http://www.watts.com/pdf/F-sbn.pdf

Bottom line: When there's a drop in pressure in a city water system, all kinds of bad stuff may be siphoned into the system through you're neighbor's plumbing.

Case studies begin on page 6. Best not read before lunch.

Lots of focus on how the proper backflow preventer (which the company sells) could have prevented the incidents. Unfortunately, there's not much you can to to protect yourself from everybody else.

The company that published said PDF wants people to buy backflow valves, which they happen to make/sell. I'd take what's said with a big chunk of salt.

Anti-back-flow, anti-siphon, valves are required by plumbing code in many areas.

The local authority would like to have them on all residential lines but so far, largely due to cost and the objections of the home-builder's lobby, they have been limited to commercial properties. Near about every strip mall you drive by you can spot an above-ground turn-off and anti-siphon valve assembly tucked in the shrubs somewhere.

Of course such regulations are bait for the 'government can do no good' crowd and is often characterized as 'the jack boot of tyrannical government on the neck of free enterprise and the common man' but I really don't think they have a case. Yes, someone will sell you the valve and installation and, like true capitalist, make a profit doing so. Then again, if you consider the cost of contaminated water on just one person you can pay for a whole lot of valves.

Contaminated water isn't really much of an issue for most adults but it can be fatal to the very young, the very old, and immune compromised persons. It can, and does, kill infants and old people. Even if they live without any permanent disability the hospital costs can be in the hundreds of thousands.

The price of freedom is responsibility. If you wish to enjoy the benefits of collective, municipal, water supply (tasty, cheap, safe water) you have to comply with rules designed to keep the people using the same supply safe.

Gotta remember to put my Olbermannometer in a faraday cage when reading Art's posts lately. That's the third one I've overloaded this week.

Only you, my friend, can turn a thread about plumbing into something about the bourgeois impurifying our collective boldily fluids and poisoning the little children and seasoned citizens.

I, too, tire of the persistence of a few common themes that seem to be able to infect any topic, including "its always a good time to talk about how unprepared the majority of Americans are". The theme Art brings up in paragraph 3 seems to be particularly out of place on this board.

But I didn't find Art's comments to be offensive. Just a bit of a re-run. Many of Art's other comments and ideas are well received.

I hope that the discussion doesn't get hijacked, because that third paragraph is a really dull, overworked theme.

Our municipal water company has mandated its customers to allow them to install back-flow preventers beginning several years ago. No additional cost to us; its safe to assume it was built into the water bill. Water company employees did all the work.

If you lived in, say, Haiti, perhaps substituting "Typhoid Fever" for "salt" would make sense.

Haiti has no codes on building. It's a real issue if US rebuilding grants should require it (since Haiti has no codes there are no inspectors, so compliance is not a minor issue).

There are plenty of areas (and builders) in the US I'd be highly suspicious of: I wonder how often code inspectors actually check to see if backflow prevention is working?

backflow preventers ought to be required on new housing. they are fairly cheap to add to a new building or one undergoing major remodeling.

Like other safety issues, it's a balancing act between cost and safety.

Unfortunately, many times the building codes are used to make a profit for someone selling something they would not otherwise have a market for and the safety aspects are at best dubious.