Help! The Plastic on Top of My Water Heater is Melting

If the plastic trim pieces at the top of your water heater show signs of melting the exhaust from the water heater may be backdrafting…and that’s dangerous. Backdrafting occurs when hot exhaust gases (carbon monoxide) spill out into the room instead of going up the vent piping and out to the open atmosphere. The plastic around the hot and cold pipes are just trim pieces and don’t serve any mechanical purpose. But (by design or by chance) they do help our Technicians know if there is an exhaust issue. 

The basic types of water heaters are tank style and tankless style. We’re just talking about tank-style water heaters that are gas-fueled. More specifically, we’re looking at atmospheric- vented heaters (versus power-vented heaters). 

Atmospherically vented water heaters use gravity to move the poisonous carbon monoxide gases out of the home. Because the hot exhaust gas is lighter than the surrounding air it will rise up through the venting pipe or chimney and exit the house. However, it is important that the gasses can naturally rise up and not have to “fight” against obstructions. There are a number of factors we consider when installing a water heater such as vent gas pipe sizing, vertical and horizontal distance, pitch and rise off the top of the water heater. Any of these factors, if not correct, could prevent the gasses from naturally moving up and out of the house. 

As a side note, this is why only licensed plumbers should be installing water heaters. They can be very dangerous to life and property and proper training is critical to installing them safely. Think about it…natural gas, carbon monoxide, potentially explosive-level pressures in a sealed steel tank…what could go wrong? A lot! 

Because carbon monoxide can kill we always inspect the condition of the plastic trim on top of any gas-fueled, atmospheric vent water heater. If you notice yours are melted we strongly recommend you call us to have your exhaust piping checked. Our Technician will provide some options to correct the issue and may also recommend you install a carbon monoxide detector nearby.