Faulty Anti Vac Trap ?

3 Mar 2006
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United Kingdom
Have just repaired a leak on a compression 40mm waste elbow(tightened it) which is on a fairly long run of waste pipe (c 18-20m) with minimum fall. Once the leak was fixed, the sink connected would not drain properly.

There is an anti-vac trap on the trap - if this is puhed gently with finger, the sink drains with some water dripping from anti-vac trap.

The waste pipe has been treated with chemical unblocker and now been rodded with a drain snake to ensure no blockage - also if leaking elbow is undone and a flexible waste connector attached and fed into a bucket, the sink drains ok.

Is it likely that the anti-vac mechanism is simply faulty ? and the leak itself (which would let air into the piperun as well as water out) was allowing the water to drain ok before .

Or would a more expensive solution be to fit a Macerator pump? Any suggestions appreciated
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