Air getting into filter system

[poconojoe]

Yeah, sorry, I didn't realize PTFE was teflon tape. I am very familiar with teflon tape.
I thought the union was cracked and you repaired it with some kind of tape.
I apologize for not realizing you were talking about sealing the threads and not some kind of crack in the union.

A while back I got tired of the hoses not sealing, just like your situation, including many pin holes, splitting, etc.
Some of those hoses were either too loose or too tight to fit the hose adapters. It was a pain every Spring dealing with reinstalling them. I would wrap rubber (not regular plastic) electrician's tape on the hose adapters to build it up.

I switched it all to PVC. For the places that needed a flexible hose, I used flex PVC. It has a thick wall, mates to all standard PVC fittings and you can even use the same primer and glue as the standard ridgid PVC.

 

[NigelW]

I have had a response from the filter manufacturer as below. I will test things out, and let you know how it works out.

"There are two reasons this might be happening.

Because the outlet end of the hose is underwater this causes an increase in pressure inside the filter.
This will cause the gases present naturally in the water to permeate out.
This is helped by the fact that the weather is now getting warmer which causes the nitrogen and Co2 in the water to permeate.
The air will form in the head of the filter until it gets so much that it whooshes out.
This point can be shown if you take a glass of water taken from a tap and leave it overnight.
In the morning the water will be full of bubbles.
This air entrapment will cause the filter to bypass, and the water will not flow through the foams.
This is part of the design to avoid the filter exploding if it is not cleaned and the foams become totally blocked.
Some people submerge the outlet because they do not like the sound of the water entering the pond.
If the pump is too near the filter the pump will pick up the air and send it back to the filter again increasing the problem.
If this is the case the solution is to move the pump as far away as possible and to consider returning the water above the water surface.
This will also help with oxygenation of the water - (it is not oxygen that you are seeing but more likely nitrogen, Especially in a pond situation where the nitrogen content will be a lot high.

Secondly, there may be an air leak in the diverter valve. This may not result in a water leak due to the venturi effect. If water rushes perpendicularly past a hole then the water does not flow out of the hole but causes a vacuum which in fact sucks air in.

When you use the diverter the leak may not be apparent as the valve needs to be moved to use it. Especially if you have run a length of hose to a drain as the leak may only be small and not easily visible. Try taking the waste hose off whilst the filter is running and listening for any air being sucked in."

 

[NigelW]

One of the possible problems suggested by the manufacturer as above was an air leak in the diverter valve. They sell spares for £10.50 ($13) which seemed like a sensible purchase. Because they were out of stock, they offered me an entire filter lid assembly for £25 ($30) when the normal price is £92 ($112)! Combined with lifting the outlet above the water surface I am hopeful that the problem will be solved.

 

[poconojoe]

Good luck. I hope you figure it out.

It's probably much easier anyway to just switch out the lid than to take apart the diverter assembly.

Let us know how you make out.

 

[NigelW]

Whilst I was waiting for the new lid to arrive, I lifted the outflow above the surface. This obviously prevented volcanic eruptions of bubbles from underwater, but there were a lot of gurgling noises which got quite noisy when they reverberated down the pipe.
I also blanked off the waste outlet with an airtight seal in case it was the valve letting in air. This made no difference.
When the new lid was fitted the effect was instant - smooth flow of water and no noises. I'm very glad that the valves were out of stock, so that they offered me a complete lid at a fraction of normal cost.
I dismantled the old lid, but there was nothing obvious wrong with it. The valve appeared to seal properly. I can only assume that the seal had failed between the inlet and the central column that takes water to the bottom of the filter. This would cause the water to by-pass the filter medium, and could cause a low pressure zone that might draw in air. I couldn't see any problem with the seal, so that is pure supposition. Whatever the problem was, the new lid fixed it, and I got it very cheaply!

 

[JRS]

Thanks for the update. Glad it worked out.