I am planning to replace all the old galvanized water supply to a small first floor bathroom over a tight crawl space with copper. Its going to be a bit tough to solder in the crawl space (though probably possible), so I'd like to do as little as possible.

I was thinking of using flexible copper for the horizontal runs through the crawl space (to minimize joints), and then rigid copper for the vertical supplies to the fixtures.

Any suggestions for minimizing the number of solder joints? Should I consider compression or flared joints in the crawl space? Is soldering the only good way to interface between the flexible and rigid copper? My understanding was that within the bathroom walls it was best to stick with soldered connections and rigid pipe.

Is thin-walled copper (M) OK for typical residential usage? My contractor insists that 1/2" supply should be fine for the typical toilet, lav, shower combination .... I had originally thought of 3/4" for cold and 1/2" for hot.

Thanks very much for any feedback !!!

Your best bet is to use PEX! You will be done faster and not burn down the house or injure yourself.

It is my opinion that PEX is far superior to M copper and I even like it over L for many reasons.

Secure you stub outs with quality parts (Eared els and such) and you will have a great installation.

If you don't want to solder, I think Scott is telling you right. I would consider the manifold option, so you won't need individual stops at the fixtures. If you don't manifold, I would use 3/4" for the cold, to the 2nd fixture. It depends on the length of the run if I would use 1/2" for the hot. Undersizing pipe causes higher velocity which can lead to noise and banging pipes.

Thanks very much for the suggestions. I have read enough messages on this board to anticipate that Scott D. would recommend PEX. .... and I do believe you concerning its benefits.

My problem is that I am pretty comfortable with copper, and know nothing about working with PEX. This one small job is pretty much the end of the plumbing work on my house for awhile, and I assume that the investment in PEX tooling would be significant?

I can solder in the crawlspace if necessary (and I think I can avoid burning the house down) .... is my idea of combining flexible and rigid copper reasonable / common ?

Thanks again !

The length of the run is pretty modest .... probably only about 15 feet or so.

My thinking on the 1/2" copper for the hot was the amount of hot water I would "waste" waiting for the water to warm up. The crawlspace is quite cold in the winter (hopefully not freezing, because the radiator pipes run around down there also). With 3/4", wouldn't we wait twice as long for the water to heat up?

Given a 15 foot run, do you think 1/2" copper for the hot would be sufficient - shower and lav?

Sorry brother. I did not mean to offend you with that "burning down the house" comment. Hard to know here who has skills and who just saw it once on TV and now they know everything.

Anyway, if Copper is your thing, go for it, but I really would not use M...ever. As for PEX tools for one job, they (Crimpers)are rented out may places pretty cheap and your time has to be worth something. Crawling back under to fix a leak definatly is.

To say that working with PEX and a crimper is easy is an understatement. Although in a tight crawlspace you may not be able to get a good grip angle so avoid joints in those spots.

Part of the percieved problem with PEX as with the old Quest is pretty much anyone who bought a crimptool became a plumber overnight. This lead to some shotty installations with unsupported piping comming out the walls at all kinds of wierd angles. It was like they were hooking up garden hose! This contributed to the bad rep that these systems still fight.

I have still not run as much PEX as I have copper and may never catch up with the past copper installations. (Especially on Commercial jobs. Still all copper here in VA.)

Flex and rigid copper installations are not common here but I think it could make sense for you if there is just not room for your body in spots. Solder is solder at the coupling.

Best of luck.

If you are worried about waiting for and wasting hot water, I would install a recirc pump. This would eliminate the freezing worry also. You could also insulate the pipe. If you can solder and that is what you are familiar with, go ahead and solder. If you are only running 15' of pipe, I would use pipe and not flexible tubing. This way you can brace everything with full nail soiux clips. Make all your solder joints in the open between the joists, not right against them. Mechanically clean both pipe and fitting, with sandcloth and fitting brushes, stir your flux and use a thin film. In some cases, you might want to fab up sets on the ground and then bring them in the crawl to lessen the number of akward joints you have to make. I would run 10' of 3/4" for the hot and then go 1/2" but that's just me.

Thanks much for the replies Scott and jjbex.... I very much appreciate the help !

Loop all the soft copper lines up into the walls and make your connections and manifolds there. 1/2" copper for a short run will be adequate for the hot water.

HJ,

Thanks for the reply. I'm not quite sure I follow your suggestion - could you tell me if I understand you correctly?

I need to supply three fixtures (toilet, lav, shower) all on the same 8' wall (small bathroom).

For the cold supply, are you suggesting that I run 3/4" soft copper up into the wall by the toilet, branch off back down into the crawlspace and up again for the lav and then branch off down into the crawl space and back up again for the shower? Or are you suggesting that these horizontal runs between fixtures be made within the walls and above the floor (in which case I would be drilling through the studs).

Make all the connections above the floor. If the fixtures are all on the same wall or on contiguous walls, then run the copper tubing in the wall. If they are separated or doors are intruding between them then run the soft copper back under the floor and come up at that location. Think like you are doing a concrete slab and do not make any connections under the floor. Then you do not have to worry about making solder joints where you could burn the house down, (especially if you are under it at the time).

Gotcha.... thanks again.

One (hopefully) final question.... are there any issues concerning condensation when you run copper horizontally through the wall? I am imagining water condensing on the cold pipe and dripping onto the studs.

Should there be any insulation or barrier when the copper passes through a stud?

It depends if a sleeve is needed. Some towns made us use fire caulk when we penetrated floors and studs, etc. I have seen people drill an oversize hole for the pipe to pass thru, then squirt expanding foam and center the pipe in the hole. So the foam acts like a plug and sleeve at the same time. If you are worried about condensation, you can insulate the pipe in the stud walls, also.

IF the pipes are in an outside wall there will be insulation around them. If an inside wall there will not be any moisture to condense.

Thanks again jjbex and hj !