Gurgling sink waste

[rebuilder]

A sink with a waste disposer and normal 1.5" trap fitted. The sink has a vented overflow. The 1.5" waste run runs about 6 foot to a corner and then about 10 foot to the main 4" stack. The stack is vented. The waste pipe runs down all the way. When water is emptied in the sink at the end of the water flowing away a gurgling noise is heard.

Does anyone know how this noise is suppressed ?

Comments appreciated

 

[Hugh Jaleak]

Fit an antisyphon trap in place of the existing trap. The gurgling is caused by the waste pipe running full bore and sucking the water out from the trap when the sink empties.