:I have a problem with gurgling sounds coming from the waste pipe of a bathroom wash-hand basin when the water is emptying. the noise goes on for about 20 seconds after the water has drained. cold water makes more noise then hot water. the pedestal trap has a screw type valve which is i presume for releasing air locks. could this be the problem ? the water is not slow to drain away so i don't think there is a blockage.