Backflow Preventers for Homes

[Recyclersteve]

I was just listening to a man on late night radio saying one thing that lots of preppers don't have which they should have is a backflow preventer (plumbing device) for their homes. Without one, if the power was out for an extended amount of time, you might turn on your water only to get sludge from your neighbors. Maybe you wouldn't even have to turn on the water- maybe it would just come leaking out of the pipes- I wasn't sure about this part. Nonetheless, this backflow event could present a toxic situation for you.

I do remember hearing in a presentation years ago (I was in the construction industry at the time) that if, for instance, you were in the same neighborhood where firefighters were battling a blaze, their demand for water pressure could create a backflow situation. Without a backflow preventer, you could turn on the shower (not even knowing there was a fire in your area) and have sewer water come out. Yikes!

Backflow preventers are not too expensive- the man on the radio made it sound like perhaps $200-300 installed would be a reasonable price for one for a typical home. The host of the show said he got a deal with a plumber (maybe he was already having other work done or something like that) and got one installed for just $75.

Does anyone here have a backflow preventer or know anything about this subject?

[Recyclersteve]

It appears this is a more complicated subject than I thought it was. Check out the following link from someone who is very much against the backflow preventers for a number of reasons. For instance, he doesn't like the fact that they don't last very long, need regular maintenance, can be stolen, make it easier for an intruder to poison your water supply, etc. Here is the link:

http://www.suncitydave.info/reasons/

[johnbrickner]

Ok, I tape athlete's stinking feet for a living so I'm no expert. I know engineers are supposed to be smart people and I've seen a lot of poorly engineered things in my life but, what kind of idiot would have their sewage system hooked up to their fresh water system in any way, shape or form?

Now, might shat back up the sewer system for any reason? Sure, but thru your fresh water system? All I know is I can look out my front door and see the water tank for my neighborhood up the street about 100 feet elevation or so above my head. maybe more. You can shut down the electric pumps and I'm still going to have positive water pressure 'till that puppy runs dry. At which time, nothing will come out. Nothing.

I'm going to put that backflow preventer right next to my left handed smoke shifter. Could I be wrong? Maybe. But if I am, I know a city engineer that's going to get a ear full.

[68Camaro]

Depends on the system, but most freshwater systems aren't leak-proof - and many, especially older ones, leak like a sieve, and if the pumps don't maintain continuous positive pressure in the system then the groundwater will invade into the system and move upstream from there. That's why when the pumps fail they put out a boil water alert for 24 hours (or whatever) and then tell everyone to run their water so that the system will flush out.

Backflow preventers at the individual level (you can see large ones in distribution systems - they are required) are usually only used (and they are required by code) when a well is used for both drinking or irrigation, or when an irrigation system is fed from a fresh water system. If the ground water is contaminated and makes its way back up the line into the freshwater path then you'll find yourself drinking squirrel poop, or worse.

[fasteddy]

I have installed backflow preventers before but not on a residence...it is my understanding if one was to loose pressure and actually develop a vacuum you could potentionally contaminate the water system with what ever crud you have in your home water system. For instance, your pest control operator uses your water hose to make the pest spray. Instead of an air gap they place the water hose into the tank with the end of the hose submerged in the solution. Then for some reason the water pressure drops and the pest solution backflows into the water system now contaminating it....what a mess that will be financially also. The backflow preventer would prevent this from occurring.

[68Camaro]

New construction here requires individual backflow prevention on each external hose bib.

[Recyclersteve]

That's why when the pumps fail they put out a boil water alert for 24 hours (or whatever) and then tell everyone to run their water so that the system will flush out..

Did you really need to say "flush"? My gag reflex just kicked in!

[natsb88]

Backflow preventers on your water supply don't stop contaminated water from entering your home. They stop water that has entered your home (and potentially become contaminated) from flowing backward into the municipal water system in the event the municipal water system loses pressure (or something odd happens that causes a pressure spike in your home higher than the pressure of the fresh water in the municipal system). Most residential backflow preventers are basically two check valves.

A backflow preventer on a sewer line that connects to a municipal sewage system is what can prevent waste from backing up into your home in the event a flood, downpour, snow melt, failed lift pump, or blockage in the sewer under the street causes a sewage backup. The simplest version is a box with a flapper like a check valve. It needs to be inspected/cleaned regularly to make sure no debris is preventing the flapper from closing. There are also more complex but more reliable gate style backflow preventers that work on air pressure. In my case, my house utilizes a grinder pump with a 1-1/4" discharge that pumps it uphill half a block to the sewer main, so I'm just using a quality (all stainless) check valve as a backflow preventer.

[Recyclersteve]

Wow- good info. Thanks Nate.