"Bought this trap to replace a McAlpine vented trap which leaked whenever there was a slight blockage in the waste pipework. It is an exact replica and easy to fit because there is no vent in the way of the plastic screw in nut that fits to the basin outlet. Vented traps are intended for use in non-vented systems but otherwise I can see no benefit except that they stop the water gurgling as it leaves the basin."
"I purchased this to replace the same thing that had an air admittance vent built in that had started to vent foul smells. This product is well made, easy to fit and works well, I have used several now and shall steer clear of the one with vent."