CYA off the "best guess" chart. Advice?

[dontremember]

Michael, I've seen bleachcalc and wanted to give it a try (sounds great), but I guess that's one of the (few) drawbacks of being a Windows-free household.

BleachCalc runs just fine in Linux with wine-0.9.11. Dunno about non-x86 systems, though...

Ralph

[PoolDoc]

Hi Scott;

Given that you have extremely high CYA and 7 year old water, I'd definitely go with water replacment. 'Used' pool water does build up residue which tends to make it harder to work with -- things like phosphates, nitrates, and who knows what else.

It's this residue that is behind some of the push to measure TDS, despite the fact that TDS meters (really, conductivity meters) can't distinguish bad 'residue' from benign ionic content, like salt.

Replace as much as you can at one time -- you won't get nearly the effect from replacing 25% 2x as you will from replacing 50% one time.

But, you've got to be safe and draining your pool can definitely destroy it, depending on type and situation.

Ben

[geoeremite]

Thanks Ben. I've already completed one drain/refill cycle and am midway through the second. Drained off about 28", which I'm estimating is about 40% by volume (funny how that works). Drains pretty slow since the waste valve is a standard hose bib and there are no valves in the pump/filter/heater area that can be used to force more water to waste (would have gone faster before cleaning my filter when the back pressure was 35psi rather than 14, ).

I figure 4 passes like this and I should be in good shape. I did verify that my CYA dropped to around 150-175 after the first cycle.

[geoeremite]

Four passes later, it looks like everything is in good shape. Here's the numbers:

FC 5.0
TC 5.0
Ph 7.2
TA 100-110
CH 200-225
CYA 20-30
TDS 400

(Pool store numbers that match the values I was able to independently measure, including FC,CC,CYA.) CYA could come up a hair, but I think that I'm not going to worry about it for a bit. Was glad to see that it held its FC overnight without issue.

[aylad]

Good job, you've obviously done your homework and have a great handle on your pool. Happy swimming!!

Janet