Iron Staining


Well-known member
Oct 14, 2009
I have been fighting iron staining since my pool was installed (about 1 year ago). I have spent a fortune on staining products including AA. I accidently found that I can use PH down and sprinkle it down the side of the pool in the stained area. It works!! Then, if the ph gets too low, I add a little alkalinity (baking soda). I have found that if I keep my ph low (around 7.2) and my chlorine in the low normal range that the staining is less of a problem.

Is there any problem with using the ph down product to help with the staining? It is less expensive. I have a fiberglass pool and I do not want to mess up the gelcoat.

Thanks for your help!!



TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
Silver Spring, MD
Doing this with only a small quantity of PH Down in any one spot at one time, and being sure to run the pump for an hour or more afterwards, is fine. If the PH Down ever accumulates on the bottom of the pool you are likely to have problems eventually.

Your approach is sound, but won't work in all situations. PH Down is most effective on new stains, and will often fail to work on stains that have been there for a while.

There are two ways to prevent stains from returning. One is careful management of the PH, so it always stays around 7.2. The problem with this approach is that it only takes one failure of attention for the PH to go up and the stains to return. The other is to use sequestrant to hold the metals in solution so they can not cause stains. Unfortunately, sequestrant breaks down over time, so you need to be constantly adding more, which can get expensive.