Huge amounts of copper in the pool

[haule]

I am new to this forum and pool chemistry, so please be patient.

I read many postings which are related to copper and iron in this forum, but I never saw anybody mentioning so huge amounts of copper (10ppm) as I have.

I own a pool for a few years and I was running it (I guess) OK until this year. At closing, I did not check PH level nor balance the pool and when I opened it a few weeks ago it was clear but completely out of balance. PH was below 6.5, alkalinity extremely low, hardness low, etc. The most frightening was the copper level of 10ppm. This must have come from the heater due to low PH over winter.

I first balanced the water, with keeping PH somewhat low around 7.2. The water was still clear. Then I added sequestrant (64 oz of super Sequa-Sol) and it turned the pool into milky color. I filtered the milky water through DE filter and it got clear again (took 48 hours of filtering). The copper level fell to 5ppm. Then I added another dose of
sequestrant (64 oz of super Sequa-Sol) and filtered for 48 hours. This time copper level fell to 2.8ppm.

I did not see any stains yet, maybe because I keep PH low around 7.2. I applied shock at the opening, and I did not see any staining or dark color in the water.

I am planning to repipe the pool such that I will pybass the heater and avoid future copper to eneter the pool.

I see that it will take many weeks to get copper down to acceptable levels of 0.2ppm.

My question is:
Is it worth the effort to keep adding sequestrant when the starting level of copper is so high (10ppm)? I read in this forum that sequestrant does not really remove copper but just binds to it. I filter out the milky water, but I am not sure how much copper is being actually removed with this filtering. The level of copper is dropping, but will I need to keep adding large amount of sequestrant all year long?

The alternative is to drain the pool and replace the liner. The vynil linear became white in many spots I guess because of low PH over the winter, hence it will need to be replaced eventually. I was hoping to postpone this for a year (costs around $3K in NJ), but does it make much more sense to just replace the linear and refill with the fresh water rather than spending money on sequestrant at the pool store.

Any help will be greatly appreciated.

[Watermom]

I have asked PoolDoc to look at your post for you. He'll be the best one to advise you on your situation.

Welcome to the Pool Forum!

[PoolDoc]

Sequa-Sol was a blend of citric acid and sodium hexametaphosphate, and possibly other stuff that they didn't have to list in the MSDS. I don't know if that's STILL what it is; manufacturers are not bound to keep a formula the same, and often reformulate without notice.

I don't understand why the pool would cloud after adding sequa-sol, unless your calcium was high. I don't understand why citric acid + SHMP would remove -- as opposed to sequestering temporarily -- copper. But, if it worked, it worked!

One possibility is that the cloud was calcium phosphate, which is very hard to filter UNLESS you have a DE filter. And, I'm pretty sure that copper will aggressively stain calcium phosphate surfaces. So, if you coat your filter with calcium phosphate, and the collect the copper on the calcium phosphate, and *then* clean your filter, voila', down the drain goes the copper.

But, that's a lot of guessing. Again, I don't really know what was happening.

Lemme go in a different direction for a moment. You don't quite say so, but you imply that the copper came from your heater. I *have* seen mega-copper levels where people with pool heaters let their pH get really low OR where they feed trichlor upstream of the heater. Copper only comes from heaters if something is badly wrong with the water chemistry inside the pool heater. THAT is something you need to fix.

[haule]

Thank you PoolDoc for your reply and suggestions!

Yes, you are right, my PH level was way too low over winter (possibly also in the fall) and I was putting chlorine tablets in the skimmer. I fixed PH and alkalinity now and I am not putting tables into skimmer anymore. I will bypass the heater and hopefully reduced the problem in the future.

You are also right that I have DE filter which I just replaced (Pentair 59023400 Complete Element Grid Assembly Replacement 48 Square Feet FNS Plus Pool and Spa D.E. Filter), because the old filter could not do the job anymore.

I am do not know if copper is only sequestered temporarily, or if maybe part of copper is indeed removed. Water testing shows lower level of copper, which could be due to both, I guess.

Is ia very bad to add so large quantities of sequestrant (12lb of super Sequa-Sol up to know and still adding)? Should I rather replace water?

Thanks!

[PoolDoc]

If Sequa-Sol is still SHMB, you *could* end up with very high phosphate levels, which could make your pool very 'twitchy' with respect to algae, turning green very quickly the first time you neglect chlorine levels a little.

Can you post K2006 levels for CYA, Alk and Hardness?

What I'm thinking is, if you keep your calcium high and your pH low, while using the SequaSol, you could possibly extract the copper on the calcium, and extract the phosphates with the calcium.

[haule]

Thank you very much PoolDoc!

Here are my test results:
FC: 4.5ppm
PH: ~7
TA: 100ppm
CH: 800ppm
CYA: 100ppm
CC: 0

I was stupidly following my pool dealer advice and was raising CH for no reason. Now is very very high.
The testing at the second pool store indicated a high level of phosphate, just as you predicted. I do not remember the exact number.
The pool is now quite clear (a bit milky but definitely swimmable). No problem with algae yet.

I will appreciate any advice.

[haule]

It seems you have some very nice trick to fix my pool water!

Maybe copper is really binding to CalciumPhosphate and since my DE filter is really good, I can filter out CaP in 48 hours.

What I do not understand yet, is your sentence "....to extract the phosphates with the calcium". How should I fix phosphate level now that the Cu level is dropping. I have a long way to go, but maybe I can survive with 1ppm of Cu and low PH?

Thanks!

[PoolDoc]

When you add the sodium hexametaphosphate, the bits that cloud the water are calcium phosphate, which gets filter back out. So you add PO4 in the SHMP, cloud the pool with CaHPO4, using H+ and Ca++ from the pool, and leaving the Na+ behind, then in the filter you attach Cu+ to the CaHPO3, possibly as CuCl2, and backwash it away.

So some of the phosphates you add as SHMP may end up leaving as a calcium phosphate + copper dust.

I'd recommend taking care of the copper first. Once the copper is to an acceptable level, you'll probably need to do a lime-softening run to lower your calcium somewhat. That will likely remove some phosphate, too. If you can aluminum sulfate available, you can remove more, using that. Once you've gotten the copper gone, the calcium to a manageable level, and then reduced the excess alkalinity, you can check and see if the REMAINING phosphate is at a level of concern.

[haule]

Thank you Doc!

I checked today with two different pool shops the level of phosphates and the level of copper. I do not have my own tests for that.

Both shops measured something around 100-200ppm of phosphates, and 2.4ppm of copper. It seems that the last 4 lb of sequestrant (super Sequa-Sol) did not reduce Cu level, but it was just adding phosphates. It could be that heater is adding copper at the moment, because I did not bypass the heater yet. I will fix that over the weekend and report.

As you suggested, lime-softening can be done with Ca(OH)2, but what form should I buy? Which substance can one buy to soften the water? Thanks!

I was very intrigued by the hardness test today at the pool shop. Most of their measurements agree with my own, except hardness test, which they got 108ppm (as opposed to mine 800ppm), and they suggested to add more Hardness control!!! I will recheck the hardness once more tomorrow.

[PoolDoc]

Probably the shops measured 100 - 200 ppb, not ppm. If I'm correct, that's nothing to be concerned about at present.

You can do lime softening with soda ash (NaOH). This explains it: http://www.poolforum.com/pf2/showthread.php?16992

If you get your pH above 7.2, and keep trichlor out of the skimmer, your heater will not continue to erode.