Water Heater Strapping
The double-body strap is the system of choice wherever water heater bracing is required. Also, a step-by-step guide to strapping a storage tank heater.
UPC requires water heaters in seismic zones 3 and 4 to be anchored or strapped to resist horizontal displacement due to earthquake motion. The code specifies that strapping must be installed at two locations, within both upper third and lower third of the unit's vertical dimension. The lower strap must be at least four inches above the controls. Jose Carranva, with A. J. Foster Inc. Plumbing of El Cajon, Calif., measures the water heater to make sure the approved strapping kit will be mounted in proper locations. He notes the heights of selected upper and lower strapping positions.
An earthquake is much more likely to cause property damage than to produce injuries or death, and most injuries that do occur come indirectly, as a result of objects or structures breaking or falling. Those of us who live in "earthquake country" are constantly reminded to anchor, brace or support the large objects in our home and work environments, which might fall and injure someone or cause damage. When the ground starts shifting and undulating, even the largest objects become surprisingly mobile.
A typical residential water heater weighs in the neighborhood of 450 to 500 pounds when full. Its narrow profile and relatively high center of gravity can make it quite unstable when shaken. The small feet that support many water heaters have been known to collapse under the stress of seismic motion, potentially further throwing the unit off balance.
Many units are elevated on small platforms, and can dance right off the edge if unbraced, giving them even farther to fall. The resulting excessive movement or tipping of the water heater can cause water and gas lines to rupture, potentially resulting in fire or water damage or even complete destruction to a home that might otherwise have been relatively untouched by the quake.
Two wall studs are located, and the stud centerlines are marked. Cross marks are made on both stud centerlines at selected strap heights (total of four marks)
The point to anchoring a water heater, then, is to protect life and property by preventing fire or water damage that can result if the unit gets thrown about or tipped over. Anchoring the unit to a wall or other secure structure is an inexpensive and usually uncomplicated bit of insurance. At the same time, it is usually advisable to replace rigid gas and water conduits with flexible ones to minimize the risk of even a small tremor breaking a line and causing fire or water damage.
Although usually thought of as an earthquake issue, water heater protection is also a good idea as a general home security measure. Other natural events, such as hurricanes or tornados, can cause structures to move, and even a careless late-night parking bump could be enough to start a garage fire. In the event of any kind of natural disaster or civil defense situation, the water heater is a significant source of critical fresh water that is well worth protecting.
In terms of earthquakes, California and Alaska are the places we tend to think of first in the United States, although other regions are certainly not immune. There has been recent activity in the Northwest, and most people are aware that even the Mississippi River valley has had some of the worst quakes in U.S. history.
In addition to California and Alaska, areas of Nevada, Idaho, Wyoming, Montana, Oregon, Washington and Hawaii also fall under the Uniform Codes' seismic zones 3 and 4, where water heaters are specifically required to be anchored. Portions of Utah, Missouri, Arkansas, Tennessee, Kentucky and even British Columbia and Mexico are also at increased risk of strong quakes.
Four straps are installed into studs at cross marks using lags and flat washers. Free ends of straps now allow the installer to easily secure and adjust tension at front of unit. Free ends of the two top straps are brought across the front of the water heater. One strap may overlap the other.
Most of the states where earthquakes are a concern fall under the jurisdiction of the Uniform Plumbing Code (UPC), which has required water heater bracing or anchoring in some locations since the early 1980s. Initially, the UPC supplied no specifics as to how to accomplish this, or how many anchors to use. Later, between 1992 and 1994, the UPC was revised to require two points of anchorage, in the upper and lower thirds of the heater, which remains true today (2000 UPC 510.5).
Although the UPC does not specifically say that strapping is the only acceptable method, the double body-strap system has become the standard method in California. Because of the availability of low-cost pre-manufactured kits, this approach is becoming universal wherever water heater bracing is required.
The Uniform Building Code (UBC) addresses in more detail the performance requirements for seismic bracing of non-structural components or equipment over 400 pounds. In fact, the UBC was one of the references used by California's Division of the State Architect in setting up the test program for pre-manufactured strapping kits, as discussed below.
Selecting a point near the front centerline of the unit, the two ends are attached using supplied hardware. The excess strap can be folded back or cut away. The top third of the water heater is now properly secured. The bottom third of unit is secured in the same manner. Reminder: lower strapping must be at least four inches above controls.
In earlier years, various methods of anchoring water heaters were used. Some could be effective, while others offered only a false sense of security:
"L" brackets. Anchored at one side to wall studs (or sometimes even to unsupported drywall!) with wood screws, the brackets attached to the water heater skin or top cap with sheet metal screws. Typically, the wood screws are too short to provide acceptable strength for the load, and the water heater skin is much too thin to keep the sheet metal screws from tearing loose during a significant quake.
Plumber's tape. Inexpensive and available everywhere, this has been used as an anchoring material for years. It is available in various gauges and widths, so the strength of the material varies widely. Much of the commonly available p-tape is light gauge and 5/8-inch to 3/4-inch wide. It has a relatively low breaking strength compared to the weight of a shifting 500-pound water heater.
Unless suitably large washers are used when passing sheet metal screws through the p-tape perforations, the screw heads can pull through the material under load. Jurisdictions that allow p-tape to be used typically require a minimum of 24 GA and a width of 3/4 inch to 1 inch. Some jurisdictions now specifically forbid its use at all. The city of Los Angeles does not allow the use of p-tape on installations over 40 gallons.
Pipe nipple brackets. Strapping or brackets grip the pipe nipples at the top of the unit, alone or in combination with a lower strap. Some of these products had wide acceptance for a time; however, they lost favor several years ago, based on belief that earthquake forces could cause the pipes to break.
Ropes, cabling and plastic webbing. Many fabric and plastic materials are attacked by heat, humidity, temperature and light. They may lose strength over the life of the installation, with no clue of the problem until needed. They may burn through or melt in a fire, allowing a tilting water heater to fall to the floor. If the strap or cabling is too narrow, the outside skin of the unit can be damaged during installation or by even a minor quake.
Metal bands. For cost, strength, and durability, wide metal bands have evolved as the general material of choice.
Single strap. This was considered adequate at one time, but may not do a good job of restraining both the rocking motion of the upper part of the water heater and the shifting of the base, which is especially important when the unit is on a stand.
Double strap. The latest UPC requires two anchor locations, and the DSA' s generic instructions also describe a two-strap system. Some pre-manufactured kits have straps that wrap completely around the water heater, while others go from one side to the other - 180 degrees. There is no uniform legislative or code requirement that specifies either type.
The double body strap has become the standard method of choice, whether wrap-around or 180 degrees, with the 180-degree type overwhelmingly preferred by the trade.
Optional caps may be installed to conceal exposed hardware A properly braced and strapped water heater.
Significant legislative and government attention has been paid to water heater bracing in California due to its active fault lines and deadly temblors.
In 1989, California AB 1890 modified the Health and Safety Code (HSC) to require the installation of water heater bracing or strapping on all new or replacement units installed in California after July 1, 1991. In July 1995, SB 304 made another change, extending the requirement to include all existing water heaters, as well as requiring a real estate seller to certify to the buyer that the bracing has been done.
In July 1996, SB 577 clarified that the required bracing of existing units applied to residential water heaters. Significantly, it also added a statement that the minimum standard for the bracing installation is the California Plumbing Code, or legally enacted local codes (HSC 19211(a)).
Besides directing the Public Utilities Commission to initiate a consumer education program through the gas and electric utilities, AB 1890 also brought the Division of the State Architect (DSA) into the picture. The DSA was ordered to create a set of generic instructions to illustrate typical residential water heater installations, which were to be made available to the public. SB 1890 required water heater manufacturers to inform buyers that the unit must be anchored or strapped, and allowed the manufacturer, at its option, to include copies of the DSA's generic instructions as a guideline for consumers.
It is clear that the DSA's instructions are intended to be advisory, and are not intended as the only legal method. In fact, the Health and Safety Code specifically states that these instructions do not supersede local codes (HSC 19216).
The DSA's Certification Program
In addition to publishing the instructions, possibly in response to inquiries from manufacturers, the DSA worked with the utilities and seismic engineers to develop a performance-based certification program by which pre-manufactured restraint products could be evaluated. A standardized test program was established, based on the seismic loading requirements of the UBC.
Manufacturers may test their products using a third-party laboratory and submit the results to the DSA for review. The DSA has developed, and made available to the public, a listing of manufacturers and products certified as valid alternative methods to the generic instructions.
An important condition of this certification is that the manufacturer's instructions must be followed when installing the restraint kit. Local building departments in California now allow DSA-certified kits to be used in place of either the DSA's generic instructions or any other guidelines that the local jurisdiction might provide. In fact, the city of Los Angeles actually requires the use of a DSA-certified double-strap kit on any water heater over 40 gallons.
A DSA-certified pre-manufactured kit is clearly the most practical, cost-effective and certain way of anchoring a water heater in compliance with applicable codes and standards:
- The kits' effectiveness has been demonstrated by lab testing.
- DSA-certified and approved methods are virtually universally preferred.
- Kits contain all necessary parts and instructions.
- Standardized hardware ensures fit and strength.
- The kits' simplified designs allow easier, standardized installation and inspection procedures.
- Straps are typically wider than p-tape, distributing loads over a broader surface.
- They require no load-bearing attachments to the skin of the water heater.
In addition, some kits may:
- Permit adjustment to ensure the best possible fit.
- Contain high-strength hardware to prevent breakage.
Be reused on replacement water heaters.
Photos courtesy of Hubbard Enterprises
"This article was originally posted on ww.reevesjournal.com."