Properly size your plumbing (2023)

Water Line Size - The red arrows indicate a large diameter 1 inch supply line for all hot water in a home. Behind on the wall are smaller diameter 5/8 inch umbilicals to each light fixture. Copyright 2021 Tim Carter

"The size of the waterline determines the amount of water that will flow out of a pipe. Bigger is better when you need a lot of water in a short amount of time."

Revised February 2021

Size Waterline TIPS

Larger diameter water pipes create less friction
1 inch pipe less than 100 feet to a house is good
Size Waterline Videos BELOW
8 inch diameter water pipe supplies hundreds of homes
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My guess is that most people don't think twice about how much water will be flowing out of the faucets in their new home. You might not even think about how loud water is when it rushes through water pipes.

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As you move into a new home, you might expect a waterfall of water to cascade from every faucet and hose bib.

(Video) Plumbing Basics - Pipe Sizing Calculation - Bathroom Plumbing

Don't count on it. Your builder or plumber may have made some mistakes that can limit the amount of water flowing out of faucets. The same bugs can also cause significant hookah noise that drowns out conversations and other pleasant noises in your home.

Size waterline video

This short video is awesome. Pay attention to the first two numbers he quotes!!! HUGE difference in volume for just a tiny increase in pipe diameter!

If you live near a water tower, you want to be as far downhill from it as possible. Typically, these towers are placed at high points in the landscape. To have the best water pressure, you want to be in a valley with as much vertical clearance as possible between you and the bottom of the tank. The greater this distance, the greater the hydrostatic pressure.

High water pressure from above

For example, in Cincinnati, Ohio, if you have a home in the Mill Creek Valley under all the hills above you where the water tanks are, your water pressure can easily exceed 200 pounds per square inch (PSI). The land above the valley is 400 feet higher in elevation. The weight of the water in the pipes between the valley and the hills above pushes down and creates very high pressure.

When you try to push water through a pipe from a basement to a second floor, gravity does its best to exert an opposing force against the water pressure. Gravity becomes your friend and increases water pressure when you store your water on your roof, but how many people do you know who have 5,000 gallon storage tanks in their attics?

You will find this in large office towers, hotels, hospitals and other buildings where many people could use the plumbing system at the same time.

3/4 inch is fine | 1 inch is better

You need to have plenty of water capacity in your home, even if you don't need it all the time. For most homes in most cities, 3/4-inch pipe may be sufficient, but if you have the ability to specify the pipe size, substitute 1-inch pipe. I'm a master plumber and believe me you'll never regret it.

Plumbers and construction workers know that people rarely turn on more than three or four taps at a time. But it can happen.

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If you want plenty of water flowing from every faucet, you need to be sure that the water main entering the house and the main supply pipe in the house are at least three-quarters of an inch in diameter, or possibly an inch in diameter. This larger pipe can carry a significant amount of water.

Size waterline software

Watch this short video to see some computer software to help you SIZE your water lines. It comes from Australia, but the principles are the same all over the world.

opens in a new windowCLICK HERE to get FREE & FAST QUOTES from Plumbers in your cityto increase your water pressure.

Rural well water pipes

Make sure your well builder runs 1 1/4 inch plastic tubing from the well to inside your home. It's usually a short distance and you'll never regret the bigger pipe. Remember that it is easy to insert the right size pipe when the trench is open. If you try later, it's an enormous, expensive job.

If your house is far from the water main, up a hill and installing a water main is a monster job, you can't go wrong. It's worth a $500 fee, even $750 to pay a mechanical engineer to size the water line you need. It is very likely that if your home is 500 or 1,000 feet from the municipal water line, you will need a 2 or 2.5 inch diameter water line. DO NOT GUESS. You will regret it.

Install big pipes in ALL bathrooms!

All too often, an inexperienced plumber could start reducing the size of the plumbing in a home prematurely. When you see half-inch diameter water lines feeding two or more fittings, trouble may be lurking just around the corner. If your new home has three or more bathrooms, consider keeping the cold water line size at one inch until it has serviced the water heater, the first bathroom set, and possibly an outside hose bib or two.

The water main can then be reduced to three quarters of an inch in diameter to service the remaining bathrooms, laundry room, hose bibs, etc. Half-inch diameter tubing may branch off from the three-quarter inch diameter line to service individual fittings. Extend the three-quarter inch line until you get to the last two or three lights in the house.

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This is very important if you want great pressure and volume in all bathrooms.

Large diameter pipes are quieter

Pipe noise is also a function of pipe size. Larger diameter pipes produce less noise because the speed of the water moving through the pipe towards the fitting is slower. You can also minimize pipe noise by specifying a thicker pipe size.

If you're using copper piping in your new home, there's a good chance you'll be using M-type copper indoors. This is the thinnest tube allowed by most plumbing codes. Thin tubes transmit noise better than thicker tubes.

Also use thicker pipes

The next thicker tube type is L-copper. Consider a piece of L vs M copper and you won't see any difference. But take a 10-foot piece of each and you'll immediately see that the L-type copper weighs more. This extra copper absorbs sound.

The fantastic news is that the cost increase for L-type copper in a typical residential home is less than $275.00. (Prices as of 2017) This is a one-time fee that allows you to have quiet water supply lines for the life of the home. It's a very small price to pay for peace and quiet.

Drill large through holes

Finally, make sure the pipes are not pinched when passing through wall studs, wall panels, and floor joists. The holes need to be slightly oversized to allow the water lines to expand and contract freely.

Rubber pieces can also be placed between the tubes and each wooden frame to dampen vibrations. Attaching the rubber strips can be a chore, but any acoustics engineer will tell you that it helps stop noise transmission.