Is my SWG cell worn out?

[8ightiesfan]

The FC level in our pool is dropping, I have the SWG turned up to almost 100% but it cannot keep enough FC in the pool. Over the last 4 days it has gone from 7 down to 4

The pump and SWG are running 10 hours each day
The pool is being used almost every day
There is adequate salt in the pool (3600ppm)
The water is cloudy around the cell when its on
I haven't cleaned the cell for quite a long time, last cleaned in acid probably in April, but it doesn't look like it needs cleaning to me

Is there a way of testing the output of the cell? Should I clean it in acid to see if this helps? Is there anything else I can check or do, or does the cell just need to be replaced? I am not sure how old the cell is as it was here when we moved in. the SWG is definitely producing chlorine it just can't keep up!

 

[mknauss]

Can you post a complete set of test results from your Clear Choice test kit? Also doing an Overnight Chlorine Loss Test would be a good idea.

 

[CRAD_oz]

Hi 8ighties
Is your SWCG a 25g/hr unit?
If so it will output 3.3ppm of FC at 100% in 10hrs wit hb your size pool.
Are you saying it drops from 7 to 4 everyday or over four days?

 

[Jimrahbe]

8<

How old is the cell??

Either your cell is not generating chlorine, or your pool is consuming more chlorine than your cell can generate.

As Marty mentions, the way to tell is to run and OCLT

Do you know how much chlorine your cell is rated to generate per day..

Thanks,

Jim R.

 

[8ightiesfan]

Thanks for the ideas, I will begin with an OCLT and will come back with this.

To answer your questions:

* Yes it is a G25, CRAD_oz what formula do you use to calculate 3.3ppm/hr?
* 7 down to 4 over 3 days with the output at 95% approx (1 day the cover was on all day), I don't turn it to 100% as the dial gets right to the edge of the red zone
* Not sure how old the cell is
* The pool water is very clear with no signs of algae

FC 4
CC 0
pH 7.6
TA 70
CH 400
CYA 80
Salt 3600

Nick

 

[JamesW]

As long as the dial is in the green, it's probably making the amount of chlorine that it is designed to make.

You can check the voltage and current going into the power supply or going to the cell to see how much power is being used.

 

[CRAD_oz]

8ighties
Use "Effects of adding" in Pool Math.
3.3ppm with %100 output, 10hrs running in a 75KL volume pool. (Using a 1.322 lbs/day cell).

 

[8ightiesfan]

Ok here are some results.
Chlorine went up yesterday, pool cover was off all day. went from 4 at 8am to 5 at 6pm on a cloudy day, then down to 4 at 6.25am this morning, so a loss 0f 1 overnight.
I want to repeat the OCLT as I tested not long after the SWCG turned off so would like to test again to confirm the result, though a loss of 1 is considered a pass anyway?
What I am concerned about is that at near 100% output I expect it should be able to keep a lot more FC in the pool than it is, even in summer with increased use. Am I expecting too much from a SWCG? At this rate I will need to occasionally add chlorine manually

 

[mknauss]

Raise the FC to ~10 ppm using liquid chlorine for the OCLT.

 

[JamesW]

The “25” means 25 grams per hour. 25 grams of chlorine gas added to 75,000 liters is 0.33 ppm.

At 10 hours, you should get 3.3 ppm, which should be approximately correct assuming that the pool is clean with no problems.

PoolMath

Discover the calculator behind the perfect pool, PoolMath. Dealing with pools has allowed TFP to become the original authors of the best calculator on the net.

www.troublefreepool.com

 

[8ightiesfan]

Raise the FC to ~10 ppm using liquid chlorine for the OCLT.

Thanks, I will try this. Must it be liquid or is granular ok too (Calcium Hypochlorite with no added CYA)?

 

[mknauss]

You can use cal hypo if you wish. Add, circulate for at least 30 minutes, then test for the OCLT.

 

[ping]

We need the OCLT number and the CYA level.