Low chlorine level with Salt Water System

[anders73]

Hi
I can not seem to maintain an adequate chlorine level in my salt water pool. I have a brand new in-ground liner pool with a salt water chlorine generator. The details are as follows:

In Ground
30'000 Gallons
Pool Pilot Digital Nano
Ozonator
82 degrees Fahrenheit
Free Chlorine 0
Total Chlorine 0
Combined Chlorine 0
Alkalinity 57 (I know this is low and i am adjusting it today)
Ph 7.3
CYA 79 (I am keeping this high per the manufacturers recommendation)
Calcium Hardness 382
Salt 3200

Everything should be ok, but I cant get the chlorine level up. I have shocked the pool several times and then its OK for a few days before it goes down again. The pool is in full sunlight for about 6-8 hours per day.

Is there something wrong with my salt water system?

Thanks you for any help / input.

Anders73

[PoolDoc]

Hi Anders;

I see several possible issues.

#1 - Your test result numbers suggest they came from a digital 'guess-strip' reader. These readers generate more digits than they actually read. In particular, most 'guess-strip' readers can't reliably distinguish pool water with 80ppm CYA from water with 35 ppm CYA. Essentially, your numbers tell me that we do not know what your pool test results are. They may be (by accident) nearly correct, or they may be far off. In your case, the CYA reading is the one that's most likely to be in serious error . . . and that's the result most relevant to your current problem.

You may want to consider getting a Taylor K2006 kit (Amazon link below), or another FAS-DPD drops based kit. (LaMotte makes one, but it's MUCH more expensive.)

#2 - Ozone and chlorine destroy each other. Fortunately, most ozone units sold in the US do not make enough ozone to have ANY effect on your pool, much less destroy your chlorine. But yours may be an exception. However, what most US ozone units do accomplish is sufficient aeration of your pool to strip carbonate alkalinity. You can find more complete explanations here:
ozone-as-a-swimming-pool-sanitizer.html (http://www.poolsolutions.com/tips/ozone-as-a-swimming-pool-sanitizer.html)
and here
lowering-swimming-pool-alkalinity-step-by-step.html (http://www.poolsolutions.com/gd/lowering-swimming-pool-alkalinity-step-by-step.html)

Till you've got your problem resolved, it might be best to turn off the ozone unit, and close the air intake, or ozone feed line.

#3 - Finally, once you get the K2006, you can check your SWCG output by comparing the FC level of a sample taken away from the pool inlet, with one taken just in front of the inlet WHEN THE SWCG HAS BEEN OWN FOR THE LAST 15 MINUTES. Consumer 'guess-strips' are NOT accurate enough for this.

There are other, Pool Pilot specific, possible issues that may exist as well.

[Poolsean]

How many hours per day is your pump running?

[anders73]

Thanks for your help. I will definitely get the test kit to make sure the CYA level is correct. (it should be at or above 80 for SWCG right?) . The test numbers i posted was from the local pool store, is it typical that they are not reliable? I have been to two different pool stores and they always seem to give me conflicting advice. One says keep the CYA at 80 , the other one says 30 is fine????

Thanks for your help.

Anders73

[aylad]

It is typical that the pool store testing isn't reliable--that's why we strongly recommend getting your own kit. As for how high to keep the CYA, you need to check the manual with your particular unit, but I haven't heard of any SWCG that suggests a CYA as low as 30.

Janet