Iron Stain Returns

[BobbyC]

I did a vitamin C treatment last week to remove iron stains. Waited for chorine level to drop low. pH was 7.2. Added some polyquat. Everything was going fine until today when we received about 1 inch of rain. Now the stains have returned. I don't really think the rain has anything to do with it, but it's the first day that the chlorine level has held relatively stable for the last 24 hours. I only brought it up to about 2.5 which is the highest it's been since the treatment. My pool is 33,000 gallons and I added a quart of Metal Free after the stain treatment. I had already added 4 quarts of Metal Free prior to the treatment hoping that the Metal Free alone would take out of stain. I figured that would be an adequate amount of Metal Free since it's about twice the recommended amount.

OK, so now should I repeat the treatment and use more Metal Free? Or, did I raise the chlorine level too quickly? Or something else?

Current levels are:

TC 3
FC 2.5
CC .5
pH 7.4
TA 60
33000 gall Vinyl
Sand filter

Thanks,
BobbyC

[mbar]

No, you did everything right. Sometimes the stains return as soon as you start to add chlorine - you will have to add more sequestering agent and take your ph down to 7. Keep your chlorine steady. You didn't say how much cya you have. I would add baking soda to bring up your alkalinity first, then some sequestering agent - because sometimes the sequestering agent will lower your ph on it's own. If it doesn't, then you will have to add some muriatic acid or ph down. You should see the stain start to lighten after this. If they don't start to lighten after a couple of days, then just get a little more ascorbic acid and drop it near the stains. You don't have to do anything to your chemistry. Just keep an eye on the ph after this, and keep it around 7.2 for a while, don't let it get any higher. Keep adding chlorine to get it back to your regular levels. let me know how it goes, and if you have any other questions

[BobbyC]

You were right. The stains did pretty much go away after a couple of days. Is it really necessary to add the maintenance dose of the metal sequestering agent as recommended on the bottle? I'm in central VA where the humidity is high so I get very little evaporation, and thunderstorms usually keep the water level up, so I rarely have to add any water. Thanks for your help.

Bobby

[mbar]

No, I don't - I usually add it if I see some stain start to form - I take the ph down to 7 and add some. Sometimes just the matainence dose, or sometimes it takes a little more. It usually is after a lot of new water was added, due to rain or backwashing. You will get a feel for your own pool after a while.