Mega problems-what to fix first?

[Rainee]

I've just taken over the care of a four year old fiberglass pool (9000 gallons) with a SWG. Its water is always clear, but it has had black algae spots for a month and now I'm seeing possible mustard algae spots too. I read all the pool school articles, then bought a DPD kit and tested the water. The results are so bad that I don't know where to begin. For starters, there is zero CYA. My husband (the previous caretaker) tells me that he has NEVER added any. There is also zero FC even though he set the SWG at 100% output three weeks ago. He was running the pump just four hours a day. Starting yesterday, I set it to run for 8 hours daily. I also noticed the SWG "inspect cell" indicator light was flashing. Last night I removed the cell, scraped off the deposits and reinstalled it. I reset the indicator light and this morning it is not flashing. If the cell is okay (hopefully) what is my next step? The salt level is too high (3900 ppm) but should I add CYA before adressing the salt problem? Should I add bottled chlorine now or wait to see if the SWG can produce enough to kill the algae? Additionally, the pH and TA are high because of the hard water in our area. My husband was adding a pint of muriatic acid almost every week.

Rainee
Davis, California
9000 gallon IG fiberglass pool with SWG
1 HP pump, cart filter, 100 gpm flow rate

pH: 8.2
TA: 250 (pool store says our hard water causes this)
FC: 0
TC: Less than .5
CH: 120
CYA: 0
Salt: 3900

 

[reebok]

you need to get the ph down right away. use muriatic acid and www.thepoolcalculator.com to figure out how much to add to get to 7.4 or so.
you also need to get CYA in there asap, shoot for 80ppm, use www.thepoolcalculator.com again
you should turn down production on the cell and start using bleach or liquid chlorine to shock per the instructions in pool school.

pool-school/shocking_your_pool
pool-school/pool_calculator
pool-school/water_balance_saltwater_generator

 

[dravenone]

The SWG will not be able to keep up with the algae, it needs your help by adding bleach or liquid chlorine. I blieve you need to go in the folowing order unless a sight expert says otherwise.

1) Lower your PH keep it between 7.5 and 7.8 to prevent scale on thew SWG
2) add bleach to shock levels, check every few hours and add as needed to maintain shock levels
3) add CYA, the pool calc can tell you how much, add maybe 80% of the amount the pool calc tells you then test after several days. If you go over on CYA you need to drain and fill to brin it down
4) I wouldn't worry about salt unless the SWG is stating the level is too high.

 

[Rainee]

Thanks reebok and dravenone-this is all new to me and I really appreciate your advice! I'll add muriatic acid, CYA and superchlorinate with liquid ASAP. At what level should I set the SWG while doing this? And the black algae spots...should I try to brush them off while correcting the water balance?

Rainee

 

[reebok]

you really need a FAS-DPD test, not DPD, but you can work with that if you have to.
I suppose set the cell for 50% or so. you're just killing it faster by running it at a higher setting, and the thing has been in poor water chemistry already (no offense, we've all been there).
definitely brush them off while shocking. what cured my black algae spots was rubbing a trichlor puck directly on them for a couple days. you may not have any if you have an swg, maybe you can ask a friend or see if the superchlorination takes care of it, but I personally wouldn't count on it. other opinions may vary.

 

[dravenone]

I'm with reebok. Black algae is tough stuff, but I have a plaster pool. It creates a protective layer on the outside so it "protects" itself from chlorine. For plaster a lot of brushing is required, not sure what you need to do for fiberglass.