cloudy darkish water

[fhorta]

I just don't understand the growth of algae if chlorine always @ 6 or more and cya not over 50, with pump circulating 6 to 7 hours. Its like your getting algae no matter what. Thanks, ill do the bucket test.

[Watermom]

Have you kept your chlorine at shock level for a period of time until the algae is dead? If not, then that is why you continue to have algae. With a CYA of 50ppm, your shock level will be about 15ppm to kill it.

But, do the bucket test first before shocking the pool.

[fhorta]

Sorry, been out for a while. I have not done the bucket test yet, but this is whta has happenned. I thre in some potassium peroxymonosulfate (fresh n clear) 3 lbs and water cleared within a day and a night. Stayed clear for about 3 days and now greenish again. All other values are same, chlorine at 6ppm. Anyway, I am being told that problem is sand filter cus it doesn't filter small microns and that instead of using diatomaceuous earth I need to use cellulose fiber, a de altenative because it filters smaller microns...any comments on this??

[PoolDoc]

Without getting into it, the ONLY reason for cellulose is as a replacement for DE in DE filters. You have a sand filter; we're using the DE primarily as a test. The cellulose can NOT be used for that purpose (and it's not all that good as a DE replacement, either!).

We would have told you not to use the monopersulfate . . . but the result you got is very surprising. MPS would have had NO effect on algae. I am completely puzzled by what could make your pool green, be cleared up by MPS, and then return to green. I'm going to see if Chem_Geek has any ideas.

Meanwhile, please take your kit and do a COMPLETE set of tests on your pool: FC, CC, pH, TA, CH, and CYA and report those.

Also, turn your pump on and leave it on.

Finally, when you need to backwash, please note the color of the backwash discharge.

Thanks,

[chem geek]

MPS is acidic so if the green, or at least some of it, is from metals then the green may have gone away when the pH dropped and then come back when the pH rose again.

If there is algae creating cloudiness, then just maintaining a normal FC/CYA level will not get rid of it because if the water is cloudy and if that is from algae then the algae is clumped enough that it can still grow inside the clumps faster than chlorine can kill it from the outside. That's why we shock the pool in this situation to raise and maintain a higher FC/CYA level to completely kill off the algae.

What I suggest you do is first lower the pH to at least 7.2 (but not below 7.0) and see if the green lightens at all. Then shock with chlorine to 20 ppm FC (assuming your CYA is really 50 ppm) and maintain that level which means adding chlorine multiple times during the day (or at least at morning and early evening if no one is around during the day). If it gets green again, that would be from the chlorine raising the pH. Don't worry about that. Just hold the high chlorine level and filter 24/7 (using both the skimmer and floor drain) to get rid of the cloudiness. Once you get to a clear green then you can deal with the metals.

Is your pool surface blue? If so, then you may have iron in the water (that's not uncommon in well water) since yellow+blue looks like green. Otherwise, green is usually from copper. That usually comes from use of a copper algaecide and is not usually in well water.

[PoolDoc]

MPS is acidic so if the green, or at least some of it, is from metals then the green may have gone away when the pH dropped and then come back when the pH rose again.

Ahh! I forgot that it was so acidic. It's been a LONG time since I messed with MPS.

Thanks, Chem_Geek.

[chem geek]

The equivalent amount of oxidizing power as 1 ppm FC when added as MPS (6.7 ounces weight per 10,000 gallons) has the same acid effect (after usage/consumption) as 2.5 ounces of full-strength Muriatic Acid (31.45% Hydrochloric Acid) per 10,000 gallons. It's actually somewhat more acidic for equivalent FC than Trichlor.