FAQ - Indoor waste systems

Please find the calculation for the air admittance valves here.

PUM makes space for other things in the bathroom cabinet compared to a bottle trap. It works as a mechanical odour trap, using a silicone membrane instead of a water trap. The membrane is always closed, but opens by the flow of water. The PUM also functions as an air admittance valve if there is negative pressure in the drainage system – it opens and lets air in when necessary.

If you already have a bottle trap below your sink you are not able to combine that with PUM. If PUM and a bottle trap are both used, this will reduce the flow drasticly.