Super high calcium. How much should I drain

[Grione45]

I just bought a top of the line testing kit and oh boy what a shock. Let me back up. I have a nice clear pool but getting a tiny bit of greenish/yellowish algae in the shady side that appears after about a week. Brush it and it goes away but pops up again about a week later. I tested my water and this is what I got. BTW my tap water measures 60 ppm calcium hardness. I am assuming I should drain part of the water but how much. Also I would like to stop using the solid sanitizers and switch to liquid after reading the recommendations on this forum. Any other suggestions would be appreciated. I have owned this pool for 20 years and starting to realize I don't know a heck of a lot about how to maintain it! Thanks.....Mark in Fresno

Free clorine.............5.2
No measurable combined clorine
PH...........................7.6
TA...........................110 ppm
Calcium hardness.....625 ppm
CYA.........................100 ppm

 

[JohnT]

Welcome to TFP!

What is the hardness of your fill water? That can make a big difference in how much you need to replace.

If you'll check out the Chlorine/CYA chart you'll see that your chlorine level is too low for 100ppm CYA. That may be the source of your algae issue.

 

[linen]

Welcome to tfp, Grione45

Which kit did you get?

Your CH is high but can be managed, however the high cya is a problem. It maybe that your cya is even higher than 100 ppm, since most cya tests are not that accurate up above 100. Assuming you are using a liquid cya test, I would repeat that test using 1/2 pool water and 1/2 cya free water (tap water is fine for this) and multiply your result by 2 to see a better approximation of where your cya is.

 

[Grione45]

I have the Taylor K-2006 testing kit and the calcium hardness of my fill water is 60ppm..

 

[linen]

So it seems that you have been using Cal-hypo to chlorinate?

What you describe sounds like mustard algae. Before proceeding with that though, you need to get the cya level (and by default this will also lower the CH level) by doing a drain refill. Perform the cya dilution test I described above and post your results so we can better know how much of a drain/refill you need.

 

[Grione45]

Hello there linen,
I performed the test you suggested for the CYA and my results came out to 140, and to answer your second question I have been chlorinating with the trichlor pucks and the occasional cal-hypo shock.

 

[Patrick_B]

Hey Grione, welcome to TFP. Linen is right about your CH, but if you get the CYA down to normal levels it will automatically correct the CH as well if you use that fill water. In the future, I would go with manual additions of bleach for your FC. It will be very easy with that size of pool.

 

[Grione45]

Thanks for the advice everyone, much appreciated. Also Brushpup, by manual additions of bleach do you mean liquid chlorine? Also hoping to hear back from Linen on how much he/she thinks I should drain.

 

[linen]

Well since your cya is ~ 140 ppm, that means you need to drain about 64% of your water to get to 50 ppm (or recommended level). Do you know what your ground water level is? If you are uncertain, then you may want to drain about 1/3 twice and see where your cya level is then drain again to get it below 50 ppm (this will use more water). By the way linen=he :-D

 

[Patrick_B]

Thanks for the advice everyone, much appreciated. Also Brushpup, by manual additions of bleach do you mean liquid chlorine? Also hoping to hear back from Linen on how much he/she thinks I should drain.

Yes I do, same thing, different name. Liquid Chlorine is Bleach is Liquid Chlorine.

Bleach will not have the side effects that Calcium Hypochlorite or Di-Chlor/Tri-Chlor will have.

 

[Grione45]

Linen, my groundwater is 60ppm. It doesn't look like it will be physically possible to get to 50ppm. ....Mark

 

[duraleigh]

Linen, my groundwater is 60ppm. It doesn't look like it will be physically possible to get to 50ppm. ....Mark

Hi, Mark,

You are mixing up your parameters. Linen means 50 ppm CYA. There is no CYA in groundwater so I think you are getting CYA and CH intertwined.

To add what others have said, your CYA is a far bigger issue than your CH but draining your pool down in a series of drain/refills will solve both at the same time.

 

[Richard320]

What they said. The high CYA is a bigger problem. I have much higher CH than you, and it IS manageable, although you have less wiggle room with pH and TA when it starts approaching 800.

I periodically use a pump to drain a few inches out of my pool and use it to water the lawn, and use the water that would have gone to the lawn to refill the pool. Same usage, it just passes through the pool first. If we ever get any decent rain, that's when it's time to seriously start replacing water. I divert one of the raingutter downspouts to my pool, using the spa as a settling basin, so I can grab as much CH and CYA free water as I can. Once the storm ends, I just set the filter to spa only and it clears it up in about twenty minutes.