Muriatic Acid in a Fiberglass Pool


Active member
Jun 30, 2009
I just read the following (cut & paste):
Muriatic acid is heavier than water and may etch the plaster in a shallow pool. To eliminate this possibility, pre-dilute the acid first by adding the acid into a large plastic bucket of water, and then pour the acid solution into the deep end of the pool, away from skimmer and fixtures. Muriatic acid is NOT recommended for vinyl-liner, painted or fiberglass pools.
Is this true? I just installed a fiberglass pool and have been using (for the past month) Muriatic Acid. If I can't use that, what should I use?


TFP Expert
LifeTime Supporter
Feb 23, 2008
Denton, TX
You may use MA in a vinyl or fiberglass pool. The key to avoiding problems when adding the acid is by adding it very, very slowly, in front of a return jet while the pump is running. Then, after adding it, allow the pump to run for an hour or so more after adding it. You want to ensure that the acid has had ample opportunity to mix thoroughly in the water so that it doesn't collect on the pool floor and cause problems.

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
San Rafael, CA USA
Also, if you think some of the acid hasn't hit the return flow and mixed, for extra safety you can lightly brush the side and bottom of the pool in the area where you poured.

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