Water not going down drain - but drain is not blocked

[planemad]

I have a really weird one gents.

I have a new sink installed in my little industrial unit, using new 4 inch pipe connected to the main drain the sink joins this via a boss using 40mm pipe with P trap.
The sink is industrial and does not have an overflow.

When I discharge a sink of water from the sink it drains for a little and then stops and holds water.
I have inspected all the 40mm pipe work and its not blocked, I have also poured many litres of water down the 4" pipe and the water goes away perfectly so my problem seems to be between the sink discharge and the 4" pipe (this run is 30cm max and is not blocked).

Also I have noticed that sometimes when I empty water it goes away but at the end lots of air bubbles come up from the water.

Any Advise gents?

Thanks

 

[electronicsuk]

Does the 4" pipe have any form of vent or air admittance valve?

 

[Nige F]

Not that wierd there was another post like it a while back . There is probably a trapped gulley under the large down pipe

 

[jackecole]

is the fall from the sink to the stack OK? does the trap fall continuously and not rise up again at all??

 

[martyheat]

Hi there

its not to much of a problem just change the waste trap for one with an air admittance valve fitted on the trap

martyheat

 

[Boilerman2]

if the fall on the 4" is not correct it could create enough resistance to stop the sink from draining, check for air admittance and importantly correct fall

 

[tamz]

Hi there

its not to much of a problem just change the waste trap for one with an air admittance valve fitted on the trap

martyheat

This is the only correct answer. Electronics picked up on it too. The problem is due to lack of air.

 

[assured heating]

Or the gravity has failed in your part of the country