What is Correct Level of CH

[Txmat]

My CH varies a lot. Maybe it is me and my testing. I use the TF-100 and it always is difficult to determine how much of a color change is needed to arrive at the number. So my CH may actually be higher. But, I digress. My CH was up to 550 on July 1 when I left on vacation and is now 470. We had a lot of rain and that must have brought it down.

Here are my current numbers

FC 17
CC 0
TC 17
PH 7.2
TA 80
CH 470
CYA 95 (Use pucks to keep the FC up during vacation)

I tested my fill water today and got the following:

FC 2, CC 0, TC 2, PH 7.5, TA 280, CH 270, CYA 0

I know I can manage the TA with aeration and with normal back washing and draining (due to rain) the CYA. CH is the question. The Pool Calculator says my goal should be between 50 and 300. Obviously I cannot get below 270 without using rain water, so 270 would have to be my minimum. According to the calculator I need to replace 85% of my water to get to 300. My question is what is a realistic goal for CH for my vinyl ABG pool? At what maximum level should I absolutely start to worry? And finally, how would you go about lowering the CH - all at once or with normal backwash & lowering due to rain or some other method?

Thanks, Larry

 

[duraleigh]

CH where you are is manageable but it would be a little better below 400. I would drain and refill if water is cheap.

If not, you can manage by monitoring your pH closely and staying in the lower 7's. Also keeping your TA down around where it is.

Personally I would drain and get rid of some of that excessive CYA at the same time.

 

[Bama Rambler]

If you suspect a testing issue with your CH you should invest in a speed-stir magnetic stirrer. It's great for all the tests but especially the Ch test.

Also, when testing the TA did you wipe the tip of the R-0009 bottle between drops with a damp cloth? Static sometimes causes TA to read high because it affects the drop size of the R-0009 making it take more of them.

 

[Txmat]

Bama, Yes I do wipe the tip of the R-0009 bottle between drops. Wondered why this was in the instructions - thanks for clarifying. I have been holding off ordering the speed-stir until I needed chemicals to minimize shipping and handling charges. So Dave, you would recommend 400 as my target CH?

Larry

 

[Richard320]

You're stuck with high CH just because of the water where you live. Forget target - you'll go crazy. All it means is 1) Don't add more by using Cal-hypo to chlorinate; 2) You need to pay close attention to pH and the CSI; 3) Take advantage of any rainstorms by draining the amount they forecast beforehand. I rigged a flexpipe with a stocking filter from one of my downspouts into the pool so a 1" storm yielded closer to 3" in my pool. I stopped the big chunks of shingle grit but I got a lot of sediment I had to vacuum. But at least that rainwater didn't go to waste!

 

[Guest]

Since everyone likes abbreviations (SWCG, CH, CYA, TA, FC, etc.), and since Richards idea of using rainwater may take, I'm wondering if anyone could possibly come up with an abbreviation for "shingle grit"

 

[duraleigh]

So Dave, you would recommend 400 as my target CH?

Pool School suggests 220-350. That doesn't mean your arms will fall off if you end up @ 219 or 351......it's a suggested guideleine. (i.e. 400 would work, but it's at the top end of what's recommended)

As long as you're doing the job, why not make it 300 and be right in the sweet spot?

 

[Txmat]

OK Dave, The Calculator says I need to replace 85% of my water to get to CH 300. With an above ground pool I assume that a major drain such as that will not hurt the pool. I mean the walls will not cave in or anything else bad happen - correct?

 

[duraleigh]

With an above ground pool I assume that a major drain such as that will not hurt the pool. I mean the walls will not cave in or anything else bad happen - correct?

Probably not but do it in stages to be safe. Drain perhaps a foot or foot and a half and then replace. Repeat as necessary.

You could also siphon off the bottom at one side (end) and refill from the top of the opposite side simultaneously so your water level would never change in the pool. Doing it in stages probabaly makes more sense.