Supply line length

[Bwn250]

This may be a dumb question. But when running new supply lines that is branching off to two to three different fixtures. Is it better, worse, or doesn’t matter to have longer or shorter lines between them?

 

[Tuttles Revenge]

Not a dumb question at all.

Length and size do matter. Sizing is important in order to deliver a consistent pressure and flow or gallons per minute to each fixture.

Too small of size with high pressure creates too high of velocity which will wear out the tubing and fittings. Too large of pipe size can create areas with too low of movement and lead to stagnant water.

Sizing of water lines is determined by figuring out your total load by number and type of fixture. Knowing which pressure range you have. And distance overall from your water main to the furthest fixture (also each branch to a group of fixtures like a single bathroom can be calculated the same way). You can also calculate friction loss by number of elbows and pipe size, but that's really for larger projects and engineer nerds.

This code reference could help in sizing for your jurisdiction.

Chapter 6 Water Supply and Distribution: Water Supply and Distribution, Virginia Plumbing Code 2018 | UpCodes

UpCodes offers a consolidated resource of construction and building code grouped by jurisdiction

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[Breplum]

For simple homes, in a bathroom we usually use 1/2" copper feeding two fixtures, then a 3/4 x 1/2 x 1/2 feeding the bathroom itself.

 

[Jeff H Young]

If its just a lav toilet and shower 1/2 inch hot I might run 1/2 inch cold but I think it should be 3/4. good pressure and close to main in all copper itll be fine but its likely technically undersized. 2 Lavs , a toilet and a Tub/shower 3/4 branches hot and cold.
master tub with high flow valves 3/4 inch hot and cold all the way to the valve or a foot or so away