plumbing layout

[dug]

I'm trying to figure out how to best plumb my house. My main question is whether to run the lines under the floor or through the walls.

I like the idea of running them under the floor because it be easier to track down and fix leaks, as well as minimizing potential water damage. The down side is they would be more prone to freezing and part of the water lines would be in the wall anyway. For some reason it bothers me to run all the lines through the walls but maybe it is the better option.

Also- I am using pex tubing and wonder if it is worthwhile to use a manifold system. There will be five supply lines in the house with the longest run being about 15 ft. from the incoming line.

[MountainDon]

My opinion is to put the PEX in the walls or in a chase (box) on the inside of the insulated walls. Under the floor is great if there is a basement like in our old house back home.  Pipes generally do not leak, they might leak at connections id the connection is not done right or there is freezing. PEX itself expands if water is frozen inside the PEX.

I like manifolds because they permit shutting down one branch while leaving the others active. Nice for showers, tubs, laundry and exterior spigots that usually do not have under the sink shut offs. Manifolding the branches uses more tubing but that is not a great expense if the materials estimate is done properly and a large coil is bought. Some people use reb and blue, hot and cold, color coding. I did all the cold lines firest and marked them with blue tape.

In case there may be times when the home is left vacant and unheated it might be a good idea to plan sloping lines and low point drains. Or place a fitting to enable blowing the lines out with compressed air.

[jdhen]

I ran some underneath and some in the walls.  Of course, I was able to insulate the inside of the crawlspace with rigid insulation so there's no problem with freezing.  I would recommend the manifold.  There have already been several occasions where I've done some maintenance and been able easily turn off the water on the one outlet instead of the whole house.  It only adds about $150 to the total cost.

[considerations]

My PEX is under the floor, with stubs to each fixture.  Under the floor they are wrapped together in foam pipe insulation, then tucked into the insulation between the floor joists.  Our western Washington winters tend to be mild relative to many places in the states, but I think the hot and cold touching will help during those cold spells.