Q. Problem With My Water Heater’s Location?

Q. Hey Mark,
I’m in the process of buying a house and just had a home inspection done. One item that the home inspector itemized in the report is the water heater in the garage. He said that it shouldn’t be installed on the floor of the garage. Where else could it be installed? I don’t get it. Every place we’ve lived before had a water heater sitting on the floor.

A. Hey Dorothy,
This is a great question. It sounds like the issue wasn’t explained thoroughly by your inspector. Actually, the problem isn’t that the water heater is on the floor, nor is the problem that the water heater is in the garage. The problem is that the water heater is in the garage AND on the floor.

Here’s why:
When gasoline evaporates (from your stored gas cans, or from drips from your car or lawn mower), it creates a combustible vapor. This vapor is so combustible that the carburetor in your car vaporizes the liquid gas in your engine to make the car move. This gas vapor can and will settle and pool in lower areas until it can naturally ventilate out of the garage. When these vapors collect, any spark or combustion source can ignite them causing an explosion. This is where the problem with your water heater comes in. The water heater’s heat source is at the bottom of the tank, at approximately the same level as that gasoline vapor. Heat Source + Gasoline Vapor = …You do the math.

Most plumbing and building codes require that any water heaters located in garages, either be in a room where the gas vapors cannot gain access to the appliance, or be raised to a level where their combustion chamber is at least 18 inches above the floor.

As an additional note: There are some water heaters that have what is referred to as a “sealed combustion chamber.” These heaters are specifically designed to operate under these conditions and are not required to be elevated. The label on the heater should state if it has a sealed combustion chamber or not.

Mark Nahrgang is the owner of Kingdom Inspection Network Group – St. Louis and is a professional NACHI certified building inspector in the St. Louis metro area. Mark performs home inspections as well as commercial inspections throughout St. Louis and St. Charles County.


One Response

  1. thanks for the answer Mark, I was actually wondering that myself

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