PEX sizing?

[STLRooster]

Hi all,

I am going to start the process of plumbing soon, and I am curious about the diameter of PEX plumbing lines. There is a wide variety, so what size is best? Seems there must be a perfect equilibrium on sizing. What does it depend on? Distance run? Amount of tubing?

Thanks for the advice.

[HiHoAgRV]

All of my local Big Box Stores carry mainly 1/2". I mail ordered all my supplies and went with all 1/2" and have been happy.

[wxbuoy]

Concur with HiHoAgRV. 1/2 is plenty for an rv since you wont have someone in the shower while someone is washing dishes and another person flushes the toilet.

You also have the advantage that it and connections are available everywhere if you ever need them. Not to mention that most of us travel with spare shark bite, no tools needed, connectors.

[crabbey1]

I used half inch all around. Recently though, I read a thread where someone recommended using 3/8" and it made sense to me. My shower is quite a ways from the hot water heater, so there is a a lot of water being wasted into the grey tank waiting for the hot water to make it over there. If I had used 3/8" instead, much less water would be wasted and less space taken up in the grey tank. Plus all the fittings are cheaper at smaller sizes. I see plenty of benefits...

[Kevin245]

1/2" is pretty standard inside. I ran 3/4" from the spigot to my city water hookup, but everything beyond that point is factory pex.

[DKB_SATX]

Originally Posted by crabbey1

I used half inch all around. Recently though, I read a thread where someone recommended using 3/8" and it made sense to me. My shower is quite a ways from the hot water heater, so there is a a lot of water being wasted into the grey tank waiting for the hot water to make it over there. If I had used 3/8" instead, much less water would be wasted and less space taken up in the grey tank. Plus all the fittings are cheaper at smaller sizes. I see plenty of benefits...

I've actually been thinking about how much water is in the lines lately, because the plumbing lines on my 28' rear-bedroom run from ahead of the wheel well on the street side to the back, around the back curve and back up to the middle of the wheel well on the curbside where the shower is. I'm considering crossing the trailer under the floor to cut out about 15'-18' of pipe.

When I did the calculations, though, the return isn't huge. 15' of 1/2" PEX holds about 0.61 gallons. 15' of 3/8 holds about 0.34 gallons, so the difference between 1/2 and 3/8 is just over a quart. I may still shorten the pipe runs IF it's convenient to do so... there must already be a furnace duct running across there on mine, so I'm still thinking about it. I'm going to stick with 1/2" though.

[crabbey1]

Sure on one shower it doesn't seem major. While boon docking though, 4 showers would be a gallon of water saved and a gallon of space in the grey tank. Seems good to me...