My plumber assured me that a vent made of 4" PVC running out through the roof would be sufficient to vent a tankless hot water heater and a furnace in my 1700 square foot home. The plumber has since disappeared and I'm having a bit of trouble finding a suitable tankless heater. The heater will service a standard kitchen and 2.5 bathrooms, one of which will have a pretty nice shower (body sprays, hand wand, large capacity shower head). My question are, will PVC be a sufficient material to use as a vent and does anyone know of a water heater which can share a 4" vent with the furnace ?
Thanks, Curt