FC levels with high CYA

[Ms1780]

First of all thank you for this site. I put an above ground pool in last spring that holds 17,000 gallons. Last season I used ez pool and found it to work well but it was very expensive. This year I switched to 3" trichlor tablets and granular dichlor for the occasional shock. When it got really hot here, near 100 degrees my water got cloudy and I couldn't get it to clear up. I shocked it a couple times not realizing that I was only making my root problem worse. My CYA levels were up around 90! I used drop out and drained 1/3 of my water and vacuumed and refilled. My CYA levels are now around 65.

I am now switching to liquid bleach to prevent my CYA levels from going up again. So my question is with cya levels at 65 should keep my FC higher than 4? I really don't want to replace more water if I can avoid it.

On a side note the local pool store tried to tell me cya levels make no difference.

I am also curious about what to do after a big rain or a pool party since this says you don't need to shock. Do you just test the water and bring FC back to 4 after the rain?

Thanks in advance!

Mike

 

[jblizzle]

Where are you getting the FC level of 4? According to PoolMath and the FC/CYA chart in pool school, with a CYA of 65, which you should round up to 70, the minimum FC you need to maintain is 5ppm. Which means that daily you should be targeting 8-9ppm so it does not drop below 5ppm.

Before heavy use, bump the FC up a little extra and test after use, perhaps bumping it up again.

 

[cfherrman]

What test kit do you have?

 

[Ms1780]

I have the Taylor K-2006

 

[Akathisia]

Pool School - Chlorine / CYA Chart

 

[Richard320]

Set up pool math with your surface and chlorine source and TFP and it will automatically calculate the minimum and target levels that you can then plug in higher up. Don't be alarmed by the high FC.... it's actually going to be no harsher than tap water due to the buffering effect of the CYA. And while it may take a fair amount of bleach to get to the target, the daily maintenance dose should be about the same as someone with lower CYA and FC targets.