are dead end futures a potable water health hazard?

keyote

I ran plumbing for a top floor apt in my house. at the apt ceiling the 1"cold riser terminates with a valved tee vertically and goes about 16' horizontally teeing to the sink, toilet, and laundry terminating at a tankless DHW above the shower dropped ceiling. I then ran the hot back on the same rack also teeing as i went. But then I continued about ten more feet back to the cold riser location where i hope one day to continue them both up to and additional floor that would be built in the future using the same DHW heater for another bath. Its now occurred to me this might be a health hazard to have this dead end of stagnant water. I put the hammer arrestor and future valve right at the end there. in the back of the house is a similar situation except i only needed to put a couple of 18' stubs since future access will be easy.
While Im confessing I should add I installed one of those pex sprinkler systems which was not required or even approved yet but helps me sleep easier. They are designed to also serve as the water distribution system and you pex to the fixtures. Not really into pex for potable so i made it a looped system in 1" pex for the heads but only tied into the toilets and washing machines. I ran a separate 1" pex riser for that its a 4 story house and put in a very expensive zurn 950XLT2 lead free double check valve which since im a tinkocker I was able to get my mech super to give me free. thinking that covered the legionarres issue for the sprink even if it doesnt really tie into the potable potable but what do i know about double check valves im a tinknocker?

Jamie Hall

Generally a dead end pipe isn't a really great idea, but on the other hand it's quite manageable. What I would want, though, is a valve to shut off the unused portion of the pipe -- and leave the valve closed. This is not so much because of a health hazard -- so long as the pipe isn't in use, there isn't one -- but a safety precaution: if a leak develops in that dead end, it's nice to be able to shut it off.

Leaks are a definite possibility in dead ends; one can get corrosion pockets forming which wouldn't be a problem with circulation, but with dead water might be.

When you do decide to activate the line, though, I would be very much inclined to flush it very thoroughly. There may be some bacterial growth in it. There will be substantial heavy metal contamination in the water, even with top quality materials. In fact, if I could figure out how to do it I would probably run some chlorine through it.

What's the problem with PEX and potable water? I use it all the time, and so do a lot of folks.

keyote

@ jamie
Thanks I think im opening that ceiling up and valving it off all I read about this year is legionnaires
re pex potable obviously theres a lot being used so its just my opinion and Im not a ptofessional plumber if that matters to you.
but since you asked.
Its illegal in NYC, When you take it apart theres slime inside. the inside diameter of fittings is smaller than equivalent copper. the parts are hard to find and more expensive. In places like NYC where every square inch is worth a couple thousand dollars you dont have room for the long sweeps needed for turns like suburban homes so youre using as many fittings as copper but you still cant get as tight as you can with copper. despite the evidence im a little worried about the exposure to polyethylene. I like to plan my systems to have extremely short runs usually a tankless DHW heater above the ceiling of a back to back kitchen/ bath; home runs from manifolds defeat the whole energy savings and comfort of that.it seems no matter how many different pex tools I buy i always need another really expensive one on the next job [sprinkler had to be ex pander system]. Im terrified some mouse or rat is going to chew through a radiant line and cause half a million in damages.It really seems like plumbing for farmers and non union hacks.
But thats because Im a union HVAC guy that builds skyscrapers in NYC so all I know is the highest standards in the world. On the other hand it has a place in radiant which i love, and it made the cost/design of my home sprinkler system within reach. If i were building spec houses id use the hell out of it and laugh all the way to the bank.

Jamie Hall

"It [PEX] really seems like plumbing for farmers and non union hacks "

Oh dear. Well, I suppose that's one way to look at it. Oddly, I am a farmer of sorts, and non-union.

I might point out that a flexible pipe, such as PEX, can be of significant value in some types of work, such as the historic preservation work of which I do a great deal. Is that of value? I don't really know. Dismissing it out of hand, as you have done here, is not particularly helpful, however.

keyote

in my other life as an idaho homesteader im a farmer of sorts too and though im union sheetmetal i understand not everyone can or wants that and it probably isnt going to be competitive at the residential level so i was only being cheeky when i said that no offence intended..But i dont consider so called sheetmetal workers that use flex duct to be true craftsmen in my world ductwork is ductwork and it should be able to pass a 6" waterguage test.. however i dont like people who dismiss new technology just because its new. if a thing has a purpose im all for increased productivity. i dont think i dismissed it out of hand in fact im using it for both the sprinkler system and radiant heating in my own house, and like i said if i were building on spec it would be tempting but the reasons i gave against it are valid and why i didnt use it on my water system.Im surprised you like it for restoration much of NYC is 100 year or more and thats my main complaint it wont fit in the tight wall floor cavities.

Jamie Hall

Thank you, and no problem. The reason I like it for restoration is that it can be snaked through odd spaces -- like old chases and what have you -- without disturbing the surface materials. There's usually enough room after the old galvanized (or sometimes lead!) piping has been removed, but commonly one can't get a straight run of pipe in -- but one can get a snake through, and then pull a run of PEX in place.

I'd rather use copper, and do when I can and situations permit. I do not use it, however, where there is a fire hazard (which isn't unusual). It's just not worth it.