and Mg.
You could use straight rain water and add dolomite or lime to your mix.

All these are done and all are successful.

 

[Ray]

If your fertilizer contains calcium and magnesium, why would you need to add more via tap water?

 

[JAB]

I suppose it is human to try and make a blanket, easy statement about one thing versus another. Their are a number of factors that should go into such a decision. For instance rainwater is great... unless you live down wind from a processing plant, or in a place like say... Beijing! Tap water varies even within jurisdictions (look at Flint).
I think the best approach is to get a PPM/PH meter and constantly test the various water you are going to use. Supplement where needed but not more so.

Just my two cents
***

 

[garysan]

Worth measuring so here we are:

My rain water is currently PH: 6.8 and TDS: 13
With OrchidFocus fert added at 1/2 strength it changes to: PH: 5.9 & TDS: 139

Consequently, my tap water is PH: 7.2 & TDS:366.

I suppose it is human to try and make a blanket, easy statement about one thing versus another. Their are a number of factors that should go into such a decision. For instance rainwater is great... unless you live down wind from a processing plant, or in a place like say... Beijing! Tap water varies even within jurisdictions (look at Flint).
I think the best approach is to get a PPM/PH meter and constantly test the various water you are going to use. Supplement where needed but not more so.

Just my two cents
***

 

[phraggy]

Hi Gary. Your rainwater plus fert is absolutely perfect . If you have enough rain water I wouldn't consider using water from the tap. I use RO water plus Akernes Rain Mix and the day after I leach with RO plus a little Seaweed extract, I water with this regime every day, I can do this because all my multis are on heated sandbeds ( kept moist ) with strong air movement and planted in a very loose bark and perlite mis and also planted in baskets. I water in the morning and they are almost dry the following day
Ed

 

[gonewild]

Worth measuring so here we are:

My rain water is currently PH: 6.8 and TDS: 13
With OrchidFocus fert added at 1/2 strength it changes to: PH: 5.9 & TDS: 139

Consequently, my tap water is PH: 7.2 & TDS:366.

Do you know the content of the OrchidFocus fertilizer?
It is N2.2 : P1.3 : K2.1 : 2.5Ca
Very dilute fertilizer, when you purchase you pay mostly for water.

The calcium content is greater than the nitrogen content. Based on that alone there is no need to add tap water.

2.2 : 1.3 : 2.1 is the same NPK ratio as 22:13:21 in a standard blend fertilizer.

When you apply at your half strength you are adding 126ppm of fertilizer.
So 126 x 2.2% = 2.7ppm nitrogen supplied when you fertilize your plants.
That is basically nothing.
OrchidFocus does not even have enough magnesium to give it an position on the label.

What all this leads to is that they use tap water to make the liquid they sell and whatever is in their tap water makes up the bulk of the minerals you are applying.

The answer to your question is don't add tap water.
The reality is that the OrchidFocus is so weak it probably does not matter if you use RO or tap water or a mix of both.

 

[C. Rothschild]

I have heard that rainwater's the best but realistically whatever bucket or however you collect it in will have dust or residue in it. Might not matter though. If you do mist your plants I'd say rainwater.

 

[Redtwist]

Do you know the content of the OrchidFocus fertilizer?

What all this leads to is that they use tap water to make the liquid they sell and whatever is in their tap water makes up the bulk of the minerals you are applying.

The answer to your question is don't add tap water.
The reality is that the OrchidFocus is so weak it probably does not matter if you use RO or tap water or a mix of both.

This is interesting. I don't usually get too scientific about the water, but as I use OrchidFocus, I now wonder if it is the rain/tap water content and occasional epsom salts/dolomite lime that is feeding the plants, rather than the feed itself.
(At least they seem to be doing ok at the moment, whatever it is!)

 

[gonewild]

This is interesting. I don't usually get too scientific about the water, but as I use OrchidFocus, I now wonder if it is the rain/tap water content and occasional epsom salts/dolomite lime that is feeding the plants, rather than the feed itself.
(At least they seem to be doing ok at the moment, whatever it is!)

It's probably a combination of both. The rain water may have some nitrates in it too.
It's only my opinion but in a situation like yours where the plants grow well with so little nutrients I think there is a high population of nutrient producing living organisms. The organisms decline as certain nutrient salts increase.

The OrchidFocus has a high calcium content which likely means the nitrogen source is from calcium nitrate. It also has no UREA which for me is a good thing.

Your question was about mixing tap and rainwater which I gave you my opinion about. If you are thinking of ways to improve growth your first step could be to simply increase the strength you apply the OrchidFocus at.

 

[Redtwist]

Hi Lance
I think you are mixing up myself and garysan, who started this thread. I was just commenting because I also use OrchidFocus. But thanks for the info - its all 'food' for thought! oke:

 

[gonewild]

Hi Lance
I think you are mixing up myself and garysan, who started this thread. I was just commenting because I also use OrchidFocus. But thanks for the info - its all 'food' for thought! oke:

Are you sure? :wink:

 

[Redtwist]

'I was confused, but now I just dont know.' :wink:
Chris

 

[garysan]

All information is good. I'm getting really good root-growth and new growth from both my paphs and phrags. I just want to do the best job by my plants and wondered if there was room for improvement. My paphs all seem very happy and lots of them are/have flowered. Some of the phrags though are still licking their wounds from whatever was going on when I used the RainMix previously; others seem unaffected. I'll stick to what I'm doing currently - if it ain't broke....

It's probably a combination of both. The rain water may have some nitrates in it too.
It's only my opinion but in a situation like yours where the plants grow well with so little nutrients I think there is a high population of nutrient producing living organisms. The organisms decline as certain nutrient salts increase.

The OrchidFocus has a high calcium content which likely means the nitrogen source is from calcium nitrate. It also has no UREA which for me is a good thing.

Your question was about mixing tap and rainwater which I gave you my opinion about. If you are thinking of ways to improve growth your first step could be to simply increase the strength you apply the OrchidFocus at.

 

[naoki]

When you apply at your half strength you are adding 126ppm of fertilizer.
So 126 x 2.2% = 2.7ppm nitrogen supplied when you fertilize your plants.
That is basically nothing.
OrchidFocus does not even have enough magnesium to give it an position on the label.

I think this fertilizer is liquid, so your calculation is not right, Lance. oke:

 

[gonewild]

I think this fertilizer is liquid, so your calculation is not right, Lance. oke:

Why? If it's wrong correct it please.

garysan increased the ppm of his irrigation water by 126ppm by adding nutrient salts.
All of the increased PPMs came from the fertilizer solution.
According to the fertilizer label the salts he added contained 2.2% N.
Therefore 2.2% of the PPM increase is nitrogen.

Makes no difference to the math whether the source of PPMs is liquid or dry.
Does it?

 

[consettbay2003]

Personally I would not use a fertilizer that did not contain a decent amount of ammonium or urea as a source of nitrogen.

 

[naoki]

Why? If it's wrong correct it please.

garysan increased the ppm of his irrigation water by 126ppm by adding nutrient salts.
All of the increased PPMs came from the fertilizer solution.
According to the fertilizer label the salts he added contained 2.2% N.
Therefore 2.2% of the PPM increase is nitrogen.

Makes no difference to the math whether the source of PPMs is liquid or dry.
Does it?

Sorry, Lance, I didn't mean to be cryptic, but it does make a difference. In the liquid form, you are forgetting that water is already in the stock solution (water isn't considered as "solid" in Total Dissolved Solids).

Maybe an example may help. For simplicity, let's say that we start from 22% N solid fertilizer. You put 100g of this and fill it up to a liter of water. Now this is the stock "liquid" fertilizer with 2.2% N (I'm using weight/volume % here). But when you only look at the solids in this stock, 22% of "solid weight" is N (not 2.2%). So you should have done 126ppm * 0.22 (=22%) = 27ppm. But we don't know what was the original composition. So this is just an approximation.

Or here is alternative way to think. TDS of of this hypothetical stock (with 2.2%N) is 100,000 ppm. So to get TDS of 126ppm, you need 793x fold dilution. If you dilute 2.2%N with 793x dilution, you get 22000ppm (=2.2%N)/793 = 27ppmN.

Estimated TDS (126ppm) from EC is not really the actual TDS, so it is just a rough approximation without knowing how many ml of OrchidFocus per liter is used (it is difficult to understand what "half" strength means as Ray always points out).