Green Water - mustard algae

Hi Guys,
good to be here, and I read a lot already. Here's my current dilemma:

Water kept turning green, with greenish / yellowish algae clinging to the walls. The wife kept dumping trichlor powder, which didn't seem to do much, so I started reading up on stuff here. Got a CYA test strip (all they had at the pool store), and CYA was through the roof.

1. Emptied 90% of the pool water (loaner pump had to go back at this point)
2. Refilled with tap water
3. Tried to balance with bleach, but water turned green pretty quickly
4. It's pretty hot here (daytime 115 degrees this week), so that doesn't help

Got my Taylor K-2006 yesterday, and tested:

FC 17
CC 1
pH 7.8
TA 160
CH 140
CYA 70

Added 1/2 gal acid last night, and checked this morning:

FC 10
CC 0
pH 7.2
TA 140
CH 125 (used the 25 parts per drop this time)

The pool is still green. I can still see the floor at the deep end (6 feet). Water circulates through the pool cleaner - pump - filter - spa - overflows back into pool.

I've used some leftover trichlor powder and then regular bleach.
My question: Do I need to hit it harder / for a longer time with bleach ? Should the pool clear up if the algea is truly dead, or does green mean there is still algea alive ?

Water is still green, adding 1-2 gallons of bleach per day to keep FC up, and keeping pH in check.

I know CC shouldn't be my main concern, but it's a plaster pool, and I had recently some tiles fall off. I read some posts that contend that CH doesn't really matter, but I wonder if it's related. There is no harm in trying to bring up CH at this time, right ?

Also just noticed that I wrote CC in my first post twice. The 140 / 125 number obviously is CH, not CC. Tested CH again today with the 10 ppm / drop, and came to 140 again.

What are your current readings?

I edited your post above and changed the CC to CH for you.

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.

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.)

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).

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

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.

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.

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