What are these stains?

[Texaspoolmariposa]

Bought a house with a pool and it has these stains on the bottom near the shallow end. When we bought the house (two months ago) and had a couple pool companies out to do some work they said it was from the plants/ fertilizer possibly used in the yard. But I was hoping someone here could help confirm. Also how do I get rid of them?

 

[Texas Splash]

Looks like organic staining to me. You can test as follows:
1 - Rub a chlorine tablet/puck on the area. Don't just leave it there though. If it improves, it's organic (i.e. algae) and you'll need to increase the chlorine level and brush often.
2 - Rub the stain with a Vitamin C tablet. You can place several in a think sock or nylon. If it works, it's iron.

If any of those made the stain worse, it could be copper. Just let us know.

 

[Texaspoolmariposa]

I tried both of those this morning and neither made a difference.

 

[JamesW]

Hard to tell. Algae, scale, iron copper etc.

What are the chemistry readings?

 

[Texaspoolmariposa]

Hard to tell. Algae, scale, iron copper etc.

What are the chemistry readings?

I’m working on getting the calcium hardness and cya up

 

[Texas Splash]

Your CH is on the low end, so I'm assuming we can rule-out scale unless there was a major water exchage recently. Since the puck and Vitamin C tabs did nothing, you might try a little dry acid in a sock if you have some. That can confirm copper. If that doens't work, you may need to try a product like Magic Stain ID Kit. Surprised the chlorine tab didn't do anything. Just seems like an old organic stain to me. You have me curious as well now.

 

[Texaspoolmariposa]

Your CH is on the low end, so I'm assuming we can rule-out scale unless there was a major water exchage recently. Since the puck and Vitamin C tabs did nothing, you might try a little dry acid in a sock if you have some. That can confirm copper. If that doens't work, you may need to try a product like Magic Stain ID Kit. Surprised the chlorine tab didn't do anything. Just seems like an old organic stain to me. You have me curious as well now.

We did drain it when we moved in because the cya was over 200

 

[Texas Splash]

We did drain it when we moved in because the cya was over 200

I suppose it's possible that you are seeing residual impact from a high CH. If the prevous owners let the pH and/or TA get out of hand, it might have contributed to scaling. Do you see any confirmed scale anywhere else (i.e. waterline)?

 

[Texaspoolmariposa]

I suppose it's possible that you are seeing residual impact from a high CH. If the prevous owners let the pH and/or TA get out of hand, it might have contributed to scaling. Do you see any confirmed scale anywhere else (i.e. waterline)?

We have build up at the waterline/tile.

I don’t think the previous owners did anything to maintain the pool. They left tabs in the floater and that is it. When we had the inspection the filter pressure was at 30.

 

[Texaspoolmariposa]

When I try to scratch at the stain with my fingernail it does nothing. Would scale come off if I did that?

 

[JamesW]

It might be etching and pitting from low CSI. The surface is compromised in any case. Probably a mix of issues from bad chemistry.

You're probably going to need a replaster to get a really good surface.

Brush daily and maintain good chemistry to make the best of what you have.