Your residential plumbing system includes all the pipes that transport water in and out of your house and across the city. Before you install any pipes in your house, you want to ensure that you install the right size of pipes for the appropriate use. 

For a professional plumber, there’s usually a guideline or a standard water pipe chart to consult. Also, there are different factors to consider when choosing the size of pipe to use. These factors will enable you to choose the right size of pipes for your plumbing system. These factors will be explained further in this article. 

How Do You Size Residential Plumbing

What Size Pipe Do I Need?

If you’re making renovations and you want to replace a pipe in your home, you can know the right size to choose by simply choosing the same size of pipe and reinstalling it. However, if you’re building from scratch, you need to figure out the right size of pipe to use. You can check your local building code’s pipe sizing chart for the right sizes of pipe to use. Below is a chart that can give you an idea of the appropriate sizes of pipes you can use:

Fixture or AppliancesCold Water PipeHot Water Pipe
Toilet 3/8”
Bathroom Sink3/8”3/8”
Kitchen Sink½”½”
Dishwasher 3/8” to ½”3/8” to ½”
Washing Machine½”½”
Laundry Sink1/2”½”
Water Heater¾”

Residential Water Pipe Sizing

Choosing the right size of pipe for your plumbing system depends on the water pressure in your home. The plumber must ensure that the required pressure for the home is maintained throughout all the remote fixtures. Also, the plumber must ensure that the velocity of water flowing through the pipes is coordinated and maintained. The water velocity in all piping shouldn’t be more than 10 feet/sec because any velocity higher than that would increase the chance of corrosion. And pipe corrosion would lead to pipe failure or possibly hydraulic shock. 

So when deciding the size of pipes, these factors should be considered;

  • Hydraulically remote fixtures

The most remote fixtures are the fixtures farther from the main domestic water supply point. The most hydraulically remote fixture is the fixture that is not very far away but the fixture that will have the least pressure considering the water that’d be coming into the house. 

  • Available main pressure

The plumber will thoroughly examine the main water pressure available at the house. If the pressure available in the house isn’t sufficient, then there’d be a need for an extra pump. Also, if the pressure is too high, then there’ll be a need for a pressure-regulating valve. High water pressure in the pipes can lead to unnecessary water loss or unsafe operations. 

  • The pressure required at individual fixtures

The plumber should research the plumbing fixtures and determine the pressure that would go into the pipes leading to it. For instance, tank water closets only need 5 psig while flush valve water closet need 15 psig. Each plumbing fixture requires a different amount of water pressure. Even plumbing fixtures from different manufacturers cannot operate with the same amount of water pressure.

  • Static pressure losses

The static pressure losses refer to the height of the highest fixture relative to the main pressure which is found in the difference between the first elevation at the main pressure point and the last elevation at the hydraulically remote fixture.

  • Friction Loss

Friction losses can be caused by the force of water flowing through the pipe. They are determined by finding the flow rate, velocity, pipe size, and roughness for the entire time water runs through the pipe. Friction losses can also be caused by the use of unnecessary equipment like valves, backflow preventers, water meters, and pressure regulating valves. 

  • Water Demand

The water demand is the amount of water expected to come into the house which is based on the water supply fixtures and other continuously used fixtures. As the water demand increases, so does the friction loss which reduces the pressure at the hydraulically remote fixtures. The water demand should be considered together with the pressure at the hydraulically remote fixture.

  • Velocity

The projected velocity can be found depending on the water demand. The velocity in the piping should be reduced to avoid too much noise and increased pipe erosion.

How Do You Size Residential Plumbing 2


Choosing the right size of pipes to use for your plumbing system shouldn’t be challenging if you hire the best residential plumbing contractor. At Rite Plumbing, we have plumbers who specialize in residential plumbing installations and residential plumbing repair. 

We’re available round the clock to attend to your plumbing needs and take care of emergency plumbing issues. Our services are top notch and you can rely on us to provide the best plumbing services. Contact us today to know more about our services!