Patches spots on pool floor

[klpugh]

Hey all!

Im new to this. We just bought our house in January. Everything was good until around March when we had some pump issues. The pool sat for 2 weeks till the part for the pump was replaced. After we got it back up and running, we noticed these patchey spots on some areas of the pool floor. It seems to be getting worse with time. (See pictures)

We have tried:
-Descaling
-Tried use a lemon and lime to see if that would do anything to see if we needed stain remover. Nothing happened. Acid from that didn't even make it budge.
-tried black algae based on Leslie Guy's recommendation. Did this treatment with some black algae remover with a wire brush. Nothing happened. Shocked with 4lbs of shock for 3 days in a row while using the wire brush. Nothing.


Any advice? Should I try the stain remover?

 

[pooldv]

Welcome to TFP!

Try rubbing a trichlor puck on it.

 

[klpugh]

I tried that as well. I forgot about that until you mentioned it. It didn't do anything. I even tried in multiple areas just to double check.

 

[pooldv]

Is it rough to the touch?
If no, rubbing a vit C tablet there and leave it for 30 min to an hour if necessary.

 

[klpugh]

No, it's not rough to touch. I will try the Vit C and get back with you.

 

[klpugh]

The Vit C didn't work.

 

[pooldv]

Ok, now on to more complicated things, see if this helps, Diagnosing Pool Plaster Problems

 

[klpugh]

This talks about NEW plaster but I'm not 100% when it was plastered/replastered. I know it hasn't been in the past 3-4 years. It definitely sounds like one of the first 2 listed. We didn't have this problem when we bought the house, which makes me question if this has been in the process or sprung all of a sudden.

Most of these options talk about acid washing. What does this consist of?

Thanks for the help!

 

[pooldv]

An acid wash is very aggressive and will shorten the life of the plaster. It involves draining the pool and washing/brushing the plaster with muriatic acid. It removes a layer of plaster and exposes new plaster. You could do a no drain acid bath. Or an AA treatment, Ascorbic Treatment to rid Pool of metal stains

So, these stains just showed up? Is there any source of copper? Algaecide, mineral sanitizer system, a heater being corroded by low PH below 7.0 are the typical copper sources. If it is copper then ascorbic acid will lift it. How long did you leave the Vit C on the stain? You can try letting a Vit C tablet sit there and dissolve for a few hours to see what heppens.

 

[klpugh]

It did randomly show up. I thought it might have been due to the pool just sitting for 2 weeks, but now that you mention the heater I think that may be it. We ran the heater with the spa once since we've bought the house and it was right after we got the pump back up and and running after 2 weeks. I test the water regularly, but the ph is always within range. There has only been one occasion where it was higher than it was suppose to be and that was fixed rather quickly.

I left the Vit C on a spot for about 30-45 mins. I will try a longer period of time tomorrow and see if that helps. The heater/metal stains would make sense because the patches are all around the area where the water feature pushes the water from the spa to the pool. Will post after second round of vitamin C.

 

[klpugh]

I did the vitamin C again, except I left it for about 15 minutes this time. Came back after 15 minutes to a completely dissolved tablet and black spots! (See picture)

It kind of looks like the area around the black spots are cleared a bit. Downside is now I have black spots that won't come off with brushing or wire brushing.

 

[pooldv]

Black spots further confirms that the stains are copper.

OnBalance, plaster expert, say this about black stains from copper
The stain is probaby copper, which turned black (copper oxide) on the surface after you added the chlorine shock. I suggest purchasing some "potassium alum" granular (two or three pounds) and sprinkle it over the staining. It should remove the black stains very quickly. Vacuum to waste any residue on bottom after that, or clean filter a day later.
in this post, Staining caused by chlorine shock.

Or do the AA treatment linked in this article, Pool School - Metals in the Water and Metal Stains

 

[klpugh]

Thank you so much for your help! On a positive note, 2 hours later and the black spots are pretty much gone. I guess the chlorine is washing it off. Also, the stains in that area have seemed to lighten up a good bit, if not completely gone. I will try the AA treatment. Is a sequestering agent like metal free liquid that you pour in your pool?

I am definitely considering switching to the TFP ways because I've only been trying to figure out what this stain is for the past 2 months!

 

[pooldv]

Yes, a sequestrant is a liquid that you pour into the pool. Like Metal Magic or Jack's magic. I think an AA treatment is a good next step. I think switching to TFPC is a great idea!