Hi, I live in malaysia where there are no Pool Supply Stores and advice is extremely limited, so hope someone can provide some help.
I have an inground concrete, tiled, free form pool approx 28,000 US gallons.
The pool perimeter has about 90% of its length with an overflow edge (approx 150 feet) and is raised 9 inches above ground level. There is a concrete gutter drain to the balancing tank.
The balancing tank is approx 4 feet deep and holds over 700 gallons. It is around 50 feet away from the pump room and the suction pipe is 4 inch diameter up to the pump room where it reduces to 2 inch.
The filtration pump is a 2 HP Pentair Whisperflow pumping to a S900 Waterco sand filter. There are 2 vacuum points, one main drain point and the balancing tank connected to this pump. Normally I operate the pool with the main drain valve set about 70% open and the balance tank 100% as it seems to give good circulation and keep the overflow edge nicely wet and the pool clean.
The problem is that every 15 seconds there is a puff of air coming into the pump leaf basket, then a little turbulent water then totally calm (no air) for another 15 seconds. When I fully open all of the valves there is no sign of any air.
The pool is about 1 year old and has done this from the beginning but is now annoying me that I am unable to find any leak or solve the problem.
One further point is that I do get some air rattling from the filter return to the pool but not when its on recirculate. When I release the pressure guage only water comes out - no air.
Any, ideas, help, etc. would be appreciated.