Pex repipe of galvonized iron

[diyguy]

Hi -
I am planning to repipe a lot (if not all) of my 3bedrm/2bath house with Pex. The 45 year old galvanized pipe has some very slight leaks in a couple of joints in the crawl space, so I think it is time. There is also a lot of rust that comes out after the pipes sit idle for awhile.

I was planning to stick with main and branch rather than manifold system. I plan to use 3/4" Pex and branch off with 1/2" pex to most fixtures, much like it is currently with 3/4" iron pipe with 1/2" risers. Basically, I am replacing iron with pex -- no redesign or changes to speak of. One thing that may happen, however, is that I would run slightly longer 1/2" runs to some fixtures. This is because I am thinking of running the 3/4" Pex from the supply and WH more centrally down the middle of the house, then running longer 1/2" runs over to some of the fittings. Any comments on this idea? Is 3/4" Pex sufficient as a replacement to 3/4" iron?

ISSUE #1: How do I handle running the pex up from the crawl space to the bathroom fixtures. Both bathrooms have original tile walls that are in great shape and I do not want to tear them up.

Can 1/2" pex run up from the crawl space, then bend out 90 degrees through the existing openings? Currently, 1/2" pipe extends up through the floors to a 90 degree elbow, then a 1/2" nipple out through the wall to the shut off valves. this is for both lavatories and both toilets. If I bend 1/2" pex out through the wall, can the pex support a shut-off valve (using pex to 1/2"MIP adaptor) or do I need any kind of reinforcement/support for the pex?

Any tips or tricks on working pex through the existing path of iron pipe -- how to make a bend coming up from crawl space to go out through an approximately 1" hole in the wall. Is it easier to run the pex into the hole in the wall and down to the crawl space, or up from the crawl space and out through the hole in the wall? Any help is appreciated -- I would hate to start this only to find that it is not a workable solution.

I will consider using copper to replace some of the iron pipe near the fixtures (that is, if it is not possible to get the pex to run through). In that case, again without tearing up the tile, how can I replace iron with copper through the existing 1" holes in the wall and in the floors?

ISSUE #2: The shower fixture is also behind tile and quite inaccessible. My thought is to leave the iron pipe in place for the shower fixture from the crawl space up to that fixture. I would replace the iron pipe in the crawl space to the point where the iron takes a 90 degree elbow up to the fixtures. The problem is how to support the iron pipe and shower fixtures since it will no longer be attached/supported by the rigid iron pipe currently running in the crawl space. Any suggestions? I have a similar situation with the two hose bibs -- no support for the bibs, which are currently only supported by the iron pipe and do not attach to the brick on the outside of the house.

I look forward to any comments, suggestions, and advice.

[jeffreyhel]

PEX pipe is a great solution for many installations. How many stories is this house in question? I am assuming that it is a single level house. You cannot make sharp turns using PEX tubing but can use PEX elbows and other fittings. I usually drill new holes from the bathroom down and run the new pipes. The old ones I remove and caulk or grout the holes. I use Wirsbo Aqua PEX water piping. Your 3/4 water lines for main hot and cold will do the job but you must continue the 3/4 until the last two fixtures of each bathroom. Example you would run your cold 3/4 and branch off 3/4 to one bathroom where you would continue 3/4 until you got to your last two branches for that bathroom. Individual fixture water supplies connect into water mains and branches in 1/2 generally and vary depending on demand. Such as a juccuzzi where it should be 3/4 all the way to the tub.

If the shower valve feels like it's falling when you disconnect it from the old water main, then you need to figure out a way of securring the faucet.The shower valve should be securred from the original installation and I wouldn't worry too much about it falling. Take real care when removing old pipe from pipe that you want to remain. All to many times you can cause more leaking behind the walls.