Possible Mustard Algae.....

[crumtastic]

I'm helping a friend get his pool balanced and teaching him how to properly maintain it. He recently installed a SWG and now has yellow stuff covering most of the floor of the pool. I ran a full test on it last night and got him started shocking. Most of the "stuff" on the bottom comes up when brushed, or vac'd, but there is still quite a bit that we can't seem to scrub off.

36,000gal plaster pool shaded most of the day
Sand filter
2hp pump (new A.O. Smith motor this season)
New SWG (50,000 gallon model, can't remember the brand off hand)

Initial results......
FC 0
CC .5
PH 7.8
TA 210!!!! (got him started adding acid to start bringing that down)
CH 310 (been using Cal-Hypo before SWG)
CYA 0!!! (Tried to get some from Walmart when we were getting bleach but they were out. Trying to get some today to get him
25-30)

We dosed to a shock level of 13 (based on the calculator) and gave it an hour. After an hour we tested again and got FC 13 and CC .5. Dosed up to 20 (I think he miss calculated, I had left by then) for the night and was at 16 this morning, but still CC at .5. Although it may have been a larger drop, can't remember if I told him to turn off the SWG (which is in boost mode) for the OCLT.

I'm starting to wonder if it actually is algae....... I figured the CCs would jump quite a bit overnight. The water is only cloudy after we brush the "stuff" off the bottom. I'm going over at lunch to check it and dose if necessary and will take a picture and post it along with the test results.

Thanks for you help in advance. I would have been lost with my pool if it weren't for you guys!!!!

 

[Bama Rambler]

If he lost 4 ppm FC overnight then it's most probably algae. Keep it at shock level till he passes the OCLT. You can be shocking algae and never have any CC's.

 

[crumtastic]

Thanks Bama!!!
I thought I had read that somewhere but couldn't find it.... We'll keep shocking and hope that it starts coming of better. I'll still post pics and results after lunch to keep track.

Thanks!!!

 

[crumtastic]

So I forgot to get a pic of the pool... , but here are the numbers:

FC 4
CC .5

He kinda freaked out when I told him it was 4, but I told him that the sun was doing most of that damage, since there's no CYA.
He found some CYA and is going to dose up to 25-30 after work and bring the FC back up, which will probably be back to 4 by then. When I left it was at 18 and the pool will be in the shade soon so hopefully it won't drop too much.

The floor was mostly clean when I got there and I was able to easily brush off most of the rest. It's now grey instead of yellow and I could see the bottom of the deep end, 10ft, before I started brushing everything down to the main drain.

We should start seeing more results tomorrow with the CYA and it should start clearing up. He has a pool party planned for Sunday so we're trying to get it cleared up for that, but I didn't make any promises....

 

[RobbieH]

Don't forget, after you are done shocking you need to get that CYA up in the 70 range.

 

[crumtastic]

Great news!!!!
He passed the OCLT last night and CC is still at .5 or less. Going to keep at shock level today and add a little DE to the filter to help clear the water faster, hopefully it will be clear tomorrow and we can stop shocking. He put in enough CYA to get to around 30, and will dose up to ~70 once we're done shocking. Looks like the chances of swimming Sunday are getting better.

Thanks to everyone on this forum, and the fact that we caught it before it hit critical mass, I have converted another pool owner. He ordered his test kit and is taking control of his pool. Should be TFP from here on out.!!!!