To drain or not to drain pool with high CYA?

Scrape the spots with your fingernail, then smear the crud on a white 3x5 card (or similar) -- black algae smears dark green.

If it *is* black algae, I'd recommend pressure washing first, and then pouring plain household bleach on all spots. Wait till late evening, and then pour bleach liberally over all spots

Be careful, when pressure washing, to NOT strip the plaster. Old or soft plaster can't take a lot of pressure. Also, try to refill ASAP -- being dry is BAD for plaster, especially old plaster. You're in California -- lots of sun & dry air. You may want to set up a couple of sprinklers or misters on a timer to keep the pool walls damp.

Thanks Ben. I really don't want to pressure wash it because it is too old, (1986). I know it needs re-plastering but want to try and get a couple more years out of it. I did what you said and it is definitely black algae.

Would it hurt the plaster to pour bleach directly on the spots? I heard that you can also rub a 3" Trichlor puck on them. I am going to try and work on them now and then start the refill. Should I be pouring bleach in at nighttime when refilling, even though the pump is not running?

Thanks again.

I'd use bleach, not trichlor. Trichlor is acidic, and if you get enough on the spot, will damage the plaster. (Doing in a pool that's full is much less risky.)

Bleach will not damage the plaster, as long as it has no organic binders or materials present. With an old pool, that shouldn't be a problem. I'm not sure if acrylics or latex binders are being used in new plaster.

BUT if your plaster is as old and deteriorated as your concern implies, do NOT let it dry out.

Well, I did all this before your reply since I am in the process of refilling and trying to move fast. I used a trichlor puck and it wasn't too bad...yes, it left some marks but there are lots of marks already. I was contemplating getting it re-plastered while it was almost empty but can't afford it right now so trying to get a couple more years out of it.

It is dried out because it took so long to drain...I probably should have rented a pump like I did last time and drained and refilled it fast. What do you think will happen now that it is dry and I am refilling? This pool is killing me.

Thanks.

Quote:

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Originally Posted by stevemac213

What do you think will happen now that it is dry and I am refilling?

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Dunno. Letting the plaster dry doesn't always cause problems. All you can do is cross your fingers and hope for the best.

I certainly will....and pray as well.

Should I put in a gallon of chlorine tonight, even though the pump is not running or should I wait till it is full to shock it?

Thanks Ben for your timely replies.