Hello again, thanks to you wonderful TFP folk the water chemistry problems I had have been resolved and all as stayed fine... but unfortunately a problem of a rather different nature has now developed. I've read all the threads I can find on air in filter problems but nothing on the crazy situation I seem to now have. This appears to be an air in the filter problem with a difference!
I have one skimmer and shut off valve and duel sumps with a shut off valve prior to the pump inlet.
Everything is working fine when the circulation is running, PSI is good and not even the slightest air bubble appearing in the pump basket or the large sight dome on top of the filter. (Triton 24 inch sand filter) This ONLY effects the filter... not the pump... absolutly no sign of an air bubble in the pump at any stage... whether on or off. Weirdly it can happen within a few minutes, sometimes 15 minutes... and sometimes even at least an hour and a half after filtration has stopped before the problem becomes noticable... and then it slowly begins!
Just the faint sound and feel of water trickling through pipes and out the waste pipe to start with. A few minutes later the tricke sound turns into a very noticeable loud glugging sound and large air bubble appear rising up from the depths of the filter into the dome. It can rapidly increase and the water level in the filter disappears from sight within a minute or two like bath water going down the plug hole! I'm almost certain that the water stops level with the bottom of the waste pipe out of the multiport... the glugging noise stops and all is quiet. Still no sign of air or loss of water in the pump... even the following morning.
On restarting on filtration the pump remains totally full, there is absolutly no drop off in the pump at any time but I'm looking at a filter dome full of air and water jets! I bleed the air off manually from the bleed valve on top of the sight dome and eventually the water rises and everything is going full blast again. If I don't bleed it off it can take ages for the bubbles to stop appearing out of the returns into the pool.
After doing all the usual leak detection checks for a leak on the suction side of the pump including using leak detection spray on solvent joints, making sure everything is very tight... and looking for little spurts of water on switch off.... and finding nothing whatsoever wrong I decided to renew ALL seals and gaskets.
I undid ALL pipe work that's not solvent welded, disconnected the pump and renewed the internal seals, including a new trap gasket! I completly removed the multi-port valve and removed the old spider gasket and cleaned out the channels and fitted a new spider gasket, perimeter top gasket, two handle spindle seals AND fitted a new handle depression spring. I took the dome off and renewed the perimeter gasket and air bleed valve seals. I aqualubed everything! All threaded joints connections were cleaned and refitted with new thread tape and tightened to within an inch of their lives!
In desperation I disconnected the heat sink pipe connections from the in/out header on the side of the Laars Lite2 boiler wondering if they could be letting in air causing some kind of back siphoning. The flange compression gaskets did look a bit hard and brittle so I replaced them. I also undid the metal to plastic heat sink connections at the bottom ends... they seemed fine so just and cleaned them up and lubed them and made sure they were tight.
Everything now looks clean, tight and good.
The problem still exists in the multiport valve 'closed' position but doesn't appear when set for 'circulation' but then of course the filter IS isolated... and I DO get a big air gulp and just a quick spurt of air bubbles out of the returns on 'circulation' mode start up. That's how I'm running at the moment. I turn the filtration off with the filter full and quickly turn the valve to 'circulation' and it just stands there overnight. In the mornings I let it start up on timer with a big gulp and then turn the valve to 'filtration' when I'm up and around.
I've tried running with one each of the skimmer and drain valves in the closed position in turn... but no joy.
Now I dunno what else to try... just wondering if one of those skimmer/drain shut off valves could have a faulty internal seal... (they are the full flow type) but there has been nothing visible from the outside, they both seem dry and the connections are very tight. I've tried everything I can think of... could it be a leaky valve that's not showing itself...
I'm very puzzeled because of the incredibly long time it can sometimes take before it becomes apparent there is a problem... in conjunction with the fact that it CAN happen sometimes within a couple of minutes. Nothing seems to be consistent!
Even if it is an underground leak why can it take so long sometimes for the air in the filter to become noticable? Also how can it get in with the skimmer/drain valves in the closed position?
If anyone has any thoughts or ideas of what I should try next... I would be VERY grateful to hear of any suggestions or ideas anyone can come up with.