Ta Keeps Creeping Up - Adding 1 Gallon Of Muratic Acid A Month

[DriveMeNuts]

Hello All -

I have a 35K gallon gunnite pool. Since opening the pool, I have been fighting an Alkalinity creep issue. My TA level is currently at 130 ppm. I get it to 100 (w/ PH at 7.1) and in about a month its near 150 ppm (PH 7.3). The pool is four years old. This is the first year requiring several acid treatments. I was not sure if this was normal as the plaster cures (not the right word) or if something else is causing the creep. Could I have metals in the water causing the creep? Any thoughts would be appreciated.

Thanks....

[chem geek]

The curing of plaster would increase the Calcium Hardness (CH) and the pH, but would only increase the Total Alkalinity (TA) via a small movement as the pH rose -- that is, lowering the pH with acid should bring the TA down to where it was. So your rise in TA is not from the curing of plaster. It is most likely from the fill water because evaporation and refill will add to the pool water whatever is in the fill water which is usually CH and TA. So measure your fill water to see if it is high in TA. Also, if you could use a pool cover, then that should significantly reduce the rate of TA rise.

I presume you aren't adding pH Up or Alkalinity Up product to your pool when the pH is low. If you add pH Up, that increases both pH AND TA and increases TA more than a pure base would because pH Up is sodium carbonate and is technically equivalent to a combination of a pure base, such as lye (caustic soda) and Alkalinity Up (baking soda). If you are using Trichlor pucks or otherwise have the pH low and need to raise it, then using 20 Mule Team Borax will raise the pH without adding to carbonates so has half the rise in TA. If you want to raise the pH with no change in TA, then aerate the water.

[DriveMeNuts]

Thanks....I am not adding any PH increaser. I have an auto safety cover on the pool. My fill water is good old fashioned well water that is high in PH and TA. That makes sense with the fill water. I have been adding more fill water this year than in the past due to the kids getting older resulting in more splash out of water. I'll keep an eye on it. Thanks again for the explanation and advice.

[billp]

Hello All -

I have a 35K gallon gunnite pool. Since opening the pool, I have been fighting an Alkalinity creep issue...

You do not say how you are chlorinating. If you have been using Trichlor tabs then the CYA is probably high. If you do not account for this when testing for alkalinity you will drive yourself nuts trying to keep it at the "recommended" level. The low pH suggests to me this might be the problem. Also, in my area if the pool cover is rarely opened we tend to end up with low pH/high alkalinity. To avoid this I have found leaving the cover off one day a week helps a lot.

Somewhere in this forum the details of CYA-alkalinity adjustment can be found. Maybe someone else will post the link, or if you search a little bet you find it.