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I'm planning water inlet for house:

  • For 2-4 people
  • 300m2 garden watering system ocasionaly (there is seperate garden water inlet as well)
  • Water comes in via 32mm PE pipe (internal diameter 26 mm ~ 1") from shared deep well pump.

Main question now - what should all inlet system connection sizes be? Valves, regulators, expansion reservoir (1" connector), check valves, meter, particle filter, water softener filter (1" connectors), etc., not including branch-off to kitchen/bathroom that would be different sized. My initial thought was 1", but some of those are more widely listed as 3/4" in local shops (regulators, meters).

Will 3/4" give any noticeable bottlenecks here? Should I go all 1" here?

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  • Is this residential? Is this new build or rework on existing build? What material for the inlet and all connected plumbing? Where are you located? What do your neighbors use? What is the size of the building (sqft)? Is it single story? Have you checked your local building codes?
    – Tyler M
    Jun 29, 2020 at 12:21

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I've worked on a house where the 1" input was immediately reduced to half inch. Stupid, and part of my work was replacing that.

Keep everything 1" up to the hot/cold split (i.e., the point where the cold feed for the water heater leaves the rest of the cold water - so pressure tank, water softener filters - why would you have a meter? Is that due to the sharing?), at which point 3/4" for each side and 1/2" to individual fixtures. I prefer to use 3/4" for hose bibbs (which only gets reduced to 1/2" at the hose bibb connection, since if a 3/4" connector hose bibb exists, it's a rare and likely expensive beast.)

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  • Meter is for sharing, yes
    – lietus
    Jun 30, 2020 at 13:07
  • I see that all components for 1" is around 30-40% more expensive compared to 3/4" (meters, valves, etc.). Does 1-2 meters of 3/4 piping/components reduce flow/pressure in meaningful way? Pipe length vs losses are easy to calculate, not sure about various components
    – lietus
    Jul 1, 2020 at 13:48
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    The hole in the pipe is 43% smaller, 3/4 .vs. 1 inch. When or how much that will affect your use is going to depend on your use/flow rate, but it's certainly a restriction that will reduce pressure as flow rates increase. i.e. at no flow, any size hole makes no difference in pressure. As flow increases, so does the effect (dynamic head loss) of the size of the pipe. You can evaluate the effect by using "total dynamic head" calculators, but the net effect is that at higher flow rates pressure drops more, and as a result the annoying interactions of multiple uses of water increase.
    – Ecnerwal
    Jul 1, 2020 at 13:58
  • I agree with Ecnerwal keep the pipe full size or when a hose bib is turned on outside you will have low pressure inside.
    – Ed Beal
    Jul 1, 2020 at 21:23

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