View Full Version : Pex replacing PB, how much slack?

11-08-2009, 07:34 AM
My bathroom's PB plumbing has a fairly straightforward topology. The hot and cold pipes are hanging from the concrete-block exterior wall (well, it's exterior, but it's in direct contact with the neighbor's identical wall... think "two exterior walls built side by side with a sheet of tyvek between them, as opposed to what you'd normally think of as a party wall between townhomes"). They terminate at the shower, then run straight across the wall ~10 feet before disappearing behind the drywall of the next room over.

The sink and toilet are both Teed off.

Here's the main thing worrying me: I've read that PEX needs room to move and expand, and that one of the biggest causes of long-term PEX failure is installing it as if it were copper... in neat, straight, tight straight lines.

I've read that the best way to accommodate that is with large-radius loops. Is it OK to put a single such loop at some convenient point along the ~10 feet or so between the shower and where it exits the room, or does it have to be at roughly the halfway point between where it taps into the remaining PB at the entry point to the room & where it ends at the shower, or (god forbid) do I have to put one loop between the shower and sink tee, another between the sink and toilet tees, and then try to squeeze a third loop between the toilet tee and pb connection ~2 feet away?

If I have to use multiple loops, does the tee for the sink or toilet have to be in any particular orientation? Or could I do something like loop the supply line behind the sink, then cut the tubing at the apex and put the sink's tee there?

On a completely random note, does anyone sell small manifolds with 3 hot and 4 cold outputs that are small enough to reach all the valves through an opening big enough for a 4x4 electrical box? What "nice" options ARE there for hiding a small manifold like that in a bathroom where anyplace you put the panel is going to be visible & you want it to be relatively fast & easy to open, but not completely ugly? How much (give or take) is a manifold like that likely to cost? Pipe-wise, the old supply was 1/2", but I'm contemplating replacing it (at least to the shower) with 3/4", just in case I discover someday that the remainder of the old line IS accessible & can easily be replaced.