It's raining here in SoCal. Hard. And it will continue for a few more days.

Why does that make me lucky? Because I can dilute the high CYA in my pool without incurring the wrath of the water company! (drought year and all....) My father-in-law loaned me a small submersible pump, which I have in the pool as I type. The pool was getting close to the top; I've pumped out about 4" so far.

I've also emptied the floating tablet chlorinator - gonna switch to liquid Chlorine.

I'll probably still have to empty a lot more water as we approach summer, but it's a start!

Yep, you're lucky! Take advantage...


Welcome to the forum

Ideally you should pump the water out before it rains, as the CYA will not be diluted yet. To use some simple numbers, you have 10 inches of water and it's going to rain 1 inch, and your CYA level is 10 ppm.

If you pump out 1 inch of water before it rains, you are getting rid of one tenth (or 1 ppm) of your CYA, which is now 9 before the weather adds the 1 inch back.

if you wait, you'll end up with 11 inches of water and 10 ppm CYA. Now if you pump the water out, you are only getting rid of one eleventh of your CYA (roughly .9 ppm).

If you exaggerate the numbers, the difference is more drastic.

To finish what baudilus and polyvue started: If you drain the 1" before it rains, you end up with 9.0ppm. If you drain after, you end up with 9.1ppm. The effect is small, but cumulative.

The same principle applies to a major drain; you want to do as much as possible up front, because that gets you the most benefit.
--paulr

That's only true during evaporation - if he pumps water out he's also pumping out CYA.

Obviously the numbers assume a perfectly even distribution of CYA, which is unlikely to be true in reality but the numbers should be close enough to be negligible.

The 10ppm is a rate-per-volume, which we are assuming is perfectly evenly distributed, and that necessarily means that if you pump out 1", the water you pumped out and the water left behind each still has 10ppm. The absolute total weight of CYA in the pool has gone down, but so has the amount of water, so the rate-per-volume (i.e. amt-of-CYA divided by amt-of-H20) has not changed. Then you dilute the 9" by adding 1" of CYA-free water, and the overall rate-per-volume goes down to 9ppm.

With evaporation, you are removing water but not CYA, so the absolute amount of CYA has not changed but the amount of water has. In that case amt-of-CYA divided by amt-of-H2O will get you a higher concentration. Replace the evaporated water and you are back where you started.
--paulr

Richard-

I may be able to refer you to a company that can not only lower your CH, but also your CYA, without incurring the wrath of the water company and save the vast majority of your existing water, depending on where you are located in S. California. PM me if you would like me to provide that info.

Thanks for your concern, guys, but I already figured out that it would go better if the pool was emptied in one shot. But sometimes people are at work and can't drop the level before the fresh water hits it.

Anyway, it's raining again - heavy - and the submersible pump is on. I've also diverted a raingutter downspout (with sediment trap) into the pool. 1" of rain may get me 2" in the pool, maybe even 3"! Every little bit helps. With the amount of rain we've been getting this year, maybe they'll call the drought over soon. Then I can do a proper drain and refill...and also increase my baseline usage for the next drought year calculations.

I wish. But the reservoir and groundwater deficit is too big, in my opinion. If we get 2-3 years in a row like this, maybe we'll make some progress.
--paulr

Harrumph! Now you're talking like one of those Northern California tree-huggers!

In Southern California, people water their lawns no matter what. And the sidewalk, the driveway, the street, and the gutter. It's only water - and there's plenty more where that came from - we'll just pump the Owens Valley dry! It drives me nuts - I moved south a mere three years ago. I used to live near you - 25 years in Cambrian Park, 10 years across the street from Westgate, and another 10 years in downtown Campbell. We might as well split the state in half, because they are totally different.

Ah, I see my simple mistake, although my end result was still correct. Thanks!