- Mar 5, 2020
- 3,081
- Pool Size
- 66000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Astral Viron V35
thanks for the links - so on the app if I read correctly - if my output in 24 hrs is 3.6, running at 60% for 8 hours say a target of FC 4. I need to run pump for 2.75 hours at 60% . Is that right ? Is that additional or only ? Big difference ...
You have to create enough chlorine to replace the chlorine you are loosing throughout the day by UV-decay and by bather load (assuming no other chlorine eaters like algae).
EDIT: And if you want to get to a higher level and stay there, then you have to create what's required for that increase plus the expected dayly losses. Usually it's easier to adjust the level by adding liquid chlorine, and use the SWG only to maintain the target. END-EDIT
UV-loss is a percentage of the FC-level. For me in Melbourne with a CYA of 80ppm, it's ( depending on time of year and cloud coverage), up to about 20%. So, if my FC was 6ppm, I'd loose about 1.2ppm per day to UV. For you on Brisbane, it might be more like 25%, and with your lower CYA even more.
FC-loss by bathers depends on the number of swimmers and the time they're in. All the sweat and other body fluids will get oxidized by chlorine. With higher chlorine that will go faster, but the absolute loss is not depending on the FC level - in the worst case until all chlorine has been used.
I run my FC a bit higher, around 8-9ppm to have more leeway, and on a day with no swimming, I might have to generate about 1.5ppm to keep FC constant, with my son having a couple of friends over it might be more like 2-3ppm.
With your chlorinator and your pool volume (and your current 60% setting), I had to run the SWG for 3.25 hours on a day with 1.5ppm usage, or 6.5 hours on a day with 3ppm usage.
In practice, I set my SWG somewhere in the middle to ensure that that my FC stays over the course of a week more or less constant. That's why I like to keep my FC a bit higher to have some buffer for the days when I need more. If after 2 days like that, my FC went down to let's say 5ppm, then I will loose less chlorine the next day (because 20% of 5ppm is less than 20% of 8ppm), so it will get higher again. Should there be no swimmers at all, FC will creep up a bit, but then the UV loss will get smaller (I just edited that, I first wrote higher which is wrong), so the creep will slow down. If I get get a cloudy weather streak, or a very sunny week with lots of swimmers, I might have to adjust a bit. But hey, it's Melbourne, I usually get all 4 seasons within a week, and working on an average seems to work well for me.
Most important is to never ever let your FC dip below the min for your CYA, or you will risk an algae bloom. On the high side, you can safely swim up to SLAM level. It makes no sense to regularly target such high levels, as your UV-losses will be unnecessarily high, your SWG had to work harder and consequently have a reduced life time. But apart from that, there's no problem with swimming at SLAM-FC.
But there a problems with letting FC drop below min-FC: You risk an algae bloom, which will dramatically increase your FC-usage, letting FC drop down to 0ppm, which means that bacteria won't be killed anymore, and the pool will eventually turn bright green.
Therefore, find a target that works for you. Usually it's best to get to your target by adding liquid chlorine (amount to be calculated with PoolMath), and then maintain the daily losses with your SWG.
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