Bath overflow drains slowly.

[adamex]

Hello, I stumbled across a problem with my new overflow installed few days back. Overflow and click clack below on photo:

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• adamex
• 30 Apr 2015
• 1

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The problem is that overflow does not drain fast enough and bath will overfill. I can clearly hear water going into overflow but seems to be too slow. When I press main waste and then close it again, then overflow will flow much faster.
Is this normal?

Never tested overflow before so not sure, thank you for all your help.

 

[Hugh Jaleak]

You have there a piece of 3/4" approx diameter pipe, with a pair of 3/4" taps feeding the bath. Both taps running at a decent rate and the overflow is never going to cope. I suspect opening the waste is inducing syphonage in the waste pipe, so in effect the overflow is then sucking the water out the bath, so will take it at a faster rate until the vacuum effect is lost again.

Bear in mind the overflow is only a stopgap to try and limit damage, it was never designed to act as a drain.

 

[cjard]

Hj is right, under normal conditions the overflow water has to exert enough pressure to overcome the desire of the u bend water to stay static in the u. Air in the overflow pipe coupled with a possible restriction from the inlet means it can't easily do this. Opening the waste for a second starts the main pipe flow which can overcome the water sitting in the u and this does indeed start a siphon which sucks the water out of the bath via the overflow. The same happens on our works sink, where some nugget has installed 2 u bends I a row, the later one much larger than the early one. The sink drains very slowly as a result as one is essentially waiting for a trickle of water out of one u to fight against trapped air pressure between the two u bends and push water out of the second