To enable the kitchen window to be made wider the soil stack had to be moved sideways. The point of exit from the bathroom however could not, creating a need for studwork boxing to conceal it. To avoid having the top of the soilstack coming through the roof a vent valve was used to cap the soil pipe above the toilet seat line in the bathroom. Located in the ridge of the roof the vent valve was supplied air movement by an inconspicuous white grill in the ceiling