How can my SWG produce 2-3 ppm at cell but only 0.5 ppm come out ?

[cadena]

Hi everyone,

I am trying to determine if there is an issue with my pool since, yesterday, I measured Chlorine in the SWG and I got a reading of about 2-3 ppm. Last week, on Monday, I added salt to my pool since it had almost nothing left and no chlorine was being produced. I set the pump to turn on 2 hours in the morning and 2 hours in the evening but the pool started getting dirtier and maggots starting appearing in the water. Yesterday a friend came over and advised me to leave the pump working for the whole night since 4 hours might not enough to generate the chlorine needed in my pool. I did what he told me and this morning I have found the pool to be much more cleaner (only a few maggots remaining). However, I have just measured now the Chlorine level at the inlet jets and is really, really low. Something like 0.3 or 0.5 ppm. This doesn't make sense to me because if chlorine is being produced at the SWG then why is there so little amount coming out from the jet ? I measured the chlorine level at the far end and I also got the same reading. I set the SWG to 50%, pH is at 7.2 and I have 3 inlet jets. I would really appreciate your help.

 

[wireform]

How are you testing, what are all your chem levels ? You may have been checking the returns when the cell was Cycled off if it's not set to 100%. In any case your FC is way low.

 

[PoolGate]

SWGs work on a cumulative basis. They produce a small amount of chlorine when they are running. Many (most?) people run their variable speed pumps 24x7 and set their SWGs to the appropriate percent to product the 2-3 parts of chlorine they use each day. You cannot measure what comes out of your SWG as an accurate measurement of its daily production capabilities. But off the cuff, 4 hours of runtime is not enough.

 

[mgtfp]

I ran some tests a couple of weeks ago, where I took a sample with a syringe straight out of the return line and compared that with a sample from the deep end. The FC in the sample from the return line was about 3ppm higher than in the sample from the deep end. This seems to make sense with my 25g/h cell, assuming a water flow rate of about 140L/min (25g/h = 416mg/min of Cl₂ in 140L/min of water makes about 3ppm of FC). SWG was running on 100% for that test.

It sounds like in your case, the FC from the return line is the same as in the deep end sample (in both samples 0.5ppm), which means that your SWG is not adding significant amounts of chlorine.

When you say that you measured 2-3ppm in your SWG (I assume that you opened your cell and took a sample from there), does that mean the FC was 2-3ppm higher compared to a sample from the pool, or do you mean 2-3ppm absolute level in the cell?

It sounds to me that yesterday the FC in your pool was 2-3ppm, and today it is 0.5ppm, no matter where you test it. Sounds simply like your SWG is not producing any chlorine.

Is your cell clear, can you see bubbles being created inside?

Make sure to take the sample with a syringe from inside the return line, not just from next to the return line, when trying to work out if your SWG is working, and set it to 100%. This is even more important with SWGs that work on a duty cycle. These types of SWG produce, when set e.g. to 50%, full chlorine output for 50% of the time, and no chlorine at all for the other 50% in the duty cycle. So, when taking a sample at a random time, you would have a 50% chance, that the SWG was off at that time.

It could also be that with the SWG on 50% (in a model that doesn't work on a duty cycle but reduces the output to 50% for 100% of the time), and your 1.5 HP single speed pump, the FC increase in the return water is simply to small to be detectable. Which brings me back to wireform's question: How do you test your chlorine level?