While the contents vary by manufacturer, the Watts model TSE-25 water heater strap kit includes four galvanized straps with the lag bolts necessary for installation held in place by paper keepers. These kits help to secure tanks in the event of an earthquake.
The force of an earthquake is enough to topple some water heaters. The weight of the falling tank has the potential to sever water and gas lines. The damage to the glass-lined tank from the fall is often unrepairable. The severed lines have the potential to cause water damage and start fires. Even though quake damage to some houses is minimal, the resulting fire from a toppled tank can destroy the structure.
Studies of strap failure from previous earthquakes bring improvements in the methods of strapping. Use of metal plumber's tape for strapping is no longer advisable. The kits offer the heavier straps water heaters require to survive during earthquakes. Kits also include the two or more straps the studies show to be most effective when the homeowner installs one at the top and one at the bottom of the tank.
The strapped water heater also provides an emergency source of drinking water in the event the earthquake disables public water supplies. Most tanks hold about 40 gallons of potable water. The drain valve at the bottom of the tank makes this water easily accessible.