Is my CYA Test good if it was cloudy?

[JoeSelf]

I've been bringing my CYA down from 150+ this year. Did a half drain and refill. Started at 90. 2 weeks ago around 80. Tested yesterday at 2:00 pm and got 70. But this time it was cloudy, no shadows. Is the test still good? It rained the past two nights before.

Here are my numbers:

FC 8.5
CC 0.5 up yesterday
PH 7.8 creeping up, has held @ 7.5 for long time.
TA 100 down from 110
CH 125 steady
CYA 70
Temp 78

Still going by CYA 80 numbers for bleach.

Also: I have not had to backwash for filter pressure in about 3 weeks. I just got the pressure gauge from TFT and it was only reading 13 PSI (previous had 14) now 14 PSI. Is this normal to go so long with out having to backwash. The water is crystal clear and when I turn on the light at night I don't see much of anything floating in the water like in the past. Thank you all for such a great site.

 

[jblizzle]

Welcome to TFP!!!

The lighting is pretty important with the CYA test, so I am not sure how accurate the 70ppm reading was if it was cloudy out ... I think it might read a little higher than if it was sunny out.

If you keep algae out of the pool and have an oversized filter (yours is a good size), many members can go the entire season without backwashing. Just wait until the pressure rises 20-25% above the clean pressure (about 16psi for you) and then backwash.

 

[JoeSelf]

OK, so I finally had a chance to run the CYA test Sunday midday (4:20 pm?) was running around earlier. I got a reading of 60-70. I also ran the test on Wednesday after work around 6pm. It was very sunny and w/ back to sun I got 70 also. The side of the house is a light yellow and moved closer to the wall to see if the sunlight reflecting off the siding would affect the reading and it did not.

So is the position of the sun high in the sky and the ambient light critical to the test?

 

[Smykowski]

I'm not sure position of the sun is important per se, Taylor just says bright, indirect sunlight.

 

[Patrick_B]

I'm not sure position of the sun is important per se, Taylor just says bright, indirect sunlight.

Bright and indirect.

 

[JoeSelf]

Cool, thanks guys.