Currently plumbing a 20" rain shower (droplets + water fall). Using it with a water pump/booster.

The valve that comes with it has two 1/2" inlet which consists of cold + hot water so it's basically a 3/4" feed.

It however only has one 1/2" outlet.

So my question is does it help if i connect 3/4" pipe to that outlet after using reducer coupling? In this sequence:

Outlet > 1ft of 1/2" pipe > 10ft of 3/4" pipe > Rain Shower

I know bigger pipe helps with friction but it's of no concern here as the distance is short.

My concern is more on whether this arrangement will produce a 3/4" water flow instead of a 1/2" water flow and whether i should just go fully 1/2" in order to avoid wasting hot water that are sitting in the pipe since the flow of the said arrangement is just going to be the same as a 1/2" flow.


  • The reason it uses 1/2" pipe is because that's the smallest size commonly in use; not because it needs the flow. Nov 15, 2019 at 17:56

1 Answer 1


The hot/cold mixer valve and/or the 1/2" valve outlet make installation of 3/4" pipe, downstream on the run to the shower head, unnecessary; you will have no appreciable benefit from this. Also, I imagine that your "rain shower" unit has a 1/2" inlet (although you don't mention this).

Your concern about "wasting hot water" doesn't make sense to me; your proposed pipe size increase is after the hot and cold mixer...

  • 1
    OP is referring to the heated water left abandoned in the pipe between valve and head. Heating that isn't free. Nov 15, 2019 at 17:57
  • 1
    the extra 29 cubic inches...
    – JACK
    Nov 15, 2019 at 18:12
  • 10 feet of 3/4" pipe holds .23 gallons (about 3.6 cups) of water. Consider roughly half of that would be cold water from the mix. You can decide if that's "wasting", but personally I wouldn't lose too much sleep over it. You could make a bigger impact by taking shorter showers.
    – Jamie M
    Nov 15, 2019 at 18:17
  • 1
    @JamieM He's only wasting the difference between the 3/4 and 1/2 inch pipes..
    – JACK
    Nov 15, 2019 at 18:28
  • 1
    Good point, that drops it to 2 cups/0.13 gal
    – Jamie M
    Nov 15, 2019 at 18:34

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