Losing Chlorine Too Rapidly

[CraigSm208]

I’m near my wit’s end.

I’ve been using the BBB method for 5 years and it has been very successful. However, I’m having a problem this year holding chlorine.

This is the 3rd time in a row this situation has happened this season. Here’s the info for the latest occurrence:

Readings as of 7 AM this morning, June 25th
FC = 9.5
pH = 7.6
TA = 140
CA = 300
CYA = 40
Ammonia = 0.0
Phosphates approx. 200 pbb

6/23 3:00 PM – Brought the pool up to shock level (16 ppm)
7:30 PM – FC = 16.0
Ran the pump all night.

6/24 6:45 AM – FC = 16.0 (OFCT seemed to be successful.)
1:45 PM – FC = 15.0 (Opaque covered had been closed until 1:45 PM)
5:30 PM – FC = 13.0 (Pool had been exposed to sunlight and 4 teenagers for 3 hrs and 45 min.)
7:00 PM – FC -= 12.5
Pumped turned off at 7:45 PM

6/25 6:00 AM – Pump turned back on.
7:00 AM – FC – 9.5 (Lost 3 ppm in 12 hrs while the cover was closed and the pump was off)

This is the 3rd time in a row that this has happened. Overnight Free Chlorine Test indicates there are no algae in the water. Then over the next day or two the chlorine level drops significantly indicating there is something consuming the chlorine.

I’ve pulled the light and cleaned behind it. I’ve brushed the entire pool. I’ve swam using a mask looking for any discoloration on the liner and found none.

Any suggestions?

Thank you.

 

[steinholder]

Combined Chlorine is a very important test result, that is what tells you if you have something consuming your chlorine.

 

[Bama Rambler]

Exactly how much FC are you losing per day in ppm?

 

[CraigSm208]

Bama Rambler - From 7:00 AM Sunday to 7:00 AM today (Monday) I lost 6.5 ppm. The pool was open to sunlight about 4 hours of that time and the pump ran about 9 hours. On the other two occasions like this, the water eventually turned cloudy.

 

[Bama Rambler]

That's a lot and with it being closed it surely seems like something is going on but I don't know what. Have you brought it to shock level?

 

[Thinkly]

Combined Chlorine is a very important test result, that is what tells you if you have something consuming your chlorine.

+1

 

[CraigSm208]

Bama Rambler - Yes, I have brought it to shock level. I did the shock method as outlined in the Pool School. I didn't quit bringing it to shock level until the Overnight Free Chlorine Test showed no loss and the water looked clear. I never have much CC chlorine. It is always 0.5 for less. I've been using this method for 5 years and I've never experienced a problem like this. I've considered bringing the shock level to the mustard algae level. Do you think that would be a logical next step?

One other thing, when I look in the skimmer there is a film floating on the water with a few big bubbles in it. This covers maybe 1/3 of the water surface in the skimmer hole. Does that indicate a problem? I don't think it is sunscreen residue.

 

[Bama Rambler]

MAybe it's time to clean behind the light and everywhere else something could be hiding.

 

[CraigSm208]

Yes, I've done all of that - cleaned behind the light, brushed everywhere, even put all the "toys" in the shocked pool. Do you thinking bringing the pool to mustard algae shock level would be warranted?

 

[harleysilo]

What about the waterside of your auto cover?

 

[CraigSm208]

Harleysilo - Actually, I've wondered about the waterside of the auto cover. When I shock the pool, the cover floats on the shocked pool. Shouldn't that deal with any algae on the cover? How would I clean the cover?