First rule of TFP. Get a good test kit.
Second rule, based on your own testing, know what you are adding and why.
IF, and only IF, you have a Phenol Red pH test kit (those are typically readily available locally), then yes, you can use muriatic acid to lower pH.
HOWEVER...please download pool math and use it to calculate all your additions and for your pH reductions. Link-->
PoolMath
AND, only do it in .4 reductions. The chemistry is complex, and you can't calculate pH reductions accurately beyond .4. The phenol red test is not accurate above 8.
So, if you are going to reduce pH, test with your own Phenol red kit, confirm 8 or above. Use pool math to calculate a .4 pH reduction. Add the recommended amount of Muriatic with pump on. Pour slowly, like a 1 gallon in 2 minutes rate, directly over a return, with your pump running, then brush in that area...we don't muriatic to pool. 30 minutes later test again. If necessary, reduce again. Rinse and repeat until your pH is 7.4-7.6.
Also, no one will use the pool once it's brought back to life. It's my parent's pool & they aren't ever going to get in it again (their words, lol)
I'm cleaning it up for them so mosquitos & others don't breed in there.
Pools take daily maintenance and care. That includes testing (daily) and chlorination. If you have no one to do that, it may be time to remove the pool. Pools are like dogs. If you don't feed them, they die. Horrible analogy, sorry, but true.
