Green to Turquoise but ~ Stable Chlorine

[nordwind]

I think I followed protocol by getting pH to 7.5 and TA to 120 before measuring zero Total Chlorine (despite using 3" tabs in parallel with the filter). CYA tested at 100, but the water was too green for that test to be meaningful.

The dealer tested CYA at 54. I've removed the chlorinating tabs and have been diluting steadily. It should be below 50 by now.

Shocking to 20 and repeatedly raising it back up above that level cleared the green in a few days, and the filter removed green residue.

The water remained blue-green, and I could only see 3 - 4 feet down into it. It is not sufficiently cloudy to discern any color when removed from the pool and viewed through a clear glass.

Another week of keeping CYA above 17, brushing, and vacuuming produced no color change, no filter pressure change or residue, and no change in the rate of consumption of Chlorine.

So I shocked to 30. That level held overnight and declined only slightly the next day. (The pool is covered.)

Is this haze something non-organic? The pool has always been refilled from the house supply, which is well water run through a water conditioner. That was also the case before I bought the place and it had crystal clear water.

 

[JasonLion]

Welcome to TFP!

I would guess that there is some issue with your filter. If you have a FAS-DPD chlorine test you can check overnight FC loss to be sure if there is any algae still growing or not. Once the algae is dead it will typically take several days to a week for the filter to clear the water, with a visible improvement each day.

Check to be sure you have the main valve in filter position (if you have a main valve). If you haven't backwashed the filter in a while you should probably do that now. When you do, check to see how dirty it was. There is usually a sight glass and you can watch to see how long the water in the sight glass stays cloudy while backwashing. See if the pressure gauge is still working. It should read zero when the system is off and at least a couple of pounds of pressure when the system is on.

It is also possible that the sand has become channelized, letting debris go right through. One way to check for that is to tie a nylon stocking to a return jet and see if anything collects in it.

 

[nordwind]

Thanks for the advice.

I think that it was indeed the filtration. It has cleared VERY slowly. It is clear now, after almost a month. Marginal filter performance and/or tiny algae.

I have read that turquoise coloration remaining after clearing green algae can be difficult. But then I haven't been able to exonerate the filter yet because of access limitations.

So now I'm moving on to other parameters, and aerating with a small fountain driven by a return. (I wasn't able to get the step jets to aerate reliably.) Is it possible to take the bull by the horns and aerate quickly? Like maybe a shop air compressor feeding a number of suitable airstones. Or is this a chemical process that won't proceed quickly, or maybe that air would leave petroleum residue in the water??

Thanks again.