Is that visible round plate itself the valve, or is it just a cover and the valve is underneath?
It's spotlessly clean and never even knew I could possibly remove the round plate. I daren't not remove it and I can't see how anyway.
So it's been a couple of weeks since the final OCLT and completion of the SLAM.
Pool has been spotless, wonderfully sparkling water - BUT still losing chlorine!
I just did another OCLT today and yes - the two tests showed a net loss of chlorine.
So, back to square one.
Just to repeat and summarise:
Have had the pool just over two years, newly built.
Up until around November last year, I'd always set the summer SWG generation to around 30% - 40%. Running about 8 to 10 hours a day. And that proved to be to the ideal level to maintain Cl around 3 to 5ppm. It is only a small pool, roughly 22,000 litres.
Always covered with a Abgal pool cover.
Winter time SWG is set to 5% and 8 hours.
Last November, had a minor algae outbreak following a huge windstorm that blew in lots of leaves.
Whacked in a load of chlorine and it cleared up over a few days. Basically a SLAM but without the close monitoring (yeah I know you peeps will say thats not a real SLAM and you need to be monitoring closely, doing OCLT, checking every few hours etc, but when it comes down to it, a SLAM is just a massive dose of chlorine maintained over a few days - which is what I did).
Since then, I can never take my eyes off the pool chem levels.
The chlorinator, even running at 95% over 11 hours cannot maintain a decent chlorine level. If I did that previously the Cl level would be north of 10ppm!
Thinking the SWG was faulty, I had it replaced under warranty. Made no difference.
So a couple of weeks ago I did a proper SLAM. It was a full 3 days. And the final OCLT showed a nil loss overnight. As an aside - I think the first time I cleared up the algae mentioned above I actually used even more chlorine over those few days - so actually the proper SLAM used less chlorine that what I did last Nov.
Now I find I am needing to supplement my SWG with about 500ml to 1 litre of liquid Cl each week. It just seems wrong and not what I have been used to for the past couple of years.
No other chemicals have been added to the water.
[ As an aside, I also discovered from this thread that my constant topping up of CYA is odd too. Apparently it's normal (for everyone else) that CYA is fairly constant once the target level has been reached but that has never been the case for me. I've always needed to top up CYA, so for me that is normal. Case in point - 6 days ago the CYA level was around 55. Measured it just now, it's 30. I'd go through a 2 kg bag over about 6 to 8 weeks. ]
About the only thing I can think of is theres a dead body inside the filter media! Obviously not, but really there's nothing else I haven't checked. Every nook and cranny has been scrubbed, SLAM hasn't made a difference. I use a skimmer sock so only minor debris gets past the sock and into the filter anyway.
Even the pool cover has been thoroughly cleaned as it was also in place during the SLAM, and even bleached a bit.
Methinks I need an expert chemist with a wider range of tests than just is what available to the average punter. Or maybe I need a voodoo shaman. Something is odd and I can't work it out.