Green Water - mustard algae

[SAP_Pete]

Thanks !
Water is clearer, but is still a little greenish. Algae on the walls, although less (brushing several times a day).

Last night:
FC 17
This morning:
FC 13
(all other readings stable)

I hit it with another gallon of 8.6% bleach, so it should get me well above 20. I'll keep checking throughout the day.
My understanding is to keep it a shock level until the overnight FC loss is negligible ?

Any thoughts on the calcium hardness ? Two pool stores I went to didn't have any calcium chloride, so I ordered some Driveway Heat online; should get here next week. Lost 20 tiles around the spa overflow so far, and the grout all around the waterline doesn't look so good.

[Watermom]

I would just use bleach for now and once the water is cleared up, then you can worry about CH.

You want to keep at shock level (per Best Guess Chlorine Chart in my signature) until three conditions are met:
1. You lose no more than 1ppm of chlorine overnight
2. You have no more than 0.5 CC
3. Your water is clear

At that point, we recommend keeping the chlorine high for one additional day. Then, you can let it drift down and keep it in range between the min and max listed in the chart. Run your pump 24/7 while you are trying to clear this up. What kind of filter do you have, by the way?

One last thing. Don't trust pH readings taken while the chlorine is higher than 15. (If you didn't have a Taylor K2006, I would say don't trust pH readings when the chlorine was over 5.)

[SAP_Pete]

Thanks, I'll try and keep the chlorine up for a while. I have a cartridge filter with 4 cartridges, cleaned it yesterday. I just got a K2006 this week, so that's where I got my numbers. The pool stores around here don't have any decent test kits (but that's normal I guess).

[Watermom]

Sounds like a plan. Let us know how it is going!

[SAP_Pete]

Been on vacation and incommunicado for a while.

Pool has cleared up, but otherwise the numbers are much of the same.
Losing 4-5 ppm FC over night
CYA is 150ish, although 90% of the water had been changed, with no trichlor / cya added since. 2006K onlye goes to 100, and it's a bit higher. The test strips I bought before getting the 2006K show about the same.

CH was still at 140. Added 4 pounds of calcium chloride (DrivewayHeat) to get started on this.

[PoolDoc]

If you haven't yet, read the Best Guess page, linked in my signature block. Very relevant to your situation.

Maintaining correct pH and reasonable calcium levels IS important with a concrete & plaster pool.

Mustard algae takes HIGH chlorine (per Best Guess) + mechanical cleaning (brushing) + time. Often, you can't completely eradicate it, only keep it under control.

[PoolDoc]

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