organic rust?

[gwar9999]

I have a fiberglass pool surface & Pool Pilot chlorine generator (approx. 13k gallons). About a month ago I noticed a few spots of rust on the pool steps and at the bottom of the spa. The rust appears in small circles and is a dark orange. I've had success removing the spots with a vitamin C tablet. I did some extensive pool maintenance this past weekend and noticed the bottom of the pump basket was rusted. I also cleaned the Pool Pilot filter screen and noticed some rust on that too. Concerned, I went to the local pool supply store and had my water tested. Phosphates were a little high but nothing too concerning according to them (I've since lowered them) but they found no iron nor copper in the water. So I'm at a loss as to the cause. My pool isn't particularly dirty and any leaves or debris are removed weekly if not sooner. I suppose it's possible the rust could be organic in nature but I'm not sure what product to use and whether that product will remove the rust off of the pump basket and Pool Pilot filter screen.

Thanks for any advice!

 

[JasonLion]

The rust its self is just iron, like all rust. The best way to remove it is locally with vitamin c tablets or throughout the pool with an ascorbic acid treatment. For local treatment, put several vitamin C tablets in a sock and hold the sock against a stained area for 30 seconds to a minute. For a full pool treatment see this topic for directions.

Sometimes iron stains can be caused by locally high PH caused by organic debris, so iron stains are sometimes in the same pattern that the organic debris had. But the iron it's self doesn't normally come from anything organic. There are often trace amounts of iron in leaves and such, but not enough to matter.

 

[gwar9999]

Thanks Jason. I think I may have stumbled onto the cause from the link you provided-- often my chlorine levels are elevated which the pool store has never indicated as problematic but also my pH level rises quickly, at times. I have to add dry acid at least once/week to lower it from 7.8 (or even higher... I use the test strips so it's sometimes tough to decode the slight differences in colors between 7.4, 7.6, 7.8, 8.0, etc...). So I think the combination of elevated chlorine and pH levels is likely the culprit. I wonder though... since the only marks in the pool are tiny (and the vitamin-C tablet sock treatment will remove them) if I should go ahead and do the full ascorbic acid treatment since I noticed larger rust areas on some of the equipment? Also, the latter treatment says to "put the filter on circulate" means? I have a cartridge filter so does that mean I should remove the cartridge and just let the water pass through unfiltered?

 

[JasonLion]

Yes, in your case running on circulate means taking the cartridge out of the filter.

 

[gwar9999]

Thanks for the clarification Jason. I checked my pH and chlorine levels (7.6 and 0 respectively), removed the filter cartridge and added 1.5 lbs of the ascorbic acid. How long should it take to see any appreciable results? All of the rust spots remain after about 6 hours post-treatment and I've periodically brushed the affected areas. I don't want to leave the chlorine levels at zero any longer than necessary to achieve the desired results. Thanks and Happy 4th of July-- hopefully you're enjoying the holiday and not replying to forum posts all day.