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Attn: Plumbers - Anti-back-flow valve?

BrianGale's picture

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Hi-

In the January 2001 copy of Fine Homebuilding on page 24, a guy has a question about size upgrades on his home plumbing lines. After answering his question, the plumber responding concludes by saying "And don't forget to install an anti-back-flow valve immediately after the main shutoff."

I have no anti-backflow valve in my house- I have a main shutoff, my meter, and then another shutoff. Are anti-backflow valves sometimes built into the meter, are they really necessary, or did somebody oops when they ran city water to my house in 1998...?

Thanks for the info!

(post #159632, reply #1 of 11)

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There's no anti-back-flow valve on the city water service line to on my house, completed 9 months ago and inspected at every step by the city. This might be brand new or a requirement of a different code or of a state or local jurisdiction. More widespread is the requirement to have anti-back-flow valves on outside hose spigots. The concern in both cases is that you could be filling the kiddie pool that your kid pooped in or filling a barrel full of pesticide. If the water company loses pressure, that stuff could get sucked into the system.

The downside of these hose spigots with valves is that you'll have plumbing that is less adaptable. When a water heater goes down, I've temporarily cross-connected to the neighbor's hot water. But with these valves, if I want to do that or heat the my garage before its heating system is in place or thaw some ground, I've got to run hoses to the utility or laundry room through the washer machine hose spigots rather than connect to the outside hot hose spigot. (Or dump the water on the ground instead of recirculating it).

I'd rather have a whole house anti-back-flow valve than one on each hose bib, but I don't know if the first eliminates the requirement for the second. But I wouldn't worry about the lack of one, just keep the garden hose out of toxic wastes when your water company loses pressure. -David

(post #159632, reply #2 of 11)

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b the outside hot hose spigot?????

In Alaska?????

(post #159632, reply #3 of 11)

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It's a psychological thing, man. They don't really get "hot", they just get "not as cold", but calling it hot makes 'em feel better.

Right, Dave? :)

(post #159632, reply #4 of 11)

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I think there is a difference between back flow preventor for a whole house and the anti siphon device of a hose bib.

As best I can tell, the back flow preventor is an increasingly popular code requirement. Problem is they - or at least commonly avalable units - need maintenance - and what home-owner will do that.

(post #159632, reply #5 of 11)

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If you really want to do some additional research on the subject, there is an organization on the subject - the American Backflow Prevention Association. There web site lists a few horror stories about problems with backflow:
http://www.abpa.org/
Some additional links on the subject of backflow prevention:
http://www.usc.edu/dept/fccchr/ccvlib/
there is even a monthly magazine on the subject if you would care to order it:
http://www.dwbp-online.com/

(post #159632, reply #6 of 11)

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JohnD: Yes, a hot hose spigot. Especially in Alaska. Lets you wash the car or the dog with warm or hot water, deice the car windows quickly and, if you run dogs, broth the dogs easily from outside, inside of schlepping 20 gallons of hot water from inside the house. More houses should have them, IMHO. I used 12-inch frost-proof hose bibs so the valve itself is well inside the heated portion of the house. Why build your own house, if not to get it the way you've always thought they should be built? -David

(post #159632, reply #7 of 11)

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Thanks for the input fellas...

(post #159632, reply #8 of 11)

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The back flow valve that they mean is for the sewer line to stop the sewage from back flowing into your house. We use them in all of our houses hear as we have a problem with the sewer lines backing up in heavy rain storms.

(post #159632, reply #9 of 11)

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They now require a backflow preventer on the supply side plumbing in some areas. Here they also require a small expansion tank on the water heater as when the water expands, with a backflow preventer in place, the water has nowhere to go. The idea is that when a main line breaks they don't have to worry as much about contaminated backflow from houses. Doesn't make much sense when you consider that some will fail and never get replaced, and most existing homes have none. I guess the backflow suppliers will be happy. DanT

(post #159632, reply #10 of 11)

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Dan, some of the code changes make good sense, but I think you have seen the light. Manufactures get thier chance to drive the codes when some failure somewhere gives them an opportunity. How many time have you heard "boil water" advisories after a water line break. All that mud gets sucked right in the pipe, yet they say we need bach flow preventers so if we have a break we won't contaminate thier water. go figure.

Dave

(post #159632, reply #11 of 11)

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Hi-

In the January 2001 copy of Fine Homebuilding on page 24, a guy has a question about size upgrades on his home plumbing lines. After answering his question, the plumber responding concludes by saying "And don't forget to install an anti-back-flow valve immediately after the main shutoff."

I have no anti-backflow valve in my house- I have a main shutoff, my meter, and then another shutoff. Are anti-backflow valves sometimes built into the meter, are they really necessary, or did somebody oops when they ran city water to my house in 1998...?

Thanks for the info!