1/2 vs 3/4 water pipe

[petertay15]

Our house is plumbed with 3/4 copper. It takes soo long for hot water to reach the upstairs bathroom. If I replace as much 3/4 as I can reach in the basement with smaller pipe, will that cause grief due to smaller volume pushing larger volume? Thanks. --Peter

[Splinter Puller]

A compromise would be to home run 1/2" pex lines from each location back to a manifold at the heater.

[Howardly]

1/2" pex measures 3/8" ID. The hot water would get to that bathroom sooner but at a loss of volume.

[GHR]

No, that is not a problem.

The code relates the required pipe size to the number of "fixture units" it supplies. It is best to respect the code.

[petertay15]

Thanks for the suggestion. About 15 feet of 3/4 hot water runs across the basement ceiling, then goes up in the wall. So it will be easy to run a smaller pex across the ceiling, but I'm wondering if pushing the heavier column of water up the wall will slow things down. Our pressure (private well) is about 30 psi.

[jteneyck]

The water won't lift the whole column. The 1/2" line will flow into the 3/4" one, mix with it, and flow out the top, and the flow will be higher than having 1/2" the whole way. It likely will take longer for the temp. to reach it's max., however, vs. having 1/2" the whole way. PEX would be my choice if I were going to the trouble of replacing lines. No soldering, likely higher flow, easy to snake around obstacles, and hot water faster at the other end.

John

[petertay15]

Thanks, John. I always appreciate your replies to people. --Peter

[fixtureman]

If you put in a circulating system

[blackhat]

A recirc is the correct solution to your problem. Preferably one that is time and temp based.

[jteneyck]

blackhat said:

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A recirc is the correct solution to your problem. Preferably one that is time and temp based.

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Does this really make sense? All you save is a little water and even less fuel/power. Doesn't it still take about the same time for hot water to get to the outlet. And you need to buy and install a pump and return line to do it. What am I missing that makes this a good option?

John