Identify these stains please

[aggiejet]

Howdy,

This is an ongoing issue, which I think is getting worse, but my wife disagrees. She does most of the vacuuming. There are several areas around the pool where this occurs, mostly in the deep end. This are brownish stains.

This is the second year of TFP. I replaced about half of the water last year due to really high CYA after properly testing the water. Also, I'm relatively sure a lot of copper got put in the pool early last season by the "pool guys" (before we fired them) when they cleared up the green water.

I maintain the FC at 4ppm, Ph about 7.5ish (add about a pint of acid every day.
TA=100 CH 270 CYA 40

Brushing with stainless steel doesn't help.

Thanks

 

[Texas Splash]

Some ways to troubleshoot an unknown stain are as follows:
a. If it's dark in color and/or rough, it may be scale from excess calcium - possibly with something embedded in it. Excess calcium requires scrubbing and/or possible acid treatment to reduce the excess scale (reference the CSI index)
b. Try vitamin C on it. Regular tablets crushed in a sock will do. If it lifts the stain it was probably iron (i.e. from well water). If it made the stain darker, it could be copper (i.e. from algaecides) in which case try some dry acid on the same area.
c. Finally, try a tri-chlor puck on the area to see if it's organic. If that works, then an increased FC level may help reduce the overall appearance of the stain.
d. There are also over-the-counter methods to ID a stain (i.e. Jack’s Magic Stain ID Kit – about $15) that can be used to help identify the cause of a stain.

 

[aggiejet]

Here's a pic of a Trichlor puck next to an area I put about 10 vitamin C tablets on. Vitamin C area made the area turn black. So, copper stains? What is dry acid?

 

[Texas Splash]

It does indeed look like copper since it made the stains darker. You could try some dry acid if you have any. If the stains are currently growing or getting worse, you should get some sequestrant in the water right away. Sequestrant will bind to the metals in the water and stop them from forming more stains. It may also remove some of the existing stains. Another thing to do right away is to lower the PH down to between 7.2 and 7.4, which will also help slow down or stop any new staining.

ProTeam's Metal Magic and Jack's Magic the Pink Stuff (regular), the Blue Stuff (fresh plaster), and the Purple Stuff (SWG) are some of the top sequestrants. Many owners have had good luck with those. You can also find many other brands with similar products, some of which are noticeably less expensive. Sequestrants based on HEDP, phosphonic acid, or phosphonic acid derivatives are the most effective.

So aside from those interim measures, copper stains can often lead to a drain and manual acid wash.

 

[pooldv]

+1 to add a sequestrant and then drain half the pool and refill to dilute the copper to prevent more staining. Copper stains are the worst. Sometimes impossible to remove. Dry acid, sodium bisulfate, in a sock or muriatic acid in a spray bottle and a brush might lift the stains.

 

[aggiejet]

Well the plaster is about 14 years old and is mostly gone I believe. So it's probably about time for a drain and replaster anyway. In the meantime, I guess the water is safe to swim in.

In the meantime, what is dry acid? It looks like that spot is clearing up after I put the chlorine puck in that area. So, I thought I might try a regime of acid and chlorine pucks.

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+1 to add a sequestrant and then drain half the pool and refill to dilute the copper to prevent more staining. Copper stains are the worst. Sometimes impossible to remove. Dry acid, sodium bisulfate, in a sock or muriatic acid in a spray bottle and a brush might lift the stains.

I drained half the water last year after I figured out that I probably had copper in there from algaecide and my CYA was really high. That's what I can't quite figure out. Where is the copper coming from?

 

[Texas Splash]

In the meantime, what is dry acid? It looks like that spot is clearing up after I put the chlorine puck in that area. So, I thought I might try a regime of acid and chlorine pucks.

Muriatic acid is hydrochloric acid, typically used for prep work, concrete, and pools. Dry acid is sulfuric acid and adds sulfates to the water which can become problematic with time. It is also usually more expensive. Sulfuric acid is usually marketed as a safer alternative (no fumes) but possess much greater risk if it comes in contact with the body. The reaction of the puck might just be temporary or a minor change. Pucks usually have better success on organic stains. But the reaction to those vitamin c tabs indicates copper. But hey, if something seems to be working, keep working at it. Let us know how it turns out.

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As for the source of copper ... well.... perhaps even with the partial drain there was so much before it just helped. I don't see any copper items in your equipment, so it must be something chemically from before.

 

[pooldv]

The most common sources of copper are:
Algaecide
Clorox pucks and products labeled "blue"
Copper pipes and heaters exposed to low pH, 7.0 and lower for a while
Mineral sanitizer systems