Need Help! Metal Stains Won't Stay Away

[TXGlenn]

This metal issue is driving me completely nuts. To the point where I'm wishing we never put in a pool.

I do the ascorbic acid treatment...bring down the chlorine, ph to 7.2, add ascorbic acid which takes the stains away immediately, add 1 liter of Metal Free 45 minutes later, let pump run 24-7 for ~ 2 days and then start bringing chlorine level up. About 10 to 14 days later, the metal stains start to reappear.

What is causing this?? I did this treatment about 4 weeks ago but didn't keep an eye on all my chemical levels but 2 weeks ago I did the treatment again and made sure everything was in-line on a daily basis (ph 7.2, TA 100, cyanuric acid 70, calcium is about 400 but has been since this was built). It's a 19000 gallon gunite pool with SWG.

Anyone have any ideas? Am I raising the chlorine too fast? I am really tired of buying all this ascorbic acid just to have the stains come right back. Thanks for your help.

[AFiremanFirst]

I don't mean to laugh!!! I've been there!!! Great regimen! However, I recommend a filter service before, and double your DE at recharge! Wow that will get some responses, but unless you've done this treatment please respect a little bit of experience. Perform your regimen, lower cl to 0. pH to 7.2-7.0, if you don't have a heater lower is arguably acceptable for short periods of time. Add your asorbic acid (aka vitamin C). Then a double dose of metal free. run for 48 hours, then another filter service and recharge at a normal rate. NOW, WITH ALL THAT SAID HEAR ME SAY THIS! Metal free is a sequestering agent that makes the small particles into larger particles that are often captured by your DE filter, if you are using a cartridge filter... I have not had as much success with the regimen. If you are using a sand filter, I don't recommend the regimen at all.

Keep in mind that as your water temp drops this winter your stains, which are more likely mineral stains rather than copper stains, are likely to move back into your pool water with your calcium deposits, and your pool is likely to be beautiful come janurary and feburary, this is because of the saturation index...

My very best advice to you is to do a drain and clean, but I understand the risk, and headaches associated with draining your pool.

[chem geek]

As was pointed out above, you need to keep the metal from redepositing on the pool surfaces and one way to do that is with filtration if your metal sequestrant is able to consolidate enough to get caught in a good filter. The problem with Metal Free is that it breaks down too quickly from chlorine so will release metal back into the water where it can then stain again. The better metal sequestrants use HEDP which does not break down quickly from chlorine. You can see these listed in this Pool School article -- ProTeam's Metal Magic and various Jack's Magic products.

Another approach you can take is to physically remove the metal by a chelation product that captures metals in a packet you then throw away. This thread talks about a recent product of this type, but I haven't used it myself and haven't seen enough reports on it to vouch for it, but in theory it should work as described. This might be a decent alternative if you don't have a DE filter. So you first do the ascorbic acid treatment, then measure the metal content of the water (which should be measurable), then use enough packets in the skimmer to handle this amount of metal, then after some weeks when you measure no more metal in the water, you throw away the packets.

[TXGlenn]

Thanks for the reponses! Sounds like I need to clean my filter (cartridges) as well as get a better sequestrant. I am intrigued by the chelation product though...I think I'll give it a shot.

Is there an inexpensive test kit for metals?

[chem geek]

Is there an inexpensive test kit for metals?

For drop-based tests, the answer is unfortunately no. The Taylor K-1730 for copper is $23, the Taylor K-1716 for iron is $59, the Taylor K-1264 that tests for both copper and iron is $92.

There are less expensive test strips such as this one or this one for copper and this one for iron, but I do not know if they are accurate. Additional test strips are offered here.

Usually you can take a water sample to a pool/spa store to get the water tested for metals.

[TXGlenn]

If the metals are deposited on the pool surface, will the metal test show a low-level reading? Is the best time to do a metal test after the ascrobic acid treatment?

[chem geek]

Metals deposited on pool surfaces won't show up in metals tests. Only metal still in solution will show up. So yes, it is best to do the metals test after the ascorbic acid treatment as the metals will then be in solution.