Do you adjust pH when watering?

[goodgollymissmolly]

That's a good question, Ross. There are numerous products out there for raising and lowering the pH of hydroponic solutions, aquariums, hot tubs, and swimming pools. Some of these are actually buffers. I do not wish to get into a debate with Ray again so I'll just say a buffer is a partially ionized salt, acid, or base. A fully ionized acid or base will lower or raise pH, respectively. A buffer will within limits try to maintain a constant pH. Vinegar (a 5% solution of acetic acid) is an example of a buffer. From rotten memory it buffers around 5, but don't quote me on that.
I got out of school a long time ago, unfortunately.

All these products add ions of various kinds to the solution. So when you use them you are raising TDS (or electrical conductivity which is a more precise, but harder to understand, measurement only because it uses rare units of measurement). So you need to know what ions you are adding when you use them.

A common pH down material is a weak solution of phosphoric acid, H3PO4. This a good choice for plants because the phosphate is usable by the plant. But, hydrochloric and sulfuric acids would be great to lower pH but rotten for the plants because they put undesirable ions in solution.

pH up materials are more variable. Potassium hydroxide would be a good choice but I have not seen it used. Instead I see such materials as sodium carbonate and potassium carbonate and citrate. I don't want sodium ions in my water (remember sodium chloride is table salt and kills plants). I also don't want the citrate ions, might just as well use acetic acid (vinegar) which is sometimes used as a herbicide.

It turns out that my water, while "hard" as Hades contains mostly calcium carbonate and magnesium carbonate. Both the calcium and magnesium are used by plants (in small quantities) and the carbonate acts to buffer the solution at pH above 7 (but if you don't put much in it can't get to 7 or above. My water is also pretty free of iron (which turns tea black in central Ohio and central Alabama) and sulphur (which smells to high heaven).

So what do I have...water that is OK for plants except it is too alkaline (pH 7.3) and contains too much dissolved solids (about 300 ppm but variable). It works great for raising pH and doing a little buffering as long as you can get both the pH and the dissolved solids that you desire at the same time. It appears I can balance that pretty well with a mixture of my rainwater with a little city water.

[IdahoOrchid]

Nice train of thought, Jim. How does one find out what the make up of their water is. Our water's TDS is even higher than yours is and is rock hard.

The house was run on straight well water for 5 years before we bought the house. We are STILL fighting little deposits breaking off the inside of our pipes from after we installed a softener 2.5 years ago. Our guest bath cold water barely trickles it is so blocked with chips. Our master bath just this last week spit out about a quarter teaspoon of chips and is FINALLY running full strength again.

[gixrj18]

I believe you can have your water tested at any of the water stores that rent & sell water softeners & reverse osmosis units. My water company sends me a report quarterly, fortunately......but I do believe those stores will test your water for you.

[Ross]

Originally Posted by IdahoOrchid

Nice train of thought, Jim. How does one find out what the make up of their water is. Our water's TDS is even higher than yours is and is rock hard.

The house was run on straight well water for 5 years before we bought the house. We are STILL fighting little deposits breaking off the inside of our pipes from after we installed a softener 2.5 years ago. Our guest bath cold water barely trickles it is so blocked with chips. Our master bath just this last week spit out about a quarter teaspoon of chips and is FINALLY running full strength again.

Culligen (and, presumably others) will do it for free. Of course you realize their motive is to sell (or rent) you a unit. But it may be worth it if you want that info bad. And who knows, maybe you'll want a new RO unit

[gixrj18]

I just got one, last week....man, what a difference. My water went from 326 ppm, to 6 ppm. It's a little more alkaline, too, the ph is in the low 8's. My tap water runs in the 7's. It still comes close to where I need it, after adding the nutrients, but I adjust it anyway.

[orchids3]

I understand that most aquarium supply places have pH test kits that are pretty reasonable. My pH/TDS meter has gone bad - most have a limited life - so will go in search of a test kit from that source. Has anyone tried it?

[goodgollymissmolly]

You will generally get a better price and more choice from a hydroponics place than an aquarium place. I guess pot producers demand lower prices than fish enthusiasts.

[Ray]

Goodgolly, you'll get no debate from me on buffers - it's been a long time out-of-school for me too!

Out of curiosity, why would you think H2SO4 would add undesirable stuff to the water?

[goodgollymissmolly]

Because as far as I know the sulfate ion is not something useful for plants. So if it is not useful it is a risk. There are a number of sulfate salts that are insoluble so why put it in there. Anyway...for pH down the choice of phosphoric acid is easy, cheap, and reasonably risk free because there is an existing, successful history of its use.

To give you a straight answer, I know of no specific data saying sulfuric acid does any damage.

[goodgollymissmolly]

OK, I went out this morning and collected a little more data.

I admit I just wanted an excuse to go to the greenhouse. It is bright and sunny with an outside temp of mid 20's F. Inside the greenhouse it's 66 F and in another hour it will be 75 and by noon I'll be running ventilation to keep it under 85. There is nothing better for my winter light disorder than the greenhouse. I wonder if Medicare will refund my construction cost?

I have been using some no name (repackaged) MSU formula pure water fertilizer. I ran out of GreenCare brand and picked this up at the Louisville orchid show. My new GreenCare stuff came in this week so I thought I would open it and see what results I get with it.

Mixed with rainwater I got:

1/4 teaspoon Greencare per gallon......6.0 pH
1 teaspoon of same per gallon............5.9 pH

As I reported yesterday, I got lower numbers with the no brand stuff. I'm guessing the GreenCare contains some buffering agent to adjust the pH to the desired range. So...I throw away the no name and use the GreenCare exclusively. Works for me!

I also checked the TDS of the GreenCare at 1 teaspoon/gal just for my own information. REMEMBER...TDS measurements are very temp sensitive and should be done at 72 F. I was closer to 65F so results will vary. With my TDS meter I got 670ppm and with my EC meter I got 1.1 uS/cm which converts to about 650ppm (although +/-50 is possible so the meters agreed within the accuracy you might expect. I went to Ray's page and calculated the expected TDS. He predicted 370 ppm using only the NPK constituents. My water is about 25 before I add anything so that makes about 400ppm and with the other ingredients in the fertilizer it's reasonable to get the total up to what I measured. The only reason I did this was to prolong the greenhouse session.

I do not recommend GreenCare or anything else. I'm just reporting what I did and hoping it's correct because I was careful to try to do it right. So I'm GreenCare in rainwater until I do something else. If you have something that works let me know and I'll probably change to it. There seems to be more than one way to get the desired results.