I have 2 bathrooms that share a wall on our 2nd floor. Both have independent supply lines for hot and cold for each bathroom. One of the hot water supply lines was inoperable so I capped it and added a T from the other hot water supply as shown here:

Alternate supply line

Of course the hot water lines are on the outside of both sets of pipes and the sink drain in the middle. So, to be able to run the pex around the cold water supply and get it past the drain, it's resting against the cold water supply. As shown here:

rubbing pipes

Is this against code? Can these pipes be touching and resting against each other?

  • 2
    Not a plumber, not in the US... I have seen plumbers use a blob of silicone (I think) to glue the pipes together, preventing any chafing or banging caused by vibrations or water hammer. Commented Jul 10, 2019 at 4:55
  • Why is the old hot water line inoperable? Is the cap at the end of a long "dead leg" still connected to the hot water supply? Water in a dead leg is unswept by water flow and this can provide harborage for bacteria to grow. Commented Jul 10, 2019 at 11:53
  • @JimStewart It is still connected, and inaccessible at the source. If I can clear the blockage I take it you'd recommend undoing this?
    – Erich
    Commented Jul 10, 2019 at 13:43
  • Not necessarily. But do you know where the blockage is and what is the nature of the blockage? How far from the main hot water line is the blockage? Or to put it another way how long is the dead leg? Commented Jul 10, 2019 at 14:20
  • You are not supposed to use "push to connect" fittings inside a wall. I recently opened up a wall to do some connections for a bathroom above the wall and found a hidden in the wall push to connect fitting that was slowly leaking. The wall framing was rotted at the bottom and I had to rebuild the wall. The home owner was unaware of the leaking fitting inside the wall. It ended up costing the home owner several thousand dollars on top of the initial bathroom remodel.
    – Alaska Man
    Commented Jul 10, 2019 at 17:26

3 Answers 3


The only real issue is rattling noise due to vibration, or creaking due to thermal expansion. In this case, since one pipe is plastic, it's probably not a concern. I'd try to lighten the tension between them by flexing the plastic a bit, or place a rag between to act as a silencer. Be sure that by doing so you don't create a tight spot against the lumber, which can also cause noise.


I don't know about your local regulations, which you should look up yourself. But, to avoid heat loss, I would wrap the new pipe with an insulating sleeve, or, install one that was pre-insulated.

pipe insulation

  • 1
    There is no significant heat loss for that short run of PEX in air compared to all that copper. There is no room for this insulation. Commented Jul 10, 2019 at 11:49
  • Actually, now you mention it, I'd suggest insulating all the supply copper pipes as well if at all possible. Seeing the photo I would have thought that there is room enough to do so, as the insulation material can be compressed at the places where the pipes touch. I might be mistaken on the available space, but I'd try it out once with some isulating material.
    – user89225
    Commented Jul 11, 2019 at 6:15
  • In the majority of other places in this house the hot water pipes are open to the air. It will not make any difference to insulate the lines in a small place where there is access. Commented Jul 11, 2019 at 10:22

Get a u-shaped insulated bracket and screw it over the Pex to hold the pipe closer to the wall. If there isn't enough room to do that, I'd run the pipe a different way.

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