WH PVC vent pipes can be used only with power-vent /exhaust motor equipped hot water heaters also known as an induced draft gas water heaters (also CPVC and ABS but some manufacturer and local restriction may apply to all 3 types).
Improper house gas water heater venting could be hazardous for you. Have a look at the pictures, and get it right, get it now – it’s easy and it can save your life.