Recurrent Metal Staining (have read other posts)


New member
Sep 10, 2020
Hoping someone can assist. I have a 30,000 gallon in-ground vinyl salt water pool with recurrent yellow metal stains on pool floor/ walls. Is there any way to check if metals are coming from heater? All pool water goes through heater regardless of use- no way to bypass (I only use heater for spa which I rarely use). I do have well water, but this year have used metal filters with garden hose when topping pool off (use two filters, EcoOne Hose Filter and Pleatco PPS2100). I have treated multiple times with ascorbic acid this year which removes all stains quickly, followed by initially Proteam Metal Magic, later switched to Natural Chemistry Metal Free as pool phosphate level went well over 4000 (the cut off on test). Stains generally recur 1-2 weeks after ascorbic acid treatment despite use of Metal Free (and prior Metal Magic) and CuLator packs (I use three - CuLator 4 in filter pump basket, and CuLator 1 in both skimmer baskets; current CuLator packs still puffy with some yellow/ brown discoloration; have replaced the CuLator 1 packs once this year. CuLator 4 added about a month and a half ago). I have not used algaecide, have stopped shocking pool (which turns water green), and have kept chlorine level between 1 to 2 with salt/ chlorine generator. Water has been clear without algae this summer (had this problem last year as well, before switching to salt water this year).

The pH of pool water generally runs high (7.8 to 8), but I have been keeping this down, around 7.5 since last ascorbic acid treatment two weeks ago with occasional dry acid (I understand that higher pH can promote surface staining, and low pH can promote corrosion in heater, leaching metals into water).

Stains still come back. Any suggestions? Is there a way to see if this is coming from heater (Raypak P-R406A-EP-C , approx. 10 years old)? For what its worth, elevated levels of copper/ iron have not been detected in testing at pool stores- possibly due to sequestrant/ chelator and testing for only free metals?



Gold Supporter
TFP Guide
Jul 21, 2013
Northern NJ
Pool Size
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
Welcome to TFP.

AA treatment raises iron stains from the pool. A deteriorating heater core is copper. It does not sounds like you are getting copper stains from your description. I would go looking for the source of your iron.

Tell us about your pool. Please create your signature with details of your pool and equipment. Some old pools used iron pipes int he underground plumbing. Are you using any mineral cartridges like Nature2?

I don't know what you have already read so here are some links about iron and copper in pool water...

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