Low Chlorine Problem

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epechart

epechart

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May 14, 2017
14
Hanover, PA
Pool Size
28000
Surface
Plaster
Chlorine
Liquid Chlorine
I have been battling this low chlorine problem all last years swimming season & now again this year. Last year the pool store just kept telling me to add chlorine & to shock the pool every week. They finally said they didn't know what to do so they had me use Aqua Finesse for several weeks but that did nothing either. I was also constantly adding Alkalinity Rise.

Last year the calcium hardness range was 430-484 but they told me it was a little high but not to worry about it, that rainwater & adding water to the pool would help to bring it down. According to the TF-100 test kit, the CH is 975!!! Could this be correct? Pool Math says to replace 73% water replacement. That is a strain financially since we are on city water. We replaced about 75% of the water a few years ago because the pool store said it had nitrates in the water.

I found Trouble Free Pool site recently & have been reading, reading, reading. I never knew anything about water chemistry before & just relied on the pool store. Whatever they told me is what I did. I spent a horrendous amount last year trying to get the chlorine to stay up. Never did the pool store suggest I replace the water. For the amount I spent for chemicals, I could easily have replaced the water & had some left over.:(:(

Here are my readings taken today:
PH 7.8 (the last 2 days I have added 1/2 gal Muriatic acid ea day) Prior to that the PH has been 7.5
FC 1
TC 3
TA 170
CYA 40
CH 975

Since 5/26 I have added 7 gals Clorox 8.25%, 6(1 lb) bags shock (that I had left from last season), 4 lbs cyanuric acid (from Lowes).

The pool looks great but not sparkling clear.... the numbers are atrocious!

I'm asking for advice before I do something that I should not have done. I know a lot more since I found TFP but still am not confident to decide what to do.

I am at my wits end.

Thanks.
 
Welcome to Trouble Free Pool (TFP)!

My first suggestion is to go pickup more bleach. Don't get Clorox, generic store brand as long as it says 8.25%. I used ot get the WalMart Great Valu brand, but my local grocery store has the same price now so I don;t have to deal with WalMart. Get about 10 bottles for now.

Add 2 bottle immediately with the pump running. That should bring you from FC 1 to FC 7. Test again in 60 minutes. Use Pool Math to calculate how much you need to get back to 7 Do that until this afternoon. When the sun goes down do it one last time. Wait 60 minutes with the pump running and test once more - don't add bleach. That will be your starting number for your Overnight Chlorine Loss Test

Tomorrow morning you will test again early, before the sun is on the pool. That is your ending number for the Overnight Chlorine Loss Test

This will tell us if you have something growing in the water and if you need to SLAM Process
 
I have a feeling the majority of the solid chlorine you have been using is cal-hypo. That would drive CH to those levels.

You may need to reduce that with a partial drain / fill. Need to know what your fill water CH is. I believe you backwash with that type filter so that will help. Also pump out some water before each rain storm.

Good Luck.
 
mknauss said:
I have a feeling the majority of the solid chlorine you have been using is cal-hypo. That would drive CH to those levels.

You may need to reduce that with a partial drain / fill. Need to know what your fill water CH is. I believe you backwash with that type filter so that will help. Also pump out some water before each rain storm.

Good Luck.
Click to expand...
Building on this, I was dealing with high CYA and installed a system to harvest rainwater from the roof gutters and put it in the pool. This may help if you can work it out.
 
Yes....I'm pretty sure the solid chlorine ingredient was cal-hypo. OMG....I have used that for years!!

Also, I'll check the fill water CH...never thought of that. Yes....we do backwash with our filter system.
 
Yup, you need to SLAM Process

Only two things cause the level of chlorine in the water to go down:

- UV rays of the sun

-Organic matter in the water the chlorine is trying to eliminate

As you FC level went dow overningt (no UV rays of the sun) there is something growing in the water that the chlorine is trying to eliminate. Time to give it more chlorine via the SLAM Process
 

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I have a few questions before I start the SLAMing process.

I am considering replacing the water. Even if I get the chlorine/algae problem solved, I still have the high calcium hardness problem which is eventually going to damage the plaster. I might as well bite the bullet & replace it. It will cost about $400.

A few years ago we replaced the water two different times/two different years because the pool store thought we must have nitrates in the water causing the low chlorine problem. I read that someone said the pool water should be replaced every 2-3 years....is that correct? I never heard that before.

Last year the calcium hardness was around 430-485 range according to the pool store. Those were the different readings throughout the year. Is it possible to now have a reading of 975? I do the test exactly how the TF-100 test kit describes but I was wondering if I could be missing something.

We never had problems like this before the pool was remodeled....my husband seems to think the new plaster has somehow caused the problems we have although the remodel job was done in 2008. (he knows even less than I do about water chemistry....although since being here at TFP I know a lot more than I ever knew about pools...thanks to you all).

I read about reverse osmosis but that's not an option for us. So it will cost around $400 to replace the water. PoolMath says about 73% needs to be replaced. Our city water tests CH 100.

Am I missing anything that I should be considering before replacing it?
Thanks again.
 
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