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Mechanical Room layout- best location for water main?

AdamPNW | Posted in General Questions on

Hi all, I’m designing the layout of our 7.5’x6’ mechanical room and trying to figure out the best location for the water main. 

I’ll be spec’ing a 119 gallon storage tank for the Sanco2 combi space heating system. The cold water inlet for the stratified tank is about 8” off the ground. 

The water main will be travel underground and come up through the “slabless” slab. Where is the best place to have it come up into the mechanical room so that it is easy to access, work around, perhaps leaving space for a future filters, etc?

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  1. AdamPNW | | #1

    For example, is it best practice to specify an exact location for the water main on the plans or is it enough to just get close enough and call it good? I’m trying to make life easier for the plumber when they hook up to the water heater.

    1. Expert Member
      MALCOLM TAYLOR | | #2


      Based solely on the drawings, I would bring it in between the WH and storage.

      You have three main floor fixtures that need both hot and cold water supplies, and cold water to the exterior wall for hose-bibs. I would work out the runs for those, which may inform where the main best comes in. You may want to consider sleeving all the water pipes under the concrete-less slab, which makes any replacement a lot easier.

      1. AdamPNW | | #5

        Thanks Malcolm. I think I understand- if the manifold that serves those fixtures is mounted on the south wall of the mechanical room (instead of storage), it will be closer and therefore reduce time to tap. Which means the inlet could go on the opposite side of the tank to keep things spaced out.

  2. Expert Member
    BILL WICHERS | | #3

    I prefer to put the water line coming up on (not in) one of the walls, so that it can be clamped to the wall and branch out from there.

    Do be sure that you keep the water line clear of electrical panels. You are not supposed to have potentially leaky things directly over electrical panels without using a protective drip pan to protect the panels.


    1. AdamPNW | | #6

      Thank you Bill. That’s helpful. In order to reduce the number of bends in the Pex inlet line, I think I would have to angle it diagonally from the wall where it is clamped, to the cold water inlet on the tank (which is centered on the tank). I can rotate the tank so that the inlet is point diagonally back towards the main. Is that typical?

      1. Expert Member
        BILL WICHERS | | #8

        I would use some 90 degree fittings and stay flat to the wall, then come out straight from the wall and 90 into the side of the tank. That gives a cleaner look than cutting diagonally across open air. You're unlikely to really notice any difference in flow with a few extra 90s in the line if that's what you were concerned about.


        1. AdamPNW | | #9

          Perfect thanks.

  3. Expert Member
    Michael Maines | | #4

    On a current project, space in the mechanical room is very tight so I suggested putting the water heater on a pedestal above the water line entrance.

    If you don't show the entrance on the plans, somebody else will decide where it should go and they may not understand all of the constraints as well as you do.

    1. AdamPNW | | #7

      Good point thanks Michael

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