The History (Evolution) of Water Heaters: Part III

Posted By: Bruce Davis Sr. Maintenance,

Last month’s article was mainly about Temperature and Pressure Relief Valves which have been required on water heaters since 1910. As a result I was asked if the explosions that used to happen ever still happen. Absolutely! An explosion caused by a capped or bad T & P valve happens here in Washington State about every 10 to 20 years. The last time I know about was in the summer of 2001 in Burien. It was in a store in a strip mall, and several people were seriously hurt, but fortunately no one was killed. Three adjoining stores had their front walls blown completely off, and the water heater blew through the roof and landed 460 feet away in a parking lot. Some bricks and chunks of the building landed more than a block away. A King County Fire Chief said (paraphrased) ‘This was not a gas explosion. The pressure relief valve had been capped (because it was dripping) and the tank had been drained of a little water, but the tank built up steam pressure and that caused the explosion.’ So again, as I said last month, proper annual inspections of water heaters by a professional who refuses to cut corners are vital. 

Beginning in the 1970’s and 80’s, the Uniform Plumbing Code and city codes in many states started requiring water heaters to have several safety measures added when installed, in addition to the items we’ve already looked at.

Seismic Strapping

The first was Seismic Strapping, also called Earthquake Strapping. Obviously, a main reason for it is to prevent water or fire damage by a water heater tipping over during a quake, but more fundamentally, when an earthquake hits in a city or suburb, the whole city water system may get shut down for several days or even several weeks. If the water heater is properly strapped, it will remain upright, and the structure will then automatically have a fresh, potable water reservoir available if needed. Generally, there needs to be two straps of at least 24-gauge metal properly secured to an adjacent wall (not secured just to the drywall); one strap in the upper third and one strap in the lower third and neither covering anything that may need to be accessed for service. And although heavy-duty plumber’s tape can work, it isn’t legal in some states. The best choice is an Earthquake Strapping Kit, commercially available on-line and through most retail hardware outlets.

Drainage Pan

If a water heater is located anywhere it could cause water damage in a structure (attic, attic/ceiling assembly, an upper floor, etc.) a watertight pan of corrosion-resistant materials is required in most states. The pan needs to have a drain-line attached, ¾” minimum, that is plumbed properly and goes to an approved location, such as outside the building or a laundry sink. NEVER into a crawlspace.

Fire and Collision Protection

When a water heater is located in a utility area like a garage, special care should be taken.

Fire and Fumes: Water heaters should never be installed near or exposed to flammable vapors or corrosive fumes; nothing should be stored near a water heater that has corrosive fumes or vapors; ever. If it’s not possible or realistic in a given structure and a gas water heater is used, it should be a Direct Vent’ style unit that gets all its combustion air from the outside and not from inside the structure. In places like a residential garage where there may be flammable liquids or vapors, both gas and electric water heaters need to be installed on a platform that raises all burners and possible sources of spark/ignition a minimum of 18” above the floor, unless the water heater is listed as Flammable Vapor Ignition Resistant (F.V.I.R).

Protection from Physical Damage: In areas like residential garages or warehouses where there are vehicles, water heaters need to be protected from damage by a barrier or post of sufficient size, strength, and placement so the unit will be protected. And again, curbs or posts are readily available on-line or from retail hardware outlets.

All the above additions and safeguards for water heaters are relatively recent; within the last 50-years. These are some of the most common safeguards and protections. I hope these articles have been helpful, but they are far from exhaustive. In all cases, situations and installations, the Manufacturer’s Instructions and Local Code needs to be properly applied and followed comprehensively.



 Bruce Davis, Sr. President   Director of Education and Learning  Sales Manager  Licensed Journeyman Plumber, Licensed Electrician, HVAC/R  Electrical Administrator, HVAC/R  Certified WA State C.E.U. Instructor.

Bruce Sr. is President of Day and Nite Plumbing and Heating, a 67-year-old family owned and operated plumbing and heating business in Lynnwood, Washington. Bruce can be contacted at: 


Day and Nite Plumbing and Heating Inc.

6614 13th Ave. W. Lynnwood, WA 98037 800-972-7000