Even a minor earthquake has the potential to topple a water heater that is not properly braced. A broken water supply line can cause major flooding, a broken gas line may result in a fire. Below a typical example of an unsecured gas water heater in a Victoria heritage home.
More often than not water heaters are not braced at all or are braced inadequately. Even though the BC Building Code 2012 requires seismic bracing, the code itself does not go any further than referring to the guidelines of the California Division of the State Architect. Those guidelines are very specific and if followed correctly provide for a secure water heater.
Since replacing a water heater does not require a permit in Victoria, the installation of replacement water heater is not checked by a plumbing inspector. As a result the vast majority of water heaters I see around town are either not braced at all or they are braced completely inadequately. The example below is typical: wrong screws/bolts, wrong method of strapping, wrong size plumbers tape, and the wrong attachment point.
If you would like to compare the installation of your water heater to the guidelines/code check the link:
These guidelines work well when the water heater is in close proximity to a structural wall. Unfortunately gas water heaters, especially in older homes are more often than not adjacent to the chimney to facilitate convenient venting of flue gases and not close to structural walls. Unreinforced masonry which most old chimneys are made off, is not suitable for securing water heaters. Securing a free standing water heater is challenging. There is a commercial free standing water heater brace available from Watts:
This water heater restraint is rather expensive with a cost of up to $ 500.00 Canadian not including installation.
Working with an engineer I have designed a home made version of the Watts free standing water heater design at a fraction of the cost. It provides flexibility for challenging locations where the Watts design may not fit without draining, disconnecting and moving the water heater.
All of the parts are available at local building supply stores. The structure can be bolted to the floor exceeding the requirements of the California Division of the State Architect.
Your water heater can also be a valuable source of clean drinking water after a major earthquake. Making sure it remains upright is important. Equally important is to make sure you have a way of getting to the water. Most water heaters have a drain plug that is close to the bottom of the heater. That makes draining a challenge unless you already have a potable water hose attached to the drain plug.
Using a garden hose, if you manage to find it after an ertahquake is not a good option.
Last but not least consider installing flexible water and gas supply lines.
Well worth the cost and I can refer you to a great plumber/gas fitter to do that work.