Gulley Traps 1

[mechanical3010]

Before the waste pipes exiting from a building are connected to a manhole, why is a gulley trap required, especially when all the fixtures are provided with p-traps that prevent sewer gases from finding their way into occupied spaces? Does the gulley trap amount to a double p-trap which violates the codes? Is such kind of double P-Trapping acceptable?

 

[bimr]

One must assume that you are in the UK.

If you do not have the indoor traps, then you will have air or sewer gas entering the building through the sewer system. Normally, the sewer will vent through the house main sewer stack.

http://www.substruck.ie/our-services/drain-services/diy-guide-to-drain-inspection

In the United Staes, gulley traps are no longer used for sanitary wastes.

Sanitary wastewater is piped separately from storm water so that the municipality does not have treat the storm water. Storm water is discharged separately to streams without treatment. Basically, you do not want to dilute the sanitary waste water with storm water.