"Chlorine" smell only while SWG running

[map121]

My pool is about six weeks old and the SWG was installed last week. I notice a distinct public-pool-like "chlorine" smell while the SWG is chlorinating and little bubbles are coming out of the returns. I know this smell indicates combined chlorine, but the Taylor FAS-DPD test shows no combined chlorine and the pool water itself doesn't have a smell. The water is clear and the free chlorine level isn't dropping overnight.

Is this a normal smell while a SWG is running?

Thanks!

 

[JoyfulNoise]

It’s undissolved chlorine gas coming out with the hydrogen bubbles. How far away is your SWG from the pool returns? How fast are you running your variable speed pump while the SWG is making chlorine?

 

[map121]

Okay that makes sense. There's about 50 feet of pipe between the SWG and the returns. I've been running the pump at 1725rpm, which shows 25 GPM on the FlowVis flowmeter.

 

[JoyfulNoise]

Okay that makes sense. There's about 50 feet of pipe between the SWG and the returns. I've been running the pump at 1725rpm, which shows 25 GPM on the FlowVis flowmeter.

50ft of 2” diameter pipe holds about 8 gallons of water. At that flow rate, chlorine gas only has about 20secs to dissolve before hitting your returns. That should be sufficient for most of that chlorine produced but perhaps some is getting entrained by the hydrogen gas bubbles and coming out of the returns.

Are you measuring a strong rise in pH with the SWG running? In a short-pipe effect where chlorine gas can escape rather than dissolve, pH will rise faster than normal. Sometimes that’s noticeable/measurable if you’re looking for it or you might notice you need to add acid more frequently.

You could try running your pump a little slower to see if that helps OR you turn down the duty cycle (output %) of the SWG to see if that helps.