Reservoir ph keeps rising

Hey everyone, merry Christmas and all that jazz
For the last year or so I have been growing in coco so had to make a reservoir to hold the water. My problem is the ph rises awfully quick. I make my feed mix up and ph it to 6.0 then by the second water it's around 6.5 so I lower and the last water is back at 6.5, lower again, the next day it will be up around 6.8. I find it awfully tedious having to ph it 3 times a day every day. I run 4 airstones and a pump circulating the water from bottom to top. It is a drain to waste system. Am I doing something wrong? I've read that the ph rising is normal but I haven't read anything quite as drastic as I am getting. House and garden nutes with added cmx and nutrifield ph down. Thanks in advance

What’s your water source? Also in coco you want your ph to be 5.8. Your issue may also be 4 air stones, the water is off gassing CO2 which is making your ph raise. I set my ph to 5.5 and reset 12-24 hours later and it will remain stable until I use the res up.

biggiegallz said:

Hey everyone, merry Christmas and all that jazz
For the last year or so I have been growing in coco so had to make a reservoir to hold the water. My problem is the ph rises awfully quick. I make my feed mix up and ph it to 6.0 then by the second water it's around 6.5 so I lower and the last water is back at 6.5, lower again, the next day it will be up around 6.8. I find it awfully tedious having to ph it 3 times a day every day. I run 4 airstones and a pump circulating the water from bottom to top. It is a drain to waste system. Am I doing something wrong? I've read that the ph rising is normal but I haven't read anything quite as drastic as I am getting. House and garden nutes with added cmx and nutrifield ph down. Thanks in advance

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Your EC is too low, bump a batch up to at least 2.0 and above, it will probably hold. Also under LED it's better to have higher EC because plants eat up more since the spectrum is better.

SofaKingHigh_ said:

What’s your water source? Also in coco you want your ph to be 5.8. Your issue may also be 4 air stones, the water is off gassing CO2 which is making your ph raise. I set my ph to 5.5 and reset 12-24 hours later and it will remain stable until I use the res up.

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Sorry but wrong. CO2 in the water creates short-lived carbonic acid which lowers pH. Sounds like hard water that has unreacted carbonates after adjusting that dump more OH ions into the water raising the pH. RO water cures that.

biggiegallz said:

Hey everyone, merry Christmas and all that jazz
For the last year or so I have been growing in coco so had to make a reservoir to hold the water. My problem is the ph rises awfully quick. I make my feed mix up and ph it to 6.0 then by the second water it's around 6.5 so I lower and the last water is back at 6.5, lower again, the next day it will be up around 6.8. I find it awfully tedious having to ph it 3 times a day every day. I run 4 airstones and a pump circulating the water from bottom to top. It is a drain to waste system. Am I doing something wrong? I've read that the ph rising is normal but I haven't read anything quite as drastic as I am getting. House and garden nutes with added cmx and nutrifield ph down. Thanks in advance

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Water quality is most likely the issue here. As I mentioned above it sounds like hard water that has unreacted carbonates after adjusting that dump more OH ions into the water raising the pH. RO water cures that. When I was doing DWC for years it was normal to start with pH 5.5 and 3 days later when I topped up with RO before testing ppm and pH it would be 6.2. It was such a regular thing I'd only test every 3 or 4 topups. Every 3 days I'd boost the nutes back to my target after topping up with the RO then add 4 or 5 drops of conc. sulphuric acid to knock the pH back. Do whole grows without ever changing nutes. Save so much money. I used AN 3-part pH Perfect nutes so never checked pH but you must use RO or distilled water to pull that off successfully.

As your nutes are not in contact with your plants they can't affect the pH so it must be hard water problems.

With the airstones that circulation pump is overkill. I always grew in separate Rubbermaid tubs. 2 - 12" airstones laid perfectly in the groves on the bottom. 50L in a tall tub, 35 in the shorter ones at the right level to be an inch under the net pots. Half inch under that ridge for the5" pots and the same over the ridge for the 3.5" ones. Lids are the same size.

OldMedUser said:

As your nutes are not in contact with your plants they can't affect the pH

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It is carbonates affecting the Ph. My tap water is at 60 PPM with carbonates that always raise Ph and having an EC over 2.0 does counter over time the Ph swing. When plants are small it's easy to stay on top of Ph so plan is to stack up sooner than later to not worry when making gallons.

OldMedUser said:

Water quality is most likely the issue here. As I mentioned above it sounds like hard water that has unreacted carbonates after adjusting that dump more OH ions into the water raising the pH. RO water cures that. When I was doing DWC for years it was normal to start with pH 5.5 and 3 days later when I topped up with RO before testing ppm and pH it would be 6.2. It was such a regular thing I'd only test every 3 or 4 topups. Every 3 days I'd boost the nutes back to my target after topping up with the RO then add 4 or 5 drops of conc. sulphuric acid to knock the pH back. Do whole grows without ever changing nutes. Save so much money. I used AN 3-part pH Perfect nutes so never checked pH but you must use RO or distilled water to pull that off successfully.

As your nutes are not in contact with your plants they can't affect the pH so it must be hard water problems.

With the airstones that circulation pump is overkill. I always grew in separate Rubbermaid tubs. 2 - 12" airstones laid perfectly in the groves on the bottom. 50L in a tall tub, 35 in the shorter ones at the right level to be an inch under the net pots. Half inch under that ridge for the5" pots and the same over the ridge for the 3.5" ones. Lids are the same size.

View attachment 5355431

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How do you get that many bubble with 2 airstones? I have 4 and nothing like that. I also use tap water as I have no other option and yours was raising by 0.7 over 3 days, mine is doing that in 3 hours hahaha I must have terrible water?

OldMedUser said:

Sorry but wrong. CO2 in the water creates short-lived carbonic acid which lowers pH. Sounds like hard water that has unreacted carbonates after adjusting that dump more OH ions into the water raising the pH. RO water cures that.

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You clearly don’t know what you’re talking about, you prove I’m right with your own logic . CO2 has a direct correlation with the ph of the water. And yes CO2 when added to water does lower the ph, and then there’s Henry’s Law. You should go look it up.. So yes RO water would fix ph rising but if it’s tap water there will be an equalizing of gases and ph will rise until ph ceiling is reached. It’s very easy to just readjust ph 12-24 hours later and it will remain stable. Nutrients will also affect ph especially if your nutrients are organic based. The reason your ph is more stable with higher EC is because the nutrients your using are acidic. So that’s bad advice to just raise EC, I never go above 2.0 and have no issues.

biggiegallz said:

How do you get that many bubble with 2 airstones? I have 4 and nothing like that. I also use tap water as I have no other option and yours was raising by 0.7 over 3 days, mine is doing that in 3 hours hahaha I must have terrible water?

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It’s all about air pump size

My tap water is 8.2 PH ec .5 and acts alot like you said. If my two cents is worth anything as a newbie grower, this stopped when adding pool shock.

Believed to be bacteria related as the reservoir stunk and got cloudy. I seem to have plenty aeration with a wave maker. 60 gallon reservoir.

I thought I needed a ph controller for 500$ but as time went on running sterile dtw coco, it holds ph just fine for seven days.

NR613 said:

Your EC is too low, bump a batch up to at least 2.0 and above, it will probably hold. Also under LED it's better to have higher EC because plants eat up more since the spectrum is better.

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What is "better" about the LED spectrum?

I prefer to let my pH drift between 5.8-6.3. I'll set it at 5.8-5.9 add to res and leave it. No airstones just a wave maker aquarium power head provides the surface agitation required for oxygenation. When I top up the ph goes back down then slowly rises a few points through the next 2 days. No issue.
I always notice when I have air stones in the res the ph would rise rather quickly for whatever scientific reason.... so I don't use air stones anymore.

Most likely its from carbonates/bicarbonates if its tap or well. Drop your pH lower, try 5.6-5.8. If pH still rises you can go lower. There is a pH point where it will not raise back up, or at least not as fast. If that doesnt work it could be biological, if your rez feels, looks, or smells funny. If you are mixing a rez for days at a time you probably should use pool shock or bleach anyway.

Roguedawg said:

Most likely its from carbonates/bicarbonates if its tap or well. Drop your pH lower, try 5.6-5.8. If pH still rises you can go lower. There is a pH point where it will not raise back up, or at least not as fast. If that doesnt work it could be biological, if your rez feels, looks, or smells funny. If you are mixing a rez for days at a time you probably should use pool shock or bleach anyway.

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30% H2O2 (hydrogen peroxide) is a much better for the plants then chlorine. Peroxide only adds more oxygen for the plants and kills bacteria. I use 1ml per a gallon and I’ll do that every 2 days as my res lasts 5 days. You can do it more if necessary

SofaKingHigh_ said:

30% H2O2 (hydrogen peroxide) is a much better for the plants then chlorine. Peroxide only adds more oxygen for the plants and kills bacteria. I use 1ml per a gallon and I’ll do that every 2 days as my res lasts 5 days. You can do it more if necessary

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It's also orders of magnitude more expensive.

Calcium hypochloride breaks down into chlorine and calcium. Both of which are perfectly safe, and good for plants, in appropriate amounts.

A 1lb bag of pool shock lasts me almost 3 years, across a 27 gal res and a 17 gal res, running almost all year round, and costs 7 dollars plus shipping. A gallon of 30% h2o2 costs $50 at my local hydro shop, and lasts a couple months.

I would use h2o2 year round if it was reasonable for my budget, but only for the oxygen boost.

SofaKingHigh_ said:

You clearly don’t know what you’re talking about, you prove I’m right with your own logic . CO2 has a direct correlation with the ph of the water. And yes CO2 when added to water does lower the ph, and then there’s Henry’s Law. You should go look it up.. So yes RO water would fix ph rising but if it’s tap water there will be an equalizing of gases and ph will rise until ph ceiling is reached. It’s very easy to just readjust ph 12-24 hours later and it will remain stable. Nutrients will also affect ph especially if your nutrients are organic based. The reason your ph is more stable with higher EC is because the nutrients your using are acidic. So that’s bad advice to just raise EC, I never go above 2.0 and have no issues.

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I never said anything about raising EC. The effect of bubbling water on pH is so minimal it's not even worth considering. With hard water it will often rise after initial adjustment then again even after a couple more adjustments downward over a couple of day. Eventually it will reach equilibrium but the various minerals that were in the water are still there in a different form. This generally doesn't cause problems in a DTW system as any excess gets washed out every feeding. In a closed system like DWC or plants grown in pots those minerals will build up in time unless sufficient runoff, (approx 20%), is allowed to happen. In the case of DWC occasional water changes prevent the buildup.

The pH will rise slightly when aerating sue to initial outgassing of CO2 but once that reaches equilibrium it won't rise further. This seems illogical to me as when you are pumping in air it contains CO2 so it all should be the same as the water is absorbing all the gasses present in the air.

I do have a bit of a clue of what I'm talking about having grown my first buds in '78, growing and researching how to grow pot ever since then going back to school in my early 30s for 3 years to get a diploma in environmental chemistry. Since moving to northern Alberta here in '01 with 6 rooted hash plant clones there wasn't a day until a few months ago that there weren't pot plants under my care. Around 50 DWC grows under my belt since then and 100s of plants grown in pots of various mixes in the same period. Thousands of hours of practical experience and the same in reading about everything to do with pot. I am an insatiable reader and have been even before going into grade 1 at the age of 5. A month later I was 6 tho.

Henry's Law? Has nothing to do with the pH and only relates to how much of a given gas can be retained by the water for a given temp and pressure. All us pot growers need to know about that is colder water holds more O2, and other gases present in the pumped air, and warmer water holds less.

NR613 said:

It is carbonates affecting the Ph. My tap water is at 60 PPM with carbonates that always raise Ph and having an EC over 2.0 does counter over time the Ph swing. When plants are small it's easy to stay on top of Ph so plan is to stack up sooner than later to not worry when making gallons.

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60 ppm isn't really enough to have much effect on the pH due to alkalinity. That's not much worse than RO water from some systems. Generally with hard water problems can present when it's over 200ppm and many growers have tap water closer to 400 then all sorts of nasty stuff can happen to your plants. If on city water like that then a cheap RO system will get you lots of purer water for as low as $100. My tap water comes from a dugout on my property and is around 400ppm, depending on the season, and around pH 8. I have bought all the parts to install and higher end RO system but haven't got around to it yet. We already filter incoming water to 5µ so my system starts with a 1µ then a standard carbon filter to another carbon filter rated at 0.5µ before it hits the 75gal/day RO filter then to a UV sterilizing filter then a calcite filter to 'finish' the water adding some minerals back for drinking. I'll have a takeoff tap before the UV filter for water that will be used on the plants then another after the RO for water going into my BUNN coffee maker to prevent mineral buildup in it.



An EC of 2 or 1000ppm on the 500 scale would fry my plants over time due to our chronically low RH which causes the plants to use twice as much water as ones grown in an atmosphere closer to ideal VPD. This causes excess nutrient salts to be drawn up and stored in the leaves which eventually leads to toxic salts buildup that fries the leaves from the inside and rears it's ugly head about half way through flowering. Keeping my EC more around 1.0 grew lush green plants without negative effect. Took me a while to figure out what was going on but once I began feeding at lower levels the problem went away. In organic growing the plant has a lot to do with it's nutrient uptake but you can still burn plants with organics. Can really cause issues of burning when nutrient salts are used to supplement lower levels of available nutrients as the soil becomes exhausted.

I HAD THIS PROBLEM.. I was using ORGANIC PH REDUCER .. which with the air bubbles would degrade nearly instantly(within the hour) He gavve me PH DOWN meant for RDWC and never had to worry about it since... Also if not cooling the water it will raise. IMO everything else said here shouldn't be your problem.. EC etc etc etc .. nothing raises your PH so quick unless something is disolving your acids ..

biggiegallz said:

How do you get that many bubble with 2 airstones? I have 4 and nothing like that. I also use tap water as I have no other option and yours was raising by 0.7 over 3 days, mine is doing that in 3 hours hahaha I must have terrible water?

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Look at the pump I'm using to power that. It would do a 5 tub system quite nicely if not more and could aerate a huge rez for a large RDWC system.

You can contact the city/town that supplies your water and get a copy of their water analysis usually by email. As a user of their water it should be free. Have you checked the pH and ppm of your tap water? Even that will give you an idea of what you are dealing with. Tap water can be high or low in various mineral salts that can have a negative or even positive effect on the plants. Water too high in sodium can hurt the plants yet still be within range of potable water guidelines. Same with things like iron etc.

People on sodium restricted diets can have problems because of the water too and doctors rarely think about that. They cut all the salt out of their diet yet their blood pressure doesn't go down. This can cause iodine deficiency as salt is the only source of iodine for the majority of people. Low iodine leads to thyroid problems and goiters which are on the rise. As are thyroid cancers due to radioactive iodine in the air from things like the nuclear power plants in Japan that were severely damaged at Fukishima with the big tsunami that hit them about 10 years ago. If your thyroid is low on iodine when you inhale these hot particles, and we all do, it enters your bloodstream and is grabbed up by the thyroid planting a tiny radioactive seed in there that can lead to cancer. I add a drop of iodine to my mug of RO along with a dash of table salt an one of pink Himalayan salt as I have low blood pressure and that helps keep it up so I don't get so dizzy sometimes. No meds for that condition so salt and caffeine help to keep it up.

Tolerance Break said:

What is "better" about the LED spectrum?

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I listen to AROYA Office Hours, it's been covered a lot.