Help - Chlorine being used up - Harsh Cl Smell

SBax

Active member
Jul 3, 2009
37
Eden Prairie, MN
FC = 10 ppm
pH = 8.0
CYA = 35
TA = 90
CA = 170

Everything was going well then the Cl dropped to 0 on Monday.
Tues added 8 ppm Cl
Wed 1 ppm Cl, pH 7.8
Thru eve add 10 ppm Cl and 300 ml muriatic (37%)
Fri morn still 10 Cl but pH is now 8.0
And, now the pool has a sharp Cl odor, not the usual Cl-type smell - more pungent.

Test reagents checked ok

Thanks for any advice

25,000 gal
vinyl
 

svenpup

LifeTime Supporter
Nov 18, 2009
835
Sacramento, CA
Anona, I think SBax does have a CC test...in the form of smell. :eek:

Whatever used up your FC has taken hold and you should shock (process link in my signature) to get ahead of it so you can start holding FC again and get rid of those CCs (and that smell). Of course an FAS/DPD test that allows you to test FC up to shock levels and CC is really the way to go.
 

duraleigh

Admin
Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Apr 1, 2007
32,859
Sebring, Florida
Use as much muriatic acid as it itakes to get your pH down around 7.2-7.4 and then shock the pool according to the procedure in pool school. That will clear your pool and get rid of the smell.
 

SBax

Active member
Jul 3, 2009
37
Eden Prairie, MN
Thanks a lot. I suspected this.

But, oh no. I have a big pool party tomorrow. Cannot shock.
Does this increase the possibility of eye irritation? Anything else I should worry about?

Big thanks.
 

SBax

Active member
Jul 3, 2009
37
Eden Prairie, MN
Ok. I have a chloramine problem. Last weekend the pool had very high usage which may have been the start. Another problem may be I actually test for Total Chlorine (TC) not FC.
 

SBax

Active member
Jul 3, 2009
37
Eden Prairie, MN
OK thanks. Problem is I can only measure TC.

I have an idea:
1) Adjust pool pH to 7.5
2) Bring water to pool store and check FC.
3) Measure same sample with my TC too. This will give me FC, CC, TC
4) Calculate and raise FC to 15 ppm with fresh bleach.
5) Check TC right away and subtract the CC reading from the pool store. Maintain this TC level all night.

Am I on the right track?
 

SBax

Active member
Jul 3, 2009
37
Eden Prairie, MN
Came home to absolutely no chloramine smell. None at all. 12+ hours of sun.

Bought a new test kit.
pH = 7.5
TC = 5.0

My usual method titrates at 3.5 TC.

Pool store says
pH = 7.4
FC = 4.0
CC = 0

So, I'm relaxing and confused but not worried.
 

anonapersona

TFP Expert
LifeTime Supporter
Nov 5, 2008
2,598
Great, now run that FC up to the top of the range right as the party is about to start, or rather an hour before. With CYA 35 that's be shock at FC 14. Let the party begin there and trust that all the action, the dirty feet, the sweat, and so on will take that down pretty quickly. Take a quick test if you can during the party or at least right after. Run the FC back up to 14 after the party as you close it down for the night and let the pump run a bit longer than normal.

If it is a day long thing, with lots of kids or babies or dogs, then you will probably want to check after 4 or 5 hours and if FC looks like it might get below 3 before the party is done you may want to blow a whistle and clear the pool for a quick addition of chlorine plus a 30 min sit out time.
 

JasonLion

TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
37,880
Silver Spring, MD
By far the best thing to do is to get a test kit that can actually measure FC and CC. Pool store test results are sometimes fine, sometimes wildly off, so you really can't depend on them. Also, CC can change when you add chlorine, either higher or lower, so you can't assume that it remains the same.

Chlorine plus sunlight gets rid of CC. So it isn't surprising that the smell is gone. As long as you maintain the correct FC level, you will be fine.
 

SBax

Active member
Jul 3, 2009
37
Eden Prairie, MN
anonapersona said:
Great, now run that FC up to the top of the range right as the party is about to start, or rather an hour before. With CYA 35 that's be shock at FC 14. Let the party begin there and trust that all the action, the dirty feet, the sweat, and so on will take that down pretty quickly. Take a quick test if you can during the party or at least right after. Run the FC back up to 14 after the party as you close it down for the night and let the pump run a bit longer than normal.
...
I'm doing that. Still no cloramine smell. pH 7.6. Thanks Jason and everyone.