I would like to slowly re-plumb my house with pex pipe. I would like to use the smallest dia. Pipe to reduce volume of hot water wasted. How do a figure if it can be done with 3/8. Or is this just out of the question. The longest run to a bath room is 50ft; The short to the kitchen 40ft. Water pressure is good.

Hi Dave...

Toilets and sinks already reduce to 3/8" at the shutoffs. Showers are at a minimum 1/2" tubing.

However, you probably shouldn't reduce the tubing size to the fixtures... instead, put flow control/volume control at each fixture..?

Think of it this way...

Someone is using the shower and then someone flushes the toilet... any idea what will happen to the shower water? It won't be nice for person taking the shower... ;) Not only will pressure be reduced but water VOLUME will also be reduced to a trickle with 3/8" tubing

Anyway, I would run at a minimum 1/2" pex to all fixtures... and I would run a 3/4" main line to connect all 1/2" pex lines. I'm not even sure they make a 3/8" pex... if they did then the Inside Diameter of the fittings would be more like a 1/4"... not close to reasonable.

They make low flow shower heads... they even have shower timers (parents with teenagers seem to like this). They also make low flow faucet aerators. I would not mess with the toilet supply.

Glad to discuss more if you want...

MARK

Is not always about water pressure. For example if water pressure is a little low the volume of a pipe can make up for that. If the pipe was 1/8 inch and twice the pressure it would not keep up with a 3/4 pipe in volume under less pressure. In a standard plumbing job 1/2 lines are used for horizontal runs but to get to another story 3/4 lines are used to compensate in volume what was lost if gravity working against the pressure. The old days the used 3/8 pipe for hot water and it was the old days where their was usually one bath and sink. Today homes demand much more volume even though the pressure is the same. Right out of the gate I recommend 3/4 main feeds off service and in basement to supply the other two floors with good volume
Stick with the standard 1/2" water horizontal line and 3/4 risers feeds to the next floor
Insulate the pipe and you will gain more no matter 3/8 or 1/2 etc If you can keep the hot water hot to the fixture then you turn that knob a tad less on the hot side and save hot water

Signed 21 Boat

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