Metal Stains Slowly Returning

[fedman]

I have had my 45,000 gallon, concrete pool (cartridge filter;chlorine) for 5 years and have never had trouble with metal stains before. This year, I emptied the pool to paint it and had new water trucked in. I am fairly certain that the water that was trucked in is the source of my metals woes.

At the beginning of the season, I allowed my Cl level to run a bit high for a couple of days. At first, I thought that I had an algae problem because the color of the water was so dingy...brownish..., so I let the chlorine level remain high. Upon further inspection, the water was actually quite clear...the bottom of the pool had developed some dingy, brownish stains that gave the water the unpleasant color.

After I determined that it was metal stains, I ran through a Vitamin C wash (lowered Cl to 0...lowered pH to 7.0) and the stains disappeared. I placed 3 containers of Metal Free in during this process. I then slowly raised my Cl and pH and the pool looked great for a couple weeks. I have continued to add Metal Free (at least one 33.9 oz container a week), but the stains are slowly beginning to reappear....even when no new fill water was added. I thought that the new stains may have been organic because I have been keeping my Cl level on the lower side (I am really petrified to shock the pool for fear of more metal staining), but a Cl tablet does nothing to them while a Vitamin C tablet removes them. I know that I have a metal issue brewing again.

Any thoughts...Is the Metal Free product a waste of time? I know that it doesn't remove the metals from the water, but it is supposed to keep them suspended. I am not sure why the stains keep reappearing because I probably have placed 10 containers of the stuff in the pool since the acid treatment. The stains are much lighter than before I did the Vitamin C wash, so my wife and kids will swim in the pool....but they are driving me crazy. I have tried putting Culator pouches (any thoughts on these) in the skimmer and I am running fill water through a Metal Trap filter I purchased on the internet so as not to introduce more metals to the pool.

I have a feeling that most of you will come back saying that I will need to do another Vitamin C treatment to lift the stains, but I am attempting to avoid doing this since the swimming season in Ohio is not going to last much longer....really don't want to miss another week of good swim weather getting the water chemistry right again or chancing an algae growth with the lowered Cl levels. I am planning on doing a Vitamin C treatment at the end of the season...get all the stains off and sequestered in the water....then pump over half of the water out for winterization...hopefully eliminating the metal problem from occurring again next year.

If you have any other suggestions that could help my situation, please let me know. Is Metal Free a product that has worked for you or not? I have read that one of the Jack's solutions may work best, but will unlikely lift any of the stains I already have.

Thanks
fedman

Water is perfectly clear...83 degrees
CH-250
Alk-130
pH-7.4
TC-3.0
FC-2.5
Cya-80

[Watermom]

Instead of Metal Free, use an HEDP product. HEDP is a liquid phosphonate that is pretty chlorine stable, and very good at keeping dissolved metals IN the water, instead of ON your pool surfaces. It can lift recent stains, OR it can be used along with ascorbic acid, to keep the metals in the water, after the ascorbic acid is consumed by chlorine.

Jacks Magic The Pink Stuff 1qt (60% HEDP) @ Amazon
20% KemTek HEDP @ Amazon

You may also want to use some 60% polyquat which will allow you to keep your chlorine levels a little lower to help avoid more staining. (And with a CYA of 80 and low chlorine levels, you risk an algae bloom. So, it would be best if you did use some.)

See polyquat page for more info.

Kem-Tek 60% polyquat @ Amazon
Nava 60% polyquat @ Amazon

We have quite a few people using the Culator this season with good results. You will want to put it in the skimmer basket UNDER a skimmer sock to keep the Culator from getting all gooped up. At the end of the pool season, we would also like you to take pictures of your Culator pouch (outside and also cut it open and pictures of that, too) and send them to us at poolforum@gmail.com. We are trying to collect some information about how well they work.

I think your plan about enjoying the pool for the rest of the swim season and then trying to clean up the stains afterwards is a good idea.

[fedman]

Thanks. I wrote a response about each item above, but I keep getting blocked since I am a new member.

[Watermom]

I'm not sure I know what you mean. You can't follow the Amazon links?

[PoolDoc]

Unfortunately, "getting blocked" -- being moderated -- doesn't seem to be the issue here. Most likely, your post is lost. It happens to all of us -- mods, admin, team members -- occasionally. Personally, it usually happens to me, when I try to look back through a multipage thread, and forget to open the other pages in a new window, but simply page back. That loses the content of the edit window I was working on. But, there are multiple ways to lose you post, on with all flavors of forum server ware

Anyhow, it was never saved to the database here, so you'll need to re-write.

Sorry.

[PoolDoc]

Any thoughts...Is the Metal Free product a waste of time?

Yes, it's probably a waste of time, assuming that THIS:



is what you're talking about. I'm not sure what's in it; the 2005 MSDS indicates that at that time, it was EDTA. A newer 2010 MSDS indicates that it's a low concentration of citric acid. Here are snips from those MSDS sheets:

-

The problem is, neither EDTA nor citric acid are really chlorine compatible. I think they might work OK in a Baquacil pool -- EDTA is what's used in THEIR metal product, but basically you destroy the Metal Free when you chlorinate.

The sequence you have to follow to REMOVE iron stains like yours is
1. Lower chlorine
2. Add ascorbic acid (vitamin C) to dissolve stains + Polyquat to prevent algae while chlorine is low + HEDP to KEEP the dissolved iron, dissolved.
3. Re-chlorinate, destroying the ascorbic acid, which is then picked up by the HEDP, before it can restain.
4. Filter 24/7 with a CuLator in the skimmer, allow the CuLator to remove the iron from the water that contacts it. Some iron is also likely to be released, but end up in particles on the filter.

None of these steps work on their own. Using Vitamin C (or citric acid, through it's less effective) dissolves the iron, but then releases it to re-stain as soon as the pool is again chlorinated.

EDTA acts like HEDP, and can't really DISSOLVE iron that's already a stain, but it can keep iron in solution. However it's weaker than HEDP, and is MUCH more rapidly broken down by chlorine. So, using EDTA may *keep* iron from new water dissolved, but it can't dissolve iron that's already a stain, and neither EDTA nor HEDP do ANYTHING to actually remove the iron from the pool.

Likewise, the CuLator can't work alone. Iron in pool water tends to be rapidly oxidized by chlorine to a stain or particles -- so that when you add chlorine to water with iron in it, you QUICKLY* end up with water that has ZERO iron *in* the water. You may have terrible stains, but hardly any iron dissolved IN the water. Since the Culator ONLY works with dissolved iron, it's useless, unless you FIRST re-dissolve the iron, and then use HEDP to KEEP it dissolved in spite of the chlorine.

* an exception: bacterial nodular corrosion seems to involve enterobactin, an extremely strong chelant, much stronger than HEDP and possibly also quite chlorine resistant. In this case, you may have highly chlorinated water that ALSO has a lot of dissolved iron.

. . . I hope this is clear.