Chlorine numbers are way off

[tedricci]

Here's the deal: Pool is clear, but for the last couple of weeks, chlorine numbers have been in the .5 - 1. range for FCL and .9 - 1.6 TCL. My CYA was at 30 so I added 6# to raise it to approx. 60PPM, it's at 38 today. Yesterday, I added 2.5 gals of 12.5% shock and 3# of powdered shock since the pool was cloudy and the numbers were so low. During the night the SWG worked for 8 hours (at 70% output) adding more chlorine to the pool. This morning the FCL was.06 and TCL was 1.2. What happened to my chlorine? I expected to be in the teens still. Pool pump runs 24/7 for a turnover of approx. 21k per 24 hours.

Fiberglass 20k, SWG and sand filter.

Today:
FCL 0.6
TCL 1.2
Ph 7.6
TA 90
CH 260
CYA 38
Salt 3.4k

I'm stumped. I was told it's chlorine lock and advised to use 6# of an oxidizing shock to break this situation. Any suggestions?

Thanks

 

[JamesW]

You need to follow the Slam procees. See pool school for instructions.

 

[JohnN]

Chlorine lock doesn't exist. What does exist is organics (like algae) growing in your pool constantly eating your chlorine. What you need to do is order one of the recommended test kits (linked in my signature) and then SLAM the pool (also linked in my signature).

 

[Donldson]

Firstly, Chlorine Lock is the pool industry equivalent of Gremlins. When they tell you that they either don't have a clue or don't want to explain what is actually going on. I always assume the former.

The numbers you posted are very suspect, I'm guessing pool store testing? First thing is that if you have added stabilizer, whether it shows up on the tests yet or not assume the CYA is in there, so treat your pool as if it the CYA is 60. We need to know what the active ingredient of the 3 pounds of powder "shock" you added was, do you still have the bags?

Since your chlorine is hanging low there are organics, most likely the cloudiness is algae that is about to become a big problem. Do read about the SLAM process and make sure you have everything you need to do that. A traditional shock prescribed by the pool store will not be appropriate here, especially since they appear stumped and telling you it's chlorine lock.