Laundry Drainage System Re-route. Here you see a laundry drainage system re-route. This is necessary when the existing drainage piping has lost its integrity and can no longer be cleared or repaired. We used sch.40 PVC pipe and fittings and sealed all exterior penetrations with hydraulic cement. The new sewer was vented using an AAV (air admittance valve). These allow air into the system to allow for proper drainage but protects against sewer gas intrusion. AAV’s are good cost effective ways to vent a new system but may need to be changed out every few years.