Pool cover makes water go hazy

[rlab]

Our pool has an opaque thermal foam pool cover (4mm sandwich of closed cell foam) rather than a translucent bubble cover. We keep the cover on 24 hours a day except when swimming (drought and water restrictions here).

I have found that if the pool doesn't get much use in a given week, the water gets a white haze to it. If I remove the cover for 24-48 hours then the haze goes away completely and water goes back to crystal clear. There is no change in FC or CC that I can detect.

What is going on here? This is not an issue I could find anywhere in TFP articles. Opaque covers seem uncommon, could it be something to do with blocking sunlight?

Params
FC 8.5
CC 0.5
PH 7.8
CYA 60
TA 60
CH 350

 

[Newdude]

Do you open it at all in between uses or just leave it covered the whole week? Does it smell funky for a minute or two when you open the cover ? It sounds like the pool needs to breathe more often. The CCs build up when covered and the UV from the sun can't burn them up. They'd probably be gone by the time you got to test them.

Try opening the cover for sunlight twice a week. An hour is probably plenty.

 

[rlab]

Covered except when swimming, so often that can be only an hour or 2 each day it's uncovered. But that doesn't seem to be enough, needs that good 24-48 hours of continuously uncovered to prevent or fix the hazy white.

Definite chloramine smell whenever the cover comes off. It makes sense that chloramines could be building up, but would that make the water hazy?

Nowhere in any TFP or other literature have I seen anything about pool covers making pool water go hazy.

 

[cowboycasey]

your right, mine has never gone hazy.. It does need to be taken off for about 6 to 12 hours a week to burn everything off.. I leave it off for the day, 1 day a week..

What do you keep your FC at? I keep mine at or above 7 and have no issues

 

[mknauss]

Check pH right at taking cover off. High pH can cause water to look duller.

 

[Prickly]

Maybe it is dust that comes off the cover when you remove it. Also, skimming doesn't really work while a cover is on so the haze could be from that.