Pool won't hold chlorine

Jul 25, 2013
6
Tucson, Arizona
#1
I've had trouble lately keeping a decent reading of FC. After shocking with either trichlor shock powder or bleach, it goes down rapidly. I usually keep at least 3-3in. trichlor tablets in the floater as well. It's also difficult to raise pH above 7.1 or so, even when adding 2 - 3 times the recommended amount for the pool size. The latest test results from local pool store show VERY high readings in some areas, to the point that I suspect they may not be accurate.

FC 1
CC .2
pH 7.1
TA 240 (!)
CH 600 (very hard water in my area)
CYA 250 (!)

With numbers like these, should I just do a couple of half-drains and fills to bring numbers to more reasonable levels instead of pumping in more chemicals to try to make the adjustments? Thanks for any info or insight...
 

linen

TFP Expert
LifeTime Supporter
Jul 30, 2010
8,649
Twin Cities, MN
#2

pwrstrk

TFP Expert
LifeTime Supporter
Aug 17, 2012
4,758
Elverson Pa.
#3
Welcome to TFP

The pool store testing is unreliable. Their in business to sell chem's.

Take some courses in pool school. Tons of good info. You need a reliable test kit like the ones we recommend. It will be your best friend. Its hard for us to help you without accurate test numbers. A trouble free pool will be hard to have without it.

How does your water look?




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Jul 25, 2013
6
Tucson, Arizona
#4
Test results are from a local store; I've read that they can be notoriously inaccurate for CYA, but I don't have anything to compare it to. It's a vinyl KD pool. Can high CYA cause chlorine to be used rapidly? And is it normal to both high TA and low and/or difficult-to-raise pH?
 
Jul 25, 2013
6
Tucson, Arizona
#5
pwrstrk - Yes, I'm always a little suspicious of pool stores, especially when they try to sell me chemicals... In this case, the tester didn't try to sell anything... He was the first to recommend the half-drain and refill.
 

Donldson

TFP Expert
LifeTime Supporter
In The Industry
Jun 12, 2009
3,268
NW Ohio
#6
I would love to know how they tested CYA, but if it's true it's certainly sky high. High CYA wouldn't increase your chlorine usage, more likely you have organics. With an FC of 1 and a CYA of... well, a lot for sure, you don't have high enough available chlorine to battle it. If it really is 250 you would need a minimum FC of 19, but if it really is that high you will have to replace 80% of your water to get it under control, half isn't going to cut it.

It is also rather unusual to have high TA and low pH, the TA will draw the pH back up. Your problem is probably the highly acidic trichlor keeping the pH down. If you have been shocking with trichlor powder then I would blame it on that.

First thing is first, if that CYA number is true then you need to get it down before bothering with anything else. No reason to treat water you are going to drain!

And welcome to TFP! :wave:
 

pwrstrk

TFP Expert
LifeTime Supporter
Aug 17, 2012
4,758
Elverson Pa.
#7
Sun and organics consume chlorine. If that CYA level is correct you would have to keep a very high FC level to keep algae at bay. That's why I asked how does your water

I would consider getting one of our test kits.


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Jul 25, 2013
6
Tucson, Arizona
#8
pwrstrk - Oops... forgot to mention water appearance... It actually looks very clear, with no visible signs of algae. Lots of intense direct sunlight is a pretty much a constant condition in Tucson summers, but the levels of chlorine I now need is much greater than in the past. Reading more in Pool School, I can see that using trichlor tabs and shock have contributed to the accumulation of CYA over the years, and that high TA does indeed require more soda ash or borax to raise pH level. It's beginning to look like the half-drain and fill - perhaps a couple of times - is the best option (?)
 
Jul 25, 2013
6
Tucson, Arizona
#9
donldson - Yes, I figured that a single hald-drain and refill won't do the trick, but I hesitate to drain more than that all at once out of a vinyl AG pool. Doing it twice should, theoretically, replace about 75% of the old water.

Oh, and to all who've responded... The help is much appreciated, and thanks for the multiple welcomes to TFP.
 

Donldson

TFP Expert
LifeTime Supporter
In The Industry
Jun 12, 2009
3,268
NW Ohio
#10
The math holds out, that should work. You are right, it's good to do it in stages with a vinyl liner. Assuming the test is right that should get you under a hundred and in to a much MUCH more manageable situation.

You don't happen to have a CYA test in your kit, do you? They are included in some of the 6-way tests. Would be good if you could test that yourself after the first drain to make sure you aren't overshooting it. (Good idea also to do all of your tests yourself with a good test kit, see my signature for more details)
 

pwrstrk

TFP Expert
LifeTime Supporter
Aug 17, 2012
4,758
Elverson Pa.
#11
Sounds good to me also. Keep us posted. I have to mention again about the test kit. Like I said it will help keep your pool trouble free


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Jul 25, 2013
6
Tucson, Arizona
#12
I'm convinced... I need one of the 6-way kits; will do. Thanks again for the info and help. Since I know what to do now, I'm calling this one "solved" ... at least for now; will post updates next week.