Help....cloudy pool with stains and algae
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Fiberglass seems to be especially sensitive to iron stains. Are you on well water? Do you have a water softener?
Otherwise, your chemistry looks very good. Don't worry too much about the calcium right now -- it's not critical on an FG pool. But, when you get a chance, you might want to watch the Taylor calcium video - Taylor-K2006-Videos-on-YouTube
Using the polyquat (www.poolsolutions.com/polyquat.html) while you remove stains, allows you to operate with lower chlorine, without risking algae. You'll need both polyquat and HEDP to clear up the stains. But first, we need to figure out how the iron is getting into your pool.
Don't worry about your CYA -- it's fine!
If you want to do so, you can go ahead and treat your pool with borax -- maintaining a 60 ppm borate will make your pool algae 'resistant'. For a 20K pool, you'll need to add about 19 boxes of borax + 12 gallons of muriatic acid. That's over $100 . . . but the borax will remain permanently, except for what's lost by splashout or backwashing. If you *do* decide to add borax, add acid FIRST and then add the borax. That way your pH will stay low, which will help prevent stains. Actually, if you add 1/2 of the acid at a time, it will likely 'lift' the iron off the pool. Do *NOT* leave it low; add 1/3 of the borax, and then add more 1 box at a time til your pH reaches 7.4.
In fact, you can do it all at once:
1. Let your chlorine drop to below 5 ppm and backwash your filter completely.
2. Add 1 full quart of 60% polyquat.
3. Add a dose of HEDP (dose depends on which product you buy -- concentrations vary)
4. Add 1/2 of your muriatic acid.
5. Brush the pool and wait 2 hours.
6. Add 1/4 of the borax.
7. Wait 12-24 hours.
8. Add borax till pH reaches 7.4
9. Add 2/3 of the remaining acid.
10. Add 1/3 of the remaining borax
11. Brush again.
12a. If the pool is stain-free, continue adding borax till you reach 7.4. --OR--
12b. If some stains remain, wait 12-24 hours before adding borax.
13. Once you have reached 7.4, add 1 box of borax every 24 hours till your pH reaches 7.8 - 8.0
14. At that point, add more acid, till you get to 7.4, before adding more borax.
15. Shoot for a final pH around 7.6 - 7.8
16. During this period, maintain chlorine levels of 1 - 3 ppm, but add chlorine ONLY in small doses via the skimmer AND add 1/2 dose of polyquat every 2 - 3 days.
17. Once all the borax has been added, and the pH is 7.6 - 7.8, your stains will (hopefully) be gone. However, it is very IMPORTANT for you to understand that most of the iron is STILL in the water; you've just moved it from the walls, to the pool water.
18. Using chlorine added in SMALL doses via the skimmer (tabs?), gradually raise your chlorine levels to 10 ppm
19. If you have not had to backwash before, do so at this point regardless of pressure.
IMPORTANT NOTES:
(a) read the muriatic acid page, in my signature, before handling acid.
(b) do NOT dump the borax into the pool; it will clump and can remain for days.
(c) DO add the borax slowly to the skimmer, while the pump is on, being careful NOT to choke the skimmer.
(d) your filter needs to be functioning WELL for this process to work. Buy some DE powder to test it. Add a coffee can full to the skimmer. If no DE shoots out into the pool, your sand filter is working well. However, if you add DE to the skimmer, once you start the process above, the DE will help collect the iron and remove it from the pool. A good dose would be 1 - 2 coffee cans full for a 24" (300#) sand filter. You'll need to replace it after each backwash.
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