Plumbing Tips for Water Heaters

April 17, 2022
Choose the best piping with the correct diameter for your water heater.

Water heaters are such an important feature in your home that you really do need to make sure that all the features are just right, including the piping you use. Here, you’ll find some tips about the water piping to use with your water heater.

What type of pipe is used for water heaters?

Make sure the pipes for your water heater will be able to accommodate both hot and cold water. The pipes must also be able to tolerate the water pressure and flow. If the pipes run outside the building, they must also withstand the ultraviolet effects of sunlight. It is also essential that the pipes you use will not corrode.

Copper pipes

Historically, copper piping was most commonly used for almost all plumbing features. It is readily available and is durable and quite light. It is also relatively environmentally friendly and can handle the pressure of cold and hot water.

Copper piping is not particularly flexible but has the added advantage of being quite light to work with and fire-resistant.

One of the drawbacks of copper piping for your water heater is that it’s quite expensive. A metal flavor can also enter the water. However, because you won’t drink water from your heater, this is not likely to be a disadvantage.

PEX piping

A more modern alternative to copper piping to use for your water heater is Cross-linked Polyurethane (PEX) piping, which is fast becoming a standard for plumbing.

PEX does not corrode, so can be used quite safely for both cold and hot water. Because it can expand and contract, the pressure or the different temperatures of heat do not cause it to crack. This type of piping is also affordable and helps to preserve energy.

A great attraction of PEX piping is that it is color-coded: red piping for hot water, blue for cold water, and white for both.

One of the drawbacks of PEX piping is that you need some specialized tools to work with them. However, the piping is quite easy to work with.

What size is the inlet and outlet on hot water heaters?

The most common size of piping and inlets and outlets for a home is ¾ inch (1.9 cm). or 1.2 inches (1.25 cm). Most water heaters need a ¾ inch diameter of inlet and outlet, but a tankless heater can need a slightly bigger diameter of ¾ inch to 1 inch (1.9 to 2.5 cm).

A water heater is classified as having 1.5 fixture units, which is a design feature linked to the draining of water. If you take into account all the plumbing features in your house, then you will need a ¾ inch (1.9 cm) diameter, as it can accommodate up to 10 fixture units.

What to avoid

If the pipes for your water heater run outside your house, avoid using PEX piping, as it can be sensitive to ultraviolet light. It may also be an idea to avoid using copper piping, as it is rather old-fashioned and more expensive than plastic-based piping.


Choosing what piping to use with your water heater depends quite a lot on where you will place the piping and whether you are going to install it yourself. Craigs Services specialize in heat pumps and can help you with every aspect of the installation of your water heater.

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