Muriatic Okay With DE and CYA?


Well-known member
Apr 25, 2015
Pasadena, CA
I have a vinyl deck box out near my pool where I keep my Muriatic acid. It stays locked so the kids, pets and critters don't get into it. Just wondering if it's safe to also store CYA and diatomaceous earth in the same box? I've read some things are a no no, so just checking. Thanks.


Well-known member
Oct 21, 2015
My MA and bleach bottles have seals under the cap. So it is not possible for them to vent before the first time you open them.


TFP Expert
Platinum Supporter
May 23, 2015
Tucson, AZ
Pool Size
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
You can store acid with CYA and DE. There is no problem there. Bleach and acid MUST be stored separately. Bleach should NEVER be stored outdoors nor stockpiled for long periods of time as it degrades within months. It would be best to make sure your deck boxes are properly vented or else acid vapors can build up and be quite irritating.

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
San Rafael, CA USA
Full-strength Muriatic Acid (31.45% Hydrochloric Acid) has a high vapor pressure at higher temperatures. This paper and page 2-76 in this paper show that the vapor pressure of the acid at 40ºC (104ºF) is about 81 mm Hg or about one-tenth of an atmosphere pressure. Water vapor pressure adds another 18 mm Hg on top of that. So some bottles of Muriatic Acid have vented caps while those that are sealed need to withstand these or higher pressures.

Normally the "safer" Muriatic Acid that is < 25% or the half-strength that is 15-16% is in sealed bottles since the pressure is not nearly as high. The acid fumes significantly less. The half-strength has roughly 1/280th the vapor pressure from the acid while even 25% has 1/14th the vapor pressure from the acid.
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