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We're plumbing our new basement bathroom. The nearest fixture from the main hot/cold water line will be the vanity sink.

Can I run from the main line to the vanity sink (one faucet), and then branch to toilet and shower (no tub)? All with 1/2" PEX.

Distances: Main line to sink = 15' Sink to toilet = 5' Sink to shower = 6'

Thank you.

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  • Yes, that's not a problem in regards to water pressure nor volume. You will be able to comfortably wash your hands right after flushing the toilet but if you're showering then I advise not using the other 2 fixtures at that same time. If you are planning to run multiple fixtures at once then just remember that one 3/4" pipe has the same volume as 2 1/2" pipes. Whether or not you have enough pressure in your main line to not notice a difference when two fixtures are being used is a different topic :-) – MonkeyZeus Nov 23 '20 at 19:26
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I did something similar in my son's tiny house.

But I did an individual run to each item (kitchen sink, toilet, shower and bathroom sink) to limit the joints used to the ends only.

Much easier not to worry about leaks hidden in walls (just have to remember if fixing things with screws).

The professional plumber looked and said that was what he would do as the pipe is cheap and the consequences of one leaking tee joint are expensive.

A roll of the pipe (25m) is about 75 feet so you will still have some left.

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  • I see the advantage of not having the Tees buried in the wall, but aren't there just as many joints to potentially leak at the "home" location as there would be at the Tees? I'd have the Tees accessible under the vanity, having 2 there, one to go to the toilet, the other to the shower. – FreeMan Nov 23 '20 at 15:54
  • @FreeMan so two tees - is 6 joints plus the one at the beginning and one at the end is a total of 8. OP needs 3 runs each with a beginning and end so a total of 6 joints. And then factor in the possible pressure losses or noise from the tees... – Solar Mike Nov 23 '20 at 15:57
  • Fair enough.... – FreeMan Nov 23 '20 at 15:58
  • Thank you. This makes sense. Although our wall behind the fixtures remains open (partially finished basement), I agree with less joints and potential pressure loss. I'm going to run individual lines to the sink and shower. – William Lee Nov 23 '20 at 16:05
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You can but you might not want to.

PEX pipe being dirt cheap, it's common to "home run" back to the source, minimizing the effect of one use point drastically affecting the water pressure on another use point.

On the other hand, if you make the assumption that this bathroom will only be used by one person at a time, you can choose to discount the potential discomfort of having someone run the sink or flush the toilet during a shower.

Your call, really.

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