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Seismic strapping material


Robert Jones
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While the requirement for seismic strapping states it must be secured at the top and bottom third of the tank, is there anything that states what type of material it must be? Had one today that was strapped in the right area(s), just with rope. They took the time to add 2 boards to strap it to.

Thanks.

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The rule is full-circumference straps in the top and bottom third and the lower strap may not be closer than 4 inches to the top of the controls. I've seen heavy nylong web strap systems designed for this purpose and there is no disputing that they are "straps." I think you'll have a hard time convincing anyone that a piece of rope is a "strap" when it's clearly a rope.

By the way, both of those look like they are closer than four inches to those thermostats; so aren't they technically closer than 4 inches to the "controls."

ONE TEAM - ONE FIGHT!!!

Mike

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While the requirement for seizmic starpping states it must be secured at the top and bottom third of the tank, is there anything that states what type of material it must be? Had one today that was strapped in the right area(s), just with rope. They took the time to add 2 boards to strap it to.

Thanks.

The UPC doesn't specify the material. It just says that the water heater has to be anchored or strapped to resist horizontal displacement due to earthquake motion. It looks to me as if there's a lot of slack in those ropes. What happened when you pushed on the tank?

- Jim Katen, Oregon

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Funny, I can't find any actual code. I have found a few references to using 22-guage 3/4" wide straps for various munis but without any code references. This might be your best bet, from the WA Dept of Health...

Securing Your Water Heater It says to use "heavy-guage metal strapping" but also suggests "commercially available strapping kits" make things easier.

Obviously, the rope is just plain wrong (screw whether the codes say so or not). For the $15-20 a strap kit costs, who is going to argue with you?

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From the Washington State Plumbing Code:

508.2 In seismic design categories C, D, E, and F, water heaters shall be anchored or strapped to resist horizontal displacement due to earthquake motion. Strapping shall be at points within the upper one-third

(1/3) and lower one-third (1/3) of its vertical dimensions. At the lower point, a minimum distance of four (4) inches (102 mm) shall be maintained above the controls with the strapping.

Since it's talking about the "lower point" I think that they mean gas controls. Even so, it just makes sense to keep the straps off of the stat covers.

I see nothing in the requirement that would exclude a rope.

I see nothing in the requirement that requires the strap to be full circumference.

I'd be much more concerned about the quality of the installation than the choice of rope here. Why, exactly, wouldn't a rope work as well as a metal strap if there were an earthquake? Give me a length of decent rope and I can lash down a water heater far more effectively than 90% of the metal strap kits that I see. I'll bet that most any ex-serviceman, trucker, or boy scout could do the same.

- Jim Katen, Oregon

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Jim, if that set-up looked like it had been done by a professional trucker, or even a cub scout recruit, I might agree...but it doesn't. And...what if there's also a fire? Are you comfortable enough with the tensile strength of that particular rope to just recommend better knots?

I don't dispute that the installation in the original picture is inadequate. But that doesn't mean that rope wouldn't work at all.

Fire? Where's the requirement that the strapping survive a fire? If there's a fire, having to replace the earthquake strapping is going to be pretty low on my list of concerns. Heck, you'll probably have to replace the whole water heater.

Tensile strength? How much do you think it'll take to prevent a water heater from being displaced by earthquake motion? I'll bet that rope is way more than strong enough -- if it's tight and the tank doesn't have the opportunity to develop lateral acceleration.

The requirement is painfully simple. There's just no need to elaborate on it. If there's an earthquake that's large enough for this to come into play, the water heater really isn't going to be really high on the list of concerns.

I went through the Loma Prieta quake in San Francisco in '89. A portion of the Bay Bridge collapsed, thousands of houses were shaken off of their foundations, and 63 people were killed. I toured a lot of the damaged areas and most of the water heaters that I saw were ok. I saw dozens and dozens of houses in Oakland that were just fine in most regards, except that they had moved laterally a foot or two and fallen off of their foundations. Many of these houses still had all of their windows intact and still had dishes sitting on the shelves.

Sure, the water heater tanks should be strapped. But it just doesn't make any difference if you use rope or metal. After the earthquake no one is going to care.

- Jim Katen, Oregon

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Sure about that?

This is from one of AO Smith's gas water heater installation manuals:

For California installation this water heater must be braced, anchored, or strapped to avoid falling or moving during an earthquake. See instructions for correct installation procedures. Instructions may be obtained from California Office of the State Architect, 400 P Street, Sacramento, CA 95814.

ONE TEAM - ONE FIGHT!!!

Mike

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Sure about that?

This is from one of AO Smith's gas water heater installation manuals:

For California installation this water heater must be braced, anchored, or strapped to avoid falling or moving during an earthquake. See instructions for correct installation procedures. Instructions may be obtained from California Office of the State Architect, 400 P Street, Sacramento, CA 95814.

ONE TEAM - ONE FIGHT!!!

Mike

The document from California Office of the State Architect is attached.

Download Attachment: .pdf"]icon_adobe.gif waterheaterbracing_11_30_05[1].pdf

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I have not reviewed the document from the Cal Architects board in full however it seems to put an emphasis on properly installed lag bolts (I would assume for pull out resistance). In the photo of the condition from Robert, I cannot see how the cleats are attached. If the rope has slack and the cleats are not adequately anchored does this make it a problem?

If it were me reporting on the condition I would state that it is outside of my ability to evaluate the structural integrity of the installation (or something to that effect), and recommend that either a strapping kit be installed per manufacturers recommendations, or the installation be assessed by a structural engineer. I think we all know that no one will pay for an engineer to do an evaluation, and if an engineer looked at it he would not be able to calculate the moment force applied to the upper rope because of the slack. With that being said do I think it is probably adequate? Yes I do. Would I have it in my own house? No. The strapping kit would be a nice peace of mind insurance policy for me. I would definitely call this in a report as part of my due diligence.

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Sure about that?

This is from one of AO Smith's gas water heater installation manuals:

Quote: For California installation this water heater must be braced, anchored, or strapped to avoid falling or moving during an earthquake. See instructions for correct installation procedures. Instructions may be obtained from California Office of the State Architect, 400 P Street, Sacramento, CA 95814.

Hi Mike,

I admit that I did not see the CA installation note in the instructions that I read. They very well may have been included-- I'll have to go back and re- read more carefully.

Having said that, would you consider the California Office of the State Architect document as something that must be followed in OR and WA? I wish that AO Smith would change their wording to include all areas subject to seismic restraint requirements. Heck, they could even point to the CA document and state that those guidelines must be followed in areas where earthquakes may occur.

I see hokey restraint methods all of the time. I just tell people the intent of them, and let them know that they may or may not work when needed. They can make up their own mind as to whether it should be fixed. I think I'll start adding the CA document to my reports-- someone may actually read it.

Ramon,

Thanks for posting the document.

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