Cloudy water, but none of the usual suspects?

[aharon]

Water has stayed cloudy enough through this years opening such that the bottom drain is a barely visible blob. It's clearer in the shallows. Water color is good, the translucency is like when you do a CYA test, the deeper the water column the more opaque it gets.
I cannot identify anything different about this year. Water chemistry seems ok, I have kept liquid chlorine between 9 and 20 to cover that base. CYA 50, pH 7.5m, CH 200, TA 80. I haven't added any substances to the pool. Superpump works as usual, visible water flow in the pool. As in previous years there is a tiny amount of DE coming through my filter grids, but my Nautilus robot traps it in its own fine filter grids, again, like other years. Can DE remain suspended in the water for weeks? It always seems to have fallen to the floor.
I've been at this for 3 weeks and cannot figure out what is causing the cloudiness. I'm wondering if I should resort to a flocculant but that seems like a terrible short-term band-aid. Anyone seen mystery cloudiness before? I'm really skeptical that it could be algae-related; I haven't done a SLAM, but I have also never ever seen algae that wasn't killed with normal chlorine levels and that wasn't captured by the filter. There is no algae on my surfaces.

 

[Kellyp]

Well you can rule out algae pretty definitively by doing an overnight chlorine loss test. I would start there to rule it out.

 

[Pool_Medic]

Cloudy says it’s not passing OCLT. Slam will get it sparkly clear.

 

[aharon]

I lost 0.5ppm of Chlorine in the last 24 hours, and it was very sunny here. CC is 0. This cloudiness is just not consistent with algae problems I've had before.
On the other hand, I just noticed something very unusual. There are a few water-skimming bugs of some kind skating on top of the pool. Every year they disappear even with low levels of chlorine, 2-3ppm. So you would say that my test kit is screwy, but I just used two test kits, the basic "yellow" one which can only indicate up to 5ppm and my FAS-DPD which is what shows me the current 8.5, and appears to accurately show me 20+ppm when I dump gallons of 12.5% liquid Cl.
Anyone ever seen bugs on a properly chlorinated pool before?

 

[Oly]

Losing only 0.5ppm FC in 24 hours in a 22k in ground pool in sunny PA at near peak season is impossible, my opinion only.
Try the Overnight Chlorine Loss Test, follow it in detail and let us know.
Why search for a rare cause of cloudy water before properly diagnosing for an algae bloom?

 

[aharon]

Try the Overnight Chlorine Loss Test, follow it in detail and let us know.
Why search for a rare cause of cloudy water before properly diagnosing for an algae bloom?

This is new behavior in my pool for the first time in the 11 seasons I've opened it. I thought I had a good handle on the interactions between various infestations of green and mustard algae and liquid chlorine and CYA. And organics that may have dropped in. But the pool is free of visible debris. And keeping my FC elevated is getting pricey. But you are right, no reason for me not to keep a track. This evening FC was still 8.5, I will check again in the AM.

 

[Deb04]

This evening FC was still 8.5, I will check again in the AM.

Remember there should be no sources of chlorine overnight. Any SWG turned off, no chlorine additions, no pucks.

 

[aharon]

The next day FC had dropped by 2.5 to 6ppm. So something is at work there. I haven’t added chlorine since. The cloudiness is decreasing slightly but not completely, even though the filter has reached the point where it will now go for weeks without an increase of pressure; I have never had cloudiness or any water condition that did not disappear at the same time the filter pressure dropped to normal and stayed there. And I still have water bugs that don’t seem to care about the chlorinated water. I will keep an eye on the Cl consumption. Very confusing.

 

[Oly]

Algae in pool water attracts water bugs. If your overnight FC dropped by 2.5ppm then prepare for the SLAM Process