Whats eating my chlorine

[CHSRpool]

So I have a 35,000 Gal indoor play pool running a SWG and a stenner pump liquid chlorine feeder. The SWG is currently down (awaiting cell replacement) so I have been using my liquichlor chemical feeder pump which was working fine the last week. Yesterday my FC/TC levels just dropped and will not rise up much at all when leaving my chlorine pump on for hour or so. I have ruled out the stenner pump chlorine feeder being the issue, chlorine is reaching my return line. I am thinking about shocking the pool tonight to bring up the levels. Here are my latest test results: FC 0.10 TC .30 PH 7.8 ALK 120 CYA 14 CH 280

 

[BuckeyeChris]

The minimum the FC could be in the test kits we suggest is 0.2. For CYA we usually round up to the next 10, and the minimum on the test is 20, so you have some other testing method going on).


Adding 6 gallons of straight 6% bleach should raise your FC by 11 ppm. That would be the shock level for a pool with 20 CYA.

Turn off all the stenners and SWG, run the pump, and add the bleach. About an hour after adding, take a FC reading. Let the pump run overnight/8 hours and then test FC again.

 

[kimkats]

How are you testing your water? THAT will tell us the big picture and may allow us to trouble shoot your pool.

Kim

 

[CHSRpool]

I am testing with Lamotte color q, I realize this test kit is not very accurate but have not decided on which test kit I am going to switch over to.

 

[kimkats]

Look below in my signature to see the two test kits TFP uses and loves! The TF-100 is the best bang for your buck.

Kim

 

[CHSRpool]

Thanks for the info, I like have used the TF-100 and personally like it but the current facility is commercial use and multiple bodies of water must be tested many times a day. As for the chlorine problem I shocked with 6 gallons of bleach overnight and it finally started holding chlorine today. Must be a build up of organics or something but nothing visual to note.

 

[tim5055]

Thanks for the info, I like have used the TF-100 and personally like it but the current facility is commercial use and multiple bodies of water must be tested many times a day. As for the chlorine problem I shocked with 6 gallons of bleach overnight and it finally started holding chlorine today. Must be a build up of organics or something but nothing visual to note.

Please do not confuse the ease of use and specificity of testing data provided by sensor based testing with the accuracy of drop based testing with Taylor reagents. If you do choose to go with sensor testing I would recommend comparison testing with drop based reagents on a regular basis.

As to the chlorine issues, I would recommend an OCLT to prove that the organics have been eliminated. A single night of "shock" generally will not clean it up.

 

[chem geek]

According to Arkansas state pool codes:

SECTION VI. WATER.
:
B. Pool Water Quality.
:
4. Testing and Sampling of Pool Water. Chemical water quality testing shall be conducted by the pool operator at such intervals as required by the Department. Water chemistry tests will also be made by an authorized employee of the Department at the time of inspection. This does not preclude a facility from utilizing testing facilities provided by a pool service company.
:
:
SECTION XVI. TESTING EQUIPMENT.

All pools/spas shall have a functional and accurate test kit or equipment for measuring free and combined chlorine or bromine concentration, pH, total alkalinity and cyanuric acid (if stabilizer is used in pool/spa water).

Other test kits may be required when deemed necessary by the Department. The use of orthotolodine (OTO) tests for chlorine is prohibited. N,N-diethyl-p-phenylenediamine (DPD) test kits shall be provided and capable of measuring the minimum and maximum allowable ranges for chemical operational parameters in Appendix B.

Appendix B lists a min/max for pools of 1.0 to 5.0 ppm (min 1.5 ppm when CYA is used). DPD test kits work with that range and of course FAS-DPD test kits do as well. The required testing interval in the code is daily. However, in high bather-load pools the chlorine level can change more rapidly and some states require testing every 2 hours in that situation. The code says "NOTE: The number of “Daily” testing intervals will vary based on type of facility, hours of operation, & bather load."

 

[ozdiver]

chem geek, that would help him if he were in Arkansas, problem is he is in Alaska.
Hence the large indoor pool.

 

[chem geek]

Obviously I don't know my 2-letter state codes! (thinking AK was for Arkansas instead of Alaska -- Arkansas is AR). OK, so Alaska has /doc/{@1}/hits_only?firsthit]this state code (see also this document which says the following with regard to testing:

18 AAC 30.540. Disinfection
(d) Appropriate test equipment in good repair, with necessary reagents, must be used to measure pool water pH, free and combined disinfectants, alkalinity, total dissolved solids, and hardness. Test kits must meet the minimum range and accuracy as set out on Table D of this section.
:
TABLE D

TEST KIT REQUIREMENTS

MINIMUM MINIMUM

CHEMICAL TEST RANGE ACCURACY

Free available chlorine 0.3 - 5.0 mg/l 0.2 mg/l

Total chlorine 0.3 - 5.0 mg/l 0.2 mg/l
:
(5) the frequency and results of pH and disinfectant tests; pH and disinfectant tests must be made two or more times daily, depending upon chlorine demand;

So that accuracy pretty much means either a FAS-DPD test kit or a DPD test with electronic colorimetric reading.