Pentair IntelliChem and Total Alkalinity

[SA Pentair User]

I have an IntelliChem unit on my pain pool at my beach residence which does a great job of controlling my ORP (chlorine and ozone) levels and pH levels.

My problem is that my alkalinity levels are always low. I simply can’t get them above 40 to 50ppm. I have tried both bicarb and soda ash. Both of them briefly raise the total alkalinity and the ph. The IntelliChem then takes over and adds lots of extra acid which wastes acid, gets the pH back in line and always brings the Total Alkalinity back to between 40 and 50. I’ve used numerous different test kits and they all give near enough the same reading, so my issue is not a bad test kit.

i have 5 other smaller pools across 2 properties (none of them, have the IntelliChem unit installed although I wish they did as the IntelliChem keeps the water looking beautiful and other than Alkalinity, they keep the chemistry looking great). I am able to get the Alkalinity to a sensible level of between 100 and 120 in all these pools. I am pretty sure the issue is the drip feeding of acid drops the Alkalinity levels too quickly?

My questions are:
1. Does total alkalinity matter when using the IntelliChem? I assume it does matter but the ph is very stable Amd has been for a few years so I don’t really get the need.
2. How do I get the total alkalinity level up?

 

[JoyfulNoise]

Alkalinity matters for not having your pH crash and cause corrosive damage to plaster and equipment.

We need more data to help you. Please provide a full set of test results for -

FC
CC
CYA
TA
CH
Salinity (if any pools use an SWG)

Also, what is the chemistry of your fill water - pH/TA/CH ?

An IntelliChem is going to dose acid in response to pH. Acid lowers both TA and pH. The reduction in TA is directly proportional to the quantity of acid added. pH reduction is a logarithmic effect that depends on the alkalinity on the water.

A TA of 100-120ppm is unreasonable in just about any pool. It’s an industry standard value but it’s not based on anything scientific or reasonable.

 

[SA Pentair User]

Thanks for the reply / interest!

FC = 3 (I also use ozone so ORP is probably more relevant - 650)
CC = 0.1
CYA = 30
TA = 50
pH = 7.6

not sure what CH is and I don’t use a salt chlorinator. Sorry. Being daft. CH is 250

 

[SA Pentair User]

I am wondering if I should be turning my IntelliChem off (stop the acid dosing) for a period after realising the alkalinity and if so, how long.

 

[JoyfulNoise]

it would be good to know your CH. Being in South Africa, we’re not as familiar with the water quality there. Your fill water is going to affect your pH and TA as evaporation and refilling will add a certain quantity of alkaline substances to the water. If your fill water has naturally low TA, then it’s harder to maintain a higher TA.

What are the points of pH for your dosing system. Unfortunately, IntelliChems are not really intelligent and Pentair tends to build in hard coded limits on what you can dose and when.

FC is much more important than ORP and ozone isn’t really that useful. A properly chlorinated pool will rarely ever need any form of supplementary oxidizer and so it’s mostly a waste of time and money on those systems.

 

[DavidLast]

Low TA could be balanced out using a higher CH. With a TA of 50, the dosing system won't add much acid, and you could balance it with CH as this will work fine in a chlorinated pool.

 

[pjt]

Is there a practical way of shutting the IntelliChem off so it stops dosing MA? Can you adjust the target pH it's attempting to achieve?

 

[SA Pentair User]

Low TA could be balanced out using a higher CH. With a TA of 50, the dosing system won't add much acid, and you could balance it with CH as this will work fine in a chlorinated pool.

Interesting. I was not aware of this. I will look into raising the CH.

 

[SA Pentair User]

it would be good to know your CH. Being in South Africa, we’re not as familiar with the water quality there. Your fill water is going to affect your pH and TA as evaporation and refilling will add a certain quantity of alkaline substances to the water. If your fill water has naturally low TA, then it’s harder to maintain a higher TA.

What are the points of pH for your dosing system. Unfortunately, IntelliChems are not really intelligent and Pentair tends to build in hard coded limits on what you can dose and when.

FC is much more important than ORP and ozone isn’t really that useful. A properly chlorinated pool will rarely ever need any form of supplementary oxidizer and so it’s mostly a waste of time and money on those systems.

Thanks again, CH is 250.

This pool is at my beach house and I am not there at present so cannot check the chemistry of the inflow water. Water quality in South Africa is generally not to bad. I know it is great at my main residence but have not checkedmy Beach Hose water quality. Will do that when I am next there.

pH setpoint is 7.6. I used to have it at 7.4 but I raised it to see if it would help with the current issue. The IntelliChem locks out adding acid when the oh goes above 8 (From memory).

I am thinking that I should turn the IntelliChem, off for an hour after adding the Alkalinity Increase or soda ash.

 

[SA Pentair User]

Is there a practical way of shutting the IntelliChem off so it stops dosing MA? Can you adjust the target pH it's attempting to achieve?

Yes and yes. I can change the pH setpoint.

Because it is a large pool, I have 2 circulation pumps and 2 filters Etc. But only 1 IntelliChem. I can thus easily turn off the one pump for, say, an hour after adding the Alkalinity Increase. This will turn off the IntelliChem also and the other pump will continue to circulate water. Not sure if this is a good idea and also not sure if an hour is long enough.

 

[DavidLast]

Our standard practice would be to isolate the dosing controller. Add the chemical. Wait one turnover time (typically) and then start up the chemical controller again. This may vary marginally for different locations and sometimes we may not be back until a day or three later.

 

[JoyfulNoise]

Low TA could be balanced out using a higher CH. With a TA of 50, the dosing system won't add much acid, and you could balance it with CH as this will work fine in a chlorinated pool.

CH has nothing to do with alkalinity. Calcium hardness is the measure of the concentration of calcium ions in solution, or, if you don't have a good test kit, total hardness is used and that measures calcium plus magnesium ion concentrations. When dealing with issues of pH, additional calcium hardness will make no difference.

Interesting. I was not aware of this. I will look into raising the CH.

Please don't raise your CH. The above advice is incorrect.

The issue you have is that the acid dosing system is simply responding to the pH value of the water and dosing acid until the pH gets to the set point value. The acid is consuming alkalinity and will do so until the alkalinity is decreased to the point where the effects of carbon dioxide outgassing (causing pH to rise) are balanced against the addition of acid.

All water that has any dissolved inorganic carbon (DIC) in it will always have rising pH and an equilibrium pH value. The dominant carbon species for pool water is the bicarbonate ion. The pKa for bicarbonate is around 8.4 . Therefore, with any appreciable amount of bicarbonate in the water (and all surface waters and well waters in the world have dissolved bicarbonate), the pH will always tend to rise above 8.0. It isn't until the carbonate alkalinity drops below about 20ppm or so before the pH of water starts to drop.

The real fix here is to limit the range of pH on your IntelliChem. Allowing your pH set point to be set at 7.8 means that the IntelliChem will not dose acid until is above that point and the amount of acid dosed to drop it lower than 7.8 will be pretty minimal. That will have the least amount of impact on your TA.

 

[SA Pentair User]

.The real fix here is to limit the range of pH on your IntelliChem. Allowing your pH set point to be set at 7.8 means that the IntelliChem will not dose acid until is above that point and the amount of acid dosed to drop it lower than 7.8 will be pretty minimal. That will have the least amount of impact on your TA.

is a pH of 7.8 not a little high?

 

[JoyfulNoise]

is a pH of 7.8 not a little high?

Nope.

One of many pool industry fallacies. When CYA is present in the pool water, active chlorine variation with pH is much less important. In fact, it doesn’t really matter at all.

Now your problem may be with the IntelliChem and that it will not allow your pH to go above or even near 7.8 because that will mess up the ORP signal. Some of the manufacturers hard-code certain chemistry limits into the system making it hard to impossible to deviate from. Another reason why TFP really doesn’t support the use of these chemistry control systems.

 

[DavidLast]

ORP/pH controllers are complicated at times. Yes, a higher pH will often cause the ORP to fall and the chlorine to overshoot the targets. It may be wise to set the ORP target very low, let the pH come up first, manually add chlorine to the desired level and then tune the ORP target to the displayed value. However, even then, there may be constant adjustments of the ORP to hold the chlorine level in some pools.