Shop Products
Houzz Logo Print
rmverb

PEX... Is a manifold necessary?

rmverb
9 years ago

Getting ready to build a house and currently talking to builders. One of the guys we like doesn't use a manifold as part of his standard plumbing. He says it's not necessary and homeowners really don't need one. Is this true? He said it will add about 1k to the plumbing cost. Should I insist on a manifold, or is it really no big deal?

Comments (8)

  • sid_79
    9 years ago

    I'm building a new house and what we ended up doing is a 1" PEX for the main cold line and 3/4" for hot. Every fixture tees off that with 1/2" PEX home run and dedicated shut off. The main lines are about 20' long and run in parallel a couple feet apart. My 3 bathrooms and laundry are all located directly above these on the first and second floor so most of the 1/2" runs are quite short. This has the benefit that each fixture has it's own shutoff and there are no tees in the walls. Cheaper than a manifold.

  • kirkhall
    9 years ago

    It is not required with PEX. It can be handy.

  • Bruce in Northern Virginia
    9 years ago

    If he does not use a manifold then you are just installing like a direct replacement for copper. That's not necessarily bad, but you lose some of the advantages of having a manifold where you can shut off each line individually and work on one fixture while leaving everything else on. The remote shutoff is really convenient when you need to replace an individual shutoff valve for a toilet or a sink.

    You could also ask him to install a hybrid system, where you run a main line, but then install a manifold at each group of fixtures. It requires less 1/2" piping, but still gives you the ability to shut off water for each fixture.

    Bruce

  • Vith
    9 years ago

    It is not required but it is nice to have. Think of it like an electric panel, but for your water lines. If you need to shut off a room its easy to do without interrupting the rest of the house. Also, it helps balance pressure so you dont get a burst of hot water in the shower when someone flushes a toilet.

    I put manifolds in my house when I redid it to PEX; one for hot, one for cold. The hot has 4 valves the cold has 6 valves (I have one extra on the cold for future expansion if needed). The branches I did are for kitchen, upstairs bath, downstairs bath, laundry room, and exterior faucets. Your plumber may be thinking he has to have a valve for each fixture which would be expensive, instead you can ask that he does a valve for each room. Thats what I did and its proven handy and wasnt that much more maybe 150-200 more for the manifolds and valves.

  • greasetrap
    9 years ago

    Not to change the subject, but the inside diameter of PEX seems to be much smaller than the same size copper pipe. So it seems to me that it would carry less water than the same size in copper. Is this correct?

  • AliceHasLeftTheBuilding
    9 years ago

    No. It means it will hold less water when the water is not moving. Pex has a lower friction coefficient (it's slipperier) so you can move move the same amount of water through a slightly smaller diameter pipe. The water moves a little faster. I can explain the whole fluid flow through a pipe, edge effects, turbulence, friction model if you would like.

  • greasetrap
    9 years ago

    Thanks for explaining that. No need to get into fluid dynamics - the simple explanation is fine for me.