Nige, these AAV's are a bloody nightmare. Folks dont want unsightly stacks or want to save a few quid so do away with the vent. Fine, until there's a problem. Too many are using the sewer as a dustbin, fat, grease, sanitary products, food scraps and those wretched wipes, so in order to try and keep things moving Sewerage providers are operating a programme of planned preventative maintenance, (PPM), where troublesome sections of the network are cleaned on a set frequency to try and prevent problems building up.
We are finding increased issues with toilet blowbacks though now, often where the air pressure created by jetting the main run cannot escape through the laterals as open vent paths are being blocked with AAV's. Then means covers that can be found on laterals have to be lifted and guarded and occupants informed before you can jet anything. If the rules were followed, and the head of the drain was vented as required, I think these blowbacks would be a lot less frequent!
We are finding increased issues with toilet blowbacks though now, often where the air pressure created by jetting the main run cannot escape through the laterals as open vent paths are being blocked with AAV's. Then means covers that can be found on laterals have to be lifted and guarded and occupants informed before you can jet anything. If the rules were followed, and the head of the drain was vented as required, I think these blowbacks would be a lot less frequent!
