What is the least expensive acid additive?

greenpoolnomore

New member
Jul 4, 2012
3
Livermore, CA
My pool CONTANTLY needs acid to keep the pH in normal range. Just put in 2 gallons of muriatic acid that cost $11.00 two days ago and the pH is back up to 7.8 today. Is there a less expensive way to drop th pH?
 

JasonLion

TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
37,880
Silver Spring, MD
Welcome to TFP!

Muriatic acid is almost always the least expensive by a wide margin. That is about the going price for 31% muriatic acid, though I have seen it for just a little less than that occasionally.

How do you end up needing to use so much acid? We might be able to help you adjust things so you don't need to use as much, though there are some situations, like fresh plaster, where there is no avoiding it.
 

JohnT

Admin
Mod Squad
TFP Expert
Apr 4, 2007
9,536
SW Indiana
I find MA price varies quite a bit. I can find it for $3.89 a gallon at a farm store, but hardware stores usually run $6.99 or more.
 

greenpoolnomore

New member
Jul 4, 2012
3
Livermore, CA
Total Alkalinity is VERY high at 130. The pool chemical place intown says that only way to deal with that is to add MA. Perhaps I should be looking at cost effective alternatives to reducing TA rather than to reduce pH? We are on well water so that may have something to do with the weird readings of our pool water. Water coming into the house goes through multile steps of softening and filtering but the pool water comes directly from the well.
Results from the modt recent pool water test are:
FC=5
TAC=5
Cya=100
TA=130
pH=7.8
Copper=0
Iron=0
Total Dissolved Solids=900
Phosphates=200
Pool is green even with daily vacuum/scrub of pool walls and bottom and rinse of filter every 12 hours. The algae thinks this is really fun that they have stumped me.
 

JohnT

Admin
Mod Squad
TFP Expert
Apr 4, 2007
9,536
SW Indiana
for CYA of 100, you don't have nearly enough chlorine. Lowering alkalinity requires MA, but the pool store method won't work. You have to use it to drop your pH to around 7 and keep it down there routinely while aerating the water.
 

JasonLion

TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
37,880
Silver Spring, MD
You need to lower CYA down to something reasonable (50 or 60) and then shock the pool. One thing to watch out for is that the common CYA test will report any CYA level over 100 as 100, so your CYA level might actually be much higher. With CYA that high it takes really extreme amounts of chlorine to fight algae, so much that it becomes completely impractical.

There are full instructions on lowering TA, which will stop the PH from rising, in Pool School.