CH at 900. Do I need to drain and fill immediately?

[peterl1365]

I'm in Southern California and my pool got a lot of dirt and ash dumped on it from last week's wildfires. The CH has been rising steadily from about 200 when the pool was filled in March to 500 about 6 weeks ago. My most recent test was 900. Granted, this was done by the young kid at my local Leslie's, but I presume it's accurate to +/- 100 ppm.

He mentioned something about waiting until the spring to do a drain and fill. Does this make sense? What are the consequences of high CH?

Other numbers:

CL ~6-8 ppm
CYA 60
TA 80
pH 7.7

TIA

 

[giulietta1]

My most recent test was 900. Granted, this was done by the young kid at my local Leslie's, but I presume it's accurate to +/- 100 ppm.

I wouldn't. Pool store tests can be WAAAAY off. Do you not have your own test kit? If not, get the TF-100 or the Taylor K-2006 (FAS-DPD complete).

He mentioned something about waiting until the spring to do a drain and fill. Does this make sense? What are the consequences of high CH?

Scaling, calcium deposits on surfaces. . . looks unattractive in your pool and can, at extremes, lower the efficiency of your equipment from buildup on the interior of pipes.

I'm pretty sure that the knowledgeable folks here will agree with me on this. . . don't even THINK about anything as extreme as a drain-and-refill until you've done your own tests with a reliable kit.

 

[mas985]

We have high CH fill water here in No CA so I usually wait until Feb to do refills. I am close to 700 ppm now (started at 200 ppm in Feb). During the rainy season, more surface water is used in the city water so the CH drops making refills less/shorter.

If you do wait, keep your PH on the low side to avoid scaling.

 

[JasonLion]

With high CH you need to keep your TA and your PH lower to compensate. If you keep your PH between 7.2 and 7.5, and TA doesn't go up, you should be alright even with CH around 900. You could lower your TA a little to get a little more flexibility. Long term you will need to deal with the CH level, but doing it right now isn't critical as long as you keep an eye on your PH.

 

[peterl1365]

Thanks for the advice everyone. That is exactly the info that I needed.

 

[chem geek]

We have high CH fill water here in No CA so I usually wait until Feb to do refills. I am close to 700 ppm now (started at 200 ppm in Feb). During the rainy season, more surface water is used in the city water so the CH drops making refills less/shorter.

I took a look at your water quality report for Pleasanton. Though Total Hardness was around 340 ppm, Calcium was 76 ppm presumably as Calcium, not Calcium Carbonate, so that would make Calcium Hardness about 190 ppm -- pretty darn high. With evaporation and refill that can build up. Annual evaporation is around 60" per year and this is mostly in the summer so that's 5 feet so more than the typical 4.5 foot average depth. So you'd expect the CH to rise each season by 200-250 ppm to 400-450 ppm (i.e. roughly more than doubling). I'm not sure why you see it even higher than that (i.e. 200 to 700). Maybe the evaporation rate is higher than the average (perhaps there's more wind or less humidity).

Richard

 

[peterl1365]

You know, I hadn't even thought about evaporation as being a primary culprit in hardness buildup. The water quality where I am (Murrieta, CA) is not quite as high as Pleasanton, (291 average hardness, 80 as calcium), but it is in the same range. We may have higher evaporation rates here compared to N. Cal since my area is basically a desert. 110 degrees are common in the summer, with around 30-50% RH.

I had been worried that somehow my pool water was leaching huge amounts of calcium from the plaster. I now understand that this CH rise will be an annual occurrence.

As always, Richard, you've been a great help.