A contractor has installed my 3/4 inlet, 1/2 outlet manifold using 3/4 tubing on the outlets. He used a few inches of 1/2 pex to connect the outlet tubes to the manifold.

This seems odd, but I’m not sure what the impact will be. Will this be noticeable?


  • 2
    Hello, and welcome to Home Improvement. Would you edit in a picture or two of the adaptation? And, you should probably take our tour so you'll know how best to participate here. – Daniel Griscom Oct 24 '19 at 23:02
  • Done. Thanks, seems my title could be improved. – originalbryan Oct 26 '19 at 2:44

If 1/2 PEX would have been large enough to do the runs but the contractor used 3/4 instead, then:

  • he (you?) paid the higher per-foot cost on the larger tube and paid for each adapter
  • the tube holds more water, so if this is a hot water run, it'll take comparatively longer for the hot water to arrive at the fixture.

If the runs really do merit the use of 3/4 PEX, then:

  • there's a bit of a flow restriction at that undersize manifold which results in more pressure loss than you might otherwise have had, but if this is in an average home, it probably won't be noticeable.

In the world of plumbing there are endless permutations of fittings and size combinations that could be made, and a great many that actually are available. Sometimes exactly the right purpose-made fitting isn't used (in other words, an "odd" combination of adapters/sizes are substituted as on your job) because the plumber decides to get it done with whatever he actually has on the truck today.

  • Thanks you for the reply! The more I thought about it since posting, the more concerned I was getting. Sounds like it’s not a huge deal. 90% of my bathroom/kitchen faucets are very close to the manifold. There is one long run to a high use area I might need to downsize if hot water is taking too long. – originalbryan Oct 24 '19 at 23:14

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