New pool owner, (40,000 gal in ground vinyl lined) learning crash course style. Had pool guy out to get started, after his visit had trouble keeping chlorine up, turned up dispenser on tablets, figured out mistake later. Now pH stays quite low (6.6 or lower), even with adding chemical, cya levels around 150, chlorine hard to keep up. (All other levels test in ideal range) Read up, see that we need to drain water out and add fresh to lower cya. Planning to drain roughly 30% of water and refill and repeat 2 or 3 times til cya level at 30 to 40 ppm. My questions are is this the right strategy, and what do I need to know about draining and refilling before I make another mistake?!? Thanks!
How to drain and refill pool to lower cya
- Thread starter Laura Padgett
- Start date
Welcome! 
Sounds like you've done enough reading to know about leaving some water in the pool to keep the liner from shifting. We like that.
Another worry is, are you on a well? That might limit the amount you can refill at a time.
If you want to get it done in one big push, there's the tarp method. Drain and refill in progress - fill water results!! You'll need a giant tarp that can span the pool and slide down the walls But you could empty from below and fill from above until you get rid of as much water as you want and never leave the liner without pressure on it. At the end, you just shove the tarp in and let the fresh water spill out into the pool as you haul it out.
Otherwise, just pump water out until you have a foot left in the shallow end and refill, the way you planned.
Sounds like you've done enough reading to know about leaving some water in the pool to keep the liner from shifting. We like that.
Another worry is, are you on a well? That might limit the amount you can refill at a time.
If you want to get it done in one big push, there's the tarp method. Drain and refill in progress - fill water results!! You'll need a giant tarp that can span the pool and slide down the walls But you could empty from below and fill from above until you get rid of as much water as you want and never leave the liner without pressure on it. At the end, you just shove the tarp in and let the fresh water spill out into the pool as you haul it out.
Otherwise, just pump water out until you have a foot left in the shallow end and refill, the way you planned.
Using aquacheck select and a cyanuric acid insta-test.
- - - Updated - - -
If we drain from bottom deep end and fill at shallow top will that work at all without the tarp?
- - - Updated - - -
If we drain from bottom deep end and fill at shallow top will that work at all without the tarp?
When it is refilled and cya levels are in desired range, after I check other levels (tap water seems pretty close in everything) and assuming they are correct, how much chlorine should I expect to add and how frequently, and should I use the chlorinator with tablets at all? It will be direct sunshine all day 90+ temps.
You have a giant pool. I expect you'll be using a jug of bleach a day, possibly as much as 2 jugs if it gets a lot of use. That's daily.
The pucks can be used up to a point, but they add CYA. So when your CYA hits the practical limit, they have to stop. Otherwise you're begging for an algae bloom and another drain to reduce CYA to something you can work with.
Have a 36,000 gal pool. CYA reading is 70. I shut off my chlorinater and don't plan on ever using it again. How much water needs to be drained and refilled to get the CYA to a tolerable level
2/7
Easiest way is to figure out your average depth and empty water until you're 2/7 of that down, plus a little extra to be safe. Just don't go lower than a foot in the shallow end, lest the liner shift and wrinkle.