New 20X40 IG, Couple questions

[XDM2]

Hello all. Looks like I found this forum just in time. I had a new 20x40 IG Vinyl pool (30k gal) installed last fall. Pool was built, filled (with city water from 3 9k truckloads), and immediately closed for the winter. Concrete deck poured and pool opened first week in April this year. Started the year with pucks and chlorinator and mindlessly went thru 25 lbs of trichlor pucks over 3 months. I'm switching to BBB and quitting the pucks.

Found TFP site and bought TF-100 kit. Here are first numbers from today:

FC 9.5
PH 7.5-7.8
CC 0.5
TC 10
TA 120
CH 150
CYA +/- 60

I'm not very confident in my ability with the CYA test.

Does CYA of 60 seem about right for 25 lbs of trichlor in a 30k gal pool?

Should I do a few partial drains to lower to CYA to 40? The pool gets sun from 7am-7pm every day.

If I did do partial drains I would be re-filling with well water.

Any thoughts?

 

[JVTrain]

If you use Pool Math: Input your pool volume at 30000 gallons. Then go to the bottom of the screen to the Effects of Adding Chemicals tool. 25 lbs = 400 oz of trichlor. This gives FC, pH, salt and CYA change for that amount. If your pool volume is correct, I show 55 ppm CYA resulting if there was 0 to start. You're in the ballpark for sure.

I would not worry about a partial drain to lower CYA. Simply maintain proper FC based on 60 ppm CYA. See CYA/Chlorine chart in my signature. 60 really isn't that excessive for your pool. Just make sure to stick to bleach/liquid shock for the rest of the season. Your CH is low and fairly irrelevant for a vinyl pool so you could supplement some cal-hypo usage if you find a bargain and for convenience. Just don't totally rely on it. Avoid the well water if you can. Introducing the potential for metals in well water is more problem than maintenance with barely high CYA. You'll also drop some CYA this winter if you do any sort of drain for closing, then refill in the spring.

Welcome to TFP!

 

[Razorhog]

Sounds like you are right on track. Your target FC is 7-9 ppm (see the Chlorine / CYA chart in my sig for reference) with a minimum of 5. Completely agree with JVTrain that the potential for iron from a well drastically outweighs the need to drain/refill due to high CYA. A CYA of 60 is fine, it's what I'm using in my pool now. The thing to know is that the higher CYA, the higher the FC level is needed to maintain sanitation and to shock. Getting to your target FC range of 7-9 won't take a lot of chlorine, and small doses will be needed to maintain. However, if you neglect the pool and FC falls below 5ppm, you'll need to SLAM which requires you get the FC level up to 24 ppm and hold it there.

 

[XDM2]

Thanks for the replies and advice. I will run with the current CYA and let it dilute over time. Is there a test kit available to quickly test FC above 5ppm or am I limited to using the FAS/DPD test every day?