Chlorine racing up

[Bazzer87]

Hi all,
Just bought a new house with a pool in Cairns, Queensland. I have a Clear Choice Labs test kit.

Pool is 28000 litre, pebblecrete with a Waterco SWG.

28th June FC was 10.4 so I turned the chlorine production to low.

6th July it was 7.5 so I turned the SWG off.

11th July FC was 4.5. I then turned the SWG to medium setting and on between 10am and 3pm (5 hours/day).

Today the 17th July FC has shot up to 16!

Does this seem right? My old pool couldn't produce that much chlorine if I let it run 24/7. I did add other chemicals between those dates but I don't think they'd effect FC? I added the CYA once the FC was at 4.5, I probably added a bit too much.

Here's my other water chemistry stats.

6/07/22
CYA = 30
FC = 7.5
Ph = 7.8
TA = 60
Ch = 300
Salt = 4800

17/07/22
CYA = 90
FC =16
PH = 7.8
TA = 80
CH = 400
Salt = 5500

 

[Texas Splash]

Welcome to TFP! That's quite the increase for an SWG for just a few hours per day. But your CYA was low before for a salt pool and it's very likely the sun was stealing a good amount of your FC earlier. Then you increased the CYA, a little too much perhaps, which probably helped save the FC being generated. I'm not familiar with that model SWG, but around here if there's a problem with an SWG. it's usually because it's not generating enough. Sounds like you have a work horse of an SWG.

 

[mgtfp]

With CYA 90, you can still safely swim at FC 16, anything up to SLAM -FC according to the FC/CYA Levels is safe to swim in.

Due to the better UV protection at the increased CYA level, your FC shot up, but not badly. Turn your SWG down until FC starts drifting down. Once it gets towards 10ppm, turn it slightly higher again and try to stabilise FC around 10ppm for now. Once you understand how the FC levels react to SWG settings, UV-load, bather-load, etc, you may try to let FC further down towards the SWG-target in the FC/CYA Levels. But I personally think that 10ppm should be a pretty good value for CYA 90 in the tropical climate you are in.

Try hard not to let slip FC too low. You don't want to risk algae. Getting rid of that at CYA 90 would require a SLAM-FC of 35ppm - you don't want to go there in the tropics.

Towards summer you will have to increase the SWG output as the UV-load will increase. There is a good gov webpage where you can monitor UV:

Ultraviolet radiation index

Use this chart to see how the UV index varies throughout the day at our monitoring sites.

www.arpansa.gov.au

It doesn't have Cairns, but Darwin is probably close enough in lattitude to get an idea how UV changes over the course of the year.

 

[Bazzer87]

With CYA 90, you can still safely swim at FC 16, anything up to SLAM -FC according to the FC/CYA Levels is safe to swim in.

Due to the better UV protection at the increased CYA level, your FC shot up, but not badly. Turn your SWG down until FC starts drifting down. Once it gets towards 10ppm, turn it slightly higher again and try to stabilise FC around 10ppm for now. Once you understand how the FC levels react to SWG settings, UV-load, bather-load, etc, you may try to let FC further down towards the SWG-target in the FC/CYA Levels. But I personally think that 10ppm should be a pretty good value for CYA 90 in the tropical climate you are in.

Try hard not to let slip FC too low. You don't want to risk algae. Getting rid of that at CYA 90 would require a SLAM-FC of 35ppm - you don't want to go there in the tropics.

Towards summer you will have to increase the SWG output as the UV-load will increase. There is a good gov webpage where you can monitor UV:

Ultraviolet radiation index

Use this chart to see how the UV index varies throughout the day at our monitoring sites.

www.arpansa.gov.au

It doesn't have Cairns, but Darwin is probably close enough in lattitude to get an idea how UV changes over the course of the year.

Thank you for that information, that is very helpful.