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What Size PEX Should I Use in My House? (Read This First!)

PEX is quite popular for water lines due to their availability. Apart from that, they cost less and are durable.

You can have an easy installation process of the waterline. Moreover, it leads water flow from the mainline and keeps it consistent and does not decrease the flow.

Following the below tips and information regarding PEX and the size of the pex which is preferable for using at home would give you an idea of the installation of the waterline.

What size PEX should I use in my house?

Pex is usually used in the size of ½ inch, ¾ inch, or 1 inch. The size depends on water lines, the pressure of water, and also the demand for water. Improper sizing of the pex pipe can cause a decrease in water flow with time. Moreover, low pressure inside the pex pipe can lead to no water flow.

Pex provides multiple facilities than a copper water line. It is cheap and easy to install. Though it can not stand UV rays, it does not form any chemical reaction in the water while flowing through it.

Still, many may suggest not to use pex as it can burst depending on the pressure and temperature.

For plumbing:

Pex is mostly used in water lines as it serves a variety of benefits.

The size of the pex pipe for the water line depends on many factors. The pipe size for the water line is mainly chosen depending on the water demand.

A small house would require less water supply than a bigger house depending on the number of showers, bathrooms, and kitchens.

According to the numbers of bathrooms and sinks, you would need to know the fixture number. The unit would also vary.

Moreover, a pipe needs to hold water pressure and should supply the demand water without dropping the pressure.

After considering all these, you can finally choose the pex diameter. Often people use a ¾ diameter pex for the waterline if the house is small.

It is a problem that ¾ can not handle too many fixtures. Meanwhile, ½ inch is used for manifold water lines. It can handle almost 14 fixtures.

If you have a big house, you might need a 1-inch pex size. It can hold almost 30 fixtures and flow water without dropping pressure.

Well, manifold size should be considered here too. The pex pipe should be fitted to the manifold. Otherwise, you can use the pipe.

Apart from that, the length of the pipe can also decrease water pressure which can result in decreasing water flow.

That’s why the diameter of the pipe should always be bigger. So that, it can provide greater pressure from the first.

After considering all these you can finally choose the size of the pex. Nevertheless, fixing water lines is tough, so better to go for professional help.

Can you use pex under a house?

You can definitely use pex under a house with proper insulation. Pex is highly restricted by many countries. Pex can not be installed at a place where it would get exposed to UV light. Moreover, high water pressure can cause the pex line to burst.

Using pex under a house is not suggested either. If the ground has a freezing temperature, there is a chance that the pex would burst.

You can also use pex underground. It would provide proper insulation around the pipe. You can bury the pex while covering it with sand.

Some may not recommend using pex under a house as it can be placed as a normal water line. You should avoid exposure to UV on it.

Yet, pex pipe can expand or contract with temperature. If the pipe is exposed to frost, it can even burst as the temperature is going to decrease.

Should I use PEX A or PEX B in my house?

Pex A is often used in the houses for water lines rather than pex B. Pex A and pex B are totally of the same size yet different. The pex A is considerably better than pex B. Pex A can expand which makes it easier to fit into lines.

Meanwhile, pex B loses some diameter while fitting. As a result, it can not flow the same amount of water as pex A.

It would consistently reduce water flow. Apart from that, pex A can handle weather changes. On the other hand, pex B can not stand weather changes.

Another difference is pex A is more flexible than pex B. Due to its flexibility, it can be bent and given shape to fit.

You can also fix pex A underground with proper insulation for water lines. Considering all these differences, pex A is more suitable for water lines rather than pex B.

What size PEX is used for main water line?

A ¾ or 1-inch pex is often used for the main water line. The water line supplies the water to the whole house. A simple mistake in choosing the pipe size can cause less water supply and sometimes no water supply.

Keeping the pressure through the pipe constant is a tough task if the pipe does not have a proper size.

A ¾ inch pex is usually used for water lines at small homes. It is the inner diameter of the pipe. It is not capable of supplying water to many fixtures. That’s why a 1-inch water line is also used for bigger houses.

The manifold size influences the pex diameter. As it has to fit into the manifold. You can also go with ½ inch pex size for branches. For a mainline of ¾ or 1 inch, you can use ½ inch pex for branches.

How to size PEX pipe for home plumbing?

Pex size for home plumbing depends on many factors. You need to go through every single one to know what size pex pipe is required for your home. Certain steps you can follow while choosing the size of the pex pipe are listed below.

Count fixtures:

The fixture unit differs depending on the pipes you may require. Well, bathroom sinks, and kitchen sinks all have a different fixture unit. Count all the fixtures at your home. And also their unit.

The length of the water supply:

The further away the water supply tank is the more pressure is required through the pipe to flow the water from the supply point to the designated area. With increased length, there is also a decrease in water flow.

You need to make sure enough pressure is provided through the pipe to flow the water. Apart from that, long length can cause water supply capacity to lose and it would decrease with time.


The pressure is required to let the water flow through the pipe. The diameter of the pipe influences the pressure of water. Moreover, pex can cause pressure drop.

Choose the size:

Moreover, a ½ inch pex is the highest size you should consider. Well, a ¾ inch pex is also suitable for smaller houses depending on the manifold size. It can supply water to almost 3 to 4 fixtures.

While a 1-inch water line can supply water to 30 fixtures approximately. On the other hand, ¾ can hold almost 14 fixtures. Choose according to your demand.

Where is pex used in the house?

Pex is usually used in the house serving various purposes. It can actually provide benefits in many ways. You can save your money as it is cheaper to install. You can use pex in the house for multiple purposes and those are given below.

As water supply line:

The most popular use of pex is in the waterline. Pex works smoothly to supply water while maintaining the flow of the water.

It does not deteriorate easily. You can also use it for longer times due to its durability. You can also use it for hot water lines and in heat transfer systems.


Pex is used under the house or under the ground. Still, proper insulation is required. Moreover, it cannot withstand high heat.

Rather place it far from direct UV rays. Placing it underground would keep it far from sunlight. Yet, freezing temperatures might cause harm if proper insulation is not done.

Final Thoughts

Overall, pex pipe size depends on the demand for water supply, pressure, and also on fixtures. People usually choose a ¾ or 1-inch water line of pex for houses. While ½ inch pex pipe can be used for branches. The size is highly influenced by fixtures; better consider those before choosing the size.