Calcium Hardness raising. Why?

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Joe_Fire

Joe_Fire

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LifeTime Supporter
Sep 20, 2012
16
South Florida
This is my first post so go easy on me. Pool was finished last October and I've been following the TFP guidelines for my chemistry.
Using the TF-100 kit.
Current levels
FC-3
PH 7.5
TA 60
CYA 80
Salt 3300
CH-540 :hammer:

I usually have to add acid a couple times a week to keep th PH under control. The CH has been steadly climbing and I don't know why. I haven't noticed any scaling, but the clarity is a little off.

My question is what is causing it and is this a real problem.

I'm not really interested in draing half the pool water. As I'm in South Florida lots of rain should be diluting it. (it worked for my CYA and Salt)

Thanks
 
It can become a problem. Some is likely coming out of the plaster, and the rest is due to evaporation and refilling.

Don't you get rain down there in the summer? Divert a downspout into the pool and dilute it. Warning: the first inch or so will sweep all the dust and debris in, so give the gutters a chance to clear before you start filling.
 
Are you adding acid slowly over a return flow and perhaps brushing in the area where you add acid to ensure thorough mixing? If not and you add it too quickly in one place, then is there any noticeable deterioration (pitting) of the plaster in the area where you are adding acid? You might be dissolving some of your plaster (the calcium carbonate portion) into the water. Hopefully not, but I'm just putting that out there as a possibility. Seems unlikely though since the quantity would be rather large so would normally have to involve a huge amount of surface area of the pool, not just one place where you've been adding acid.

The CSI is negative (-0.4) though not extremely low and if this was soon after the re-plaster then I could see how that might dissolve new plaster more readily, but it's been long enough that I would have expected that to have cured by now. I don't think the cloudiness is due to calcium carbonate since your CSI is negative so your water is not over-saturated. Basically, your high CH isn't actually too high given your other water parameters. I would not try and lower it. It's more likely that your FC of 3 ppm is not enough for your CYA level of 80 ppm and you may be starting to get algae so may need to shock the pool and then keep a minimum FC (after you come back down from shocking) of 4 ppm.
 

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I'm usually pretty careful about adding acid. Mix it in a bucket of water an pour slowly into the deep end. Usual dose is about 20 oz.

Cleaned the SWG yesterday, added a little bleach, and let the filter run all night with the Great White cleaner scrubbing away.
This morning's results

TC/FC 6
PH 7.5
TA 70
CH 500
temp 87
Visually water looks clearer. :wave:

The other thing I thought of is, after a couple of days of heavy rains the water does overtop the coping (which is natural travertine marble) I don't drain it down just let nomal activity splash it out.
Is there a chance the water is breaking down the stone ? It looks ok no noticeable degrading,
Just a thought.
 
Rain does tend to contaminate pools depending on what gets washed in, but in your case it does sound more like algae growth that was getting started and that the elevated chlorine level is killing it off. Shocking the pool would kill it off faster (and is what would normally be recommended), but so long as you are making progress you're doing OK -- just don't let the FC drop too low or the algae will grow faster than chlorine can kill it. If you find you get stuck, then shock the pool by elevating the FC to a much higher level than you are doing.
 
Thanks for the help chem geek.
I didn't have enough chlorine to shock to 21 as the Pool Calculator indicated. So I set the SWG to "Super Chlorinate" and let it run all night.
This morning FC is at 21ppm.
I shut the SWG off.
Should I keep it off untill the Chlorine comes down to 6?
Or just leave it on it's normal setting
Water looks good btw.

Also what effect on the CH would adding borates have. I've read about the benefits of 50ppm and have considered doing it. But I think I'll wait a week or 2
 
Joe_Fire said:
Thanks for the help chem geek.
I didn't have enough chlorine to shock to 21 as the Pool Calculator indicated. So I set the SWG to "Super Chlorinate" and let it run all night.
This morning FC is at 21ppm.
I shut the SWG off.
Should I keep it off untill the Chlorine comes down to 6?
Or just leave it on it's normal setting
Water looks good btw.

Also what effect on the CH would adding borates have. I've read about the benefits of 50ppm and have considered doing it. But I think I'll wait a week or 2
Click to expand...
Leave the chlorinator on. The shock process is about maintaining high FC for a long period of time, not a one-time megadose.

It might be time to reread pool-school/shocking_your_pool
 
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