Stain Removal Advice

[WetSteve]

Brand new pool, only eight weeks since it's been filled and since day 1, this stain has been getting worse and is around the entire pool (see photo). Nothing added to the water (tap water to fill), just a little muriatic acid twice. Pool builder doesn't know what caused it.

The pool builder says they need to add acid to the water and over a four day period, brush the pool twice a day. The heater can by bypassed, but I'm guessing since this is a four day process, a lot of acid will be added.
Will this affect the plaster at all, as in make it thinner or damage it? Can any of the valves or pumps be damaged? I'm concerned that this will work but the pool could be damaged long term, and so I'll need a longer warranty from them?

Thanks for any input.

- - - Update
View attachment 67364

 

[YippeeSkippy]

Huh? You've not added any sanitizer for 8 weeks??

'splain Lucy? <said in Ricky Ricardo voce>

Maddie

 

[WetSteve]

Huh? You've not added any sanitizer for 8 weeks??

'splain Lucy? <said in Ricky Ricardo voce>

Maddie

Well yeah, sorry, I do use sanitizer. I didn't mention that cause it's a given, dontcha know <said in North Dakota voice LOL>

I use the 2" tablets and adjust based on pool readings; pool is absolutely clear (unfortunate cause the stains are more visible)

 

[YippeeSkippy]

Well yeah, sorry, I do use sanitizer. I didn't mention that cause it's a given, dontcha know <said in North Dakota voice LOL>

I use the 2" tablets and adjust based on pool readings; pool is absolutely clear (unfortunate cause the stains are more visible)

LOL, actually, that's not a given sometimes around here.

Its hard to see from my side, but is it only under the tile, or is it on front of the step too?

Do you have any of that tile left over, sitting around? I'm wondering if it might be coming off the blue tile. Odd, I know, but if you could somehow test that out we could rule it out. Perhaps exposing it to some MA and LC (not together, of course!) and see if it bleeds a bit?

Maddie