The reason why you have to raise your water heater is to prevent fires. In the San Francisco Bay Area, and also along the Peninsula, there are plumbing standards that you have to comply with in order ensure your own safety. This is why many municipalities have safety codes that you may not understand, but at George Salet Plumbing we do. This is why you should talk to an experienced local plumber about why you should do things like raise your water heater when you install it.
A water heater installation is a great example for the reason why a consumer or a do-it-yourselfer needs to understand local building codes as well as the reasons why they are put in place. Gas powered water heaters are especially at risk if they are not installed properly.
Many people on the Peninsula and also around the Bay Area have gas water heaters because they are energy efficient. However, they also have to be aware of how to install them. If you have a gas water heater, it will also have a pilot light. Depending on where your gas powered water heater is located, it could actually explode if flammable liquids like household cleaners and gasoline are spilled around it. The pilot light from your water heater is the flame that will ignite the fumes from any spilled flammable liquids.
If your water heater is NOT a flammable vapor ignition resistance water heater, it must be raised to 18 inches if it is located in the garage where a car would be parked. In some of the cities on the Peninsula and in the Bay Area, you may install a flammable vapor ignition resistance water heater on the ground in a garage. However, even with this kind of water heater, you can save a lot of money because when a water heater is raised. This is because you don't have to clean as many contaminants out of the filters and vents.