Shocking/Staining

[DesertGators]

We are still relatively new to maintaining a pool, and we had to clear a little algae in early July. Toward the end of the shock treatment the pool developed brown staining rather suddenly. It is in a radiating pattern from the pop-ups, and an internet search made me wonder if the PH drifted up too much during the shocking process, resulting in stains. I added a bit of acid, hoping to keep it from getting worse. PH was in the normal range when FC levels came down enough to test. I have read various posts over time about vitamin C, tri-chlor tabs, and sequestrants, but I am hoping someone won't mind giving me the cliff notes version of potential causes of brown staining, and what might be done.

I do not have my hard numbers from that time, but variables that might help: We were performing the CYA test wrong, and I think our shock levels were higher than our FC/CYA chart recommends (shocked for 55-60, actual CYA closer to 40). I can't imagine too much FC would turn a light colored pebbletec brown, but who knows. We have upward PH drift, requiring MA every 2-3 days to keep it 7.5-7.8. Our TA sometimes peaked at about 90-100 before coming back down to 70-80. We do have hard water here, and despite a complete drain/fill this spring, we are sitting at about 380 CH.

I am currently trying to adjust the CYA to control chlorine loss during our 100+ days, but I would also like to add borates soon. I just need to figure out whether staining is something I should tackle first, or if all of these things can happen simultaneously. We have company in two weeks, and I need the pool balanced & ready. Thanks!

 

[duraleigh]

Identify the stain as either organic or metal (iron, probably)

1. Hold a tri-chlor puck on it for a few minutes - if it gets better, it's organic

2. Hold a socked of crushed vitamin C tabs on it for a few minutes - if it gets better, it's iron

Report what you find.

 

[BoDarville]

Welcome to TFP!

Staining such as you have described is almost always caused by metals in the water. If you use well water to fill your pool, that is almost always a source of metals (particularly iron). Another source of metals is current or past use of algaecides containing copper or other metals. Copper is also present in many "mineral" systems and ionizers and some trichlor pucks usually labeled along the lines of "includes algaecide".

When metals are present in the water, it is common for them to suddenly appear when chlorine is added or increased as well as when the pH is raised as you have experienced.

If the staining is only in isolated spots, you can rub a Vitamin C tablet on the stains. If the staining is more widespread, you can perform an Ascorbic Acid Treatment.

Short of draining water and refilling with metal-free water, there is no practical way to remove the metals from the water. One thing you can try while performing the Ascorbic Acid Treatment is the "paper towel" method which involves putting put some paper towels in a skimmer. The paper towels may capture some of the metals, but there are no guarantees. However, it is a low-impact, low-cost method worth trying.

After removing the stains by either of the methods described above, you will need to add a sequestrant to keep the metals in suspension and prevent them from redepositing as stains. Sequestrants slowly break down in the pool, so you need to add more regularly to maintain the correct level. Sequestrants based on HEDP, phosphonic acid, or phosphonic acid derivatives are the most effective. ProTeam's Metal Magic and Jack's Magic The Pink Stuff (regular), The Blue Stuff (fresh plaster), and The Purple Stuff (salt) are some of the top sequestrants. You can also find many other brands with similar active ingredients, some of which are noticeably less expensive.

 

[DesertGators]

I did try tri-chlor, but I just rubbed some on...will have to try holding it there. So far, no difference.

The stains are pretty widespread throughout the pool. We drained/filled in spring, and used what Leslie's recommended...stain and scale, cya, and some shock as I recall. We did not use anything for algae, but I don't know what may be in the town water supply.

I will try the vitamin C and post back. Thanks for taking the time to point me in the right direction!

 

[duraleigh]

read "The ABC's of Pool Water Chemistry" up in Pool School. From your last post, you seem to have some basic misunderstandings of what you need to know to maintain your pool.