New pool for in-laws. Need to identify and clear up algae

[rpoldervaart]

Hi everyone,

My in-laws just bought a house here in Houston with a pool. I have a SWG pool myself, but don't have much experience with traditional pools.

The pool definitely looks like it has some black algae, black clumps with crusty cover, turns green if scraped. They also have a yellow tint on the floor and walls. The yellow is not a build up or clump, but just a tint. I can rub it off the wall with my finger. Is this just pollen, even on the walls? Or is this a type of algae?

Given the cya level 100, should I recommend a partial drain? Is 50-60 a good target for CYA for traditional pool? I know it will be easier to shock the pool if I lower the CYA.

If people only use tablets, do they always have to periodically drain water to reduce the CYA? Or, does backflushing typically waste enough water to keep CYA in check?

Numbers are:
16,000 gallons
FC 8.5
CC .5
Ph 7.5
TA 90
CH 450
CYA 100

Thanks,
Robert

 

[Abigail K]

With CYA "100", the first thing I'd advise is to do the dilution CYA test to get a ballpark on the actual CYA. See extended test kit directions, post #8, step 9.

The description definitely sounds like black algae.
If your in-laws have a blue liner, the yellow tint is probably algae.

With CYA "100", a partial drain is definitely recommended unless there are water restrictions. Target CYA depends on the location.

If people are using tablets exclusively, then at a certain point they would have to drain water, backflushing alone does not keep CYA in check.

How are you getting those test results?

 

[rpoldervaart]

Thanks Abigail,

Thanks for the reply.

I should have said the pool is plaster. I'm also in Houston where it's currently 90-95 air and water temp.

I'm going over there now to talk to him about replacing about 50% of the water. I'll try step 9 of the extended test kit directions #8 when I get there. The only difference I've done is I've always faced the sun instead of having my back to the sun.

I have a PS233 test kit from Ben (PoolSolutions) years ago, similar to the TF-100, and have bought the replacement chemicals from someone (Dave, I think) on this forum (tftestkits.net).

Robert