Can PEX Be Used for Drain Pipe? (Read This First!)

There are several important parts of our house that remain hidden from plain sight but are crucial for the proper functioning of our household. 

Utilities such as electricity, water and gas are drawn into our house through different pipe lines within our house which enables us to use them at ease. 

Drain pipe is also a similar component of our house, therefore we need to understand the ins and outs of it and what type of pipes to use.

Can pex be used for drain pipe?

PEX is one of the most popular plastic pipes that can be used for drain pipes besides being used for electric and water lines. Pex is commonly used in appliances such as boilers too due to its properties such as flexibility, ability to hold water pressure while being low cost and easy to set up.

There are several types of plastic pipes that have replaced the use of copper pipes due to their immense advantages over their metallic counterparts. Among the plastic pipes, PVC and PEX pipes are some of the popular variants of plastic pipes that are used in water or drain lines. 

While PVC has been the market favorite for quite a while, pex pipes have been gaining popularity and becoming the industry standard for water-supply or drainage lines due to their durability and heat resistance. 

Pex pipes also have several variants among themselves which are better suited to specific environments. Usually red and blue pex pipes are seen in many households where the red ones are better at handling hot water lines while the blue ones are good at handling cold water. 

Other useful properties of the pex include rust-proofness and durability. Although pex can be used in both water lines and drain lines, pvc is commonly used in water lines whereas pex are seen more commonly in use as drain lines.

The material out of which pex is made of allows it to be excessively versatile and gives it an edge over other plastic pipes, few of the advantages of using pex is that it does not require any elbow fittings and can directly make a 90 degree turn thanks to its flexibility. 

It is also less likely to crack and burst at freezing temperatures due to their expandability. And unlike their metallic counterparts, they are immune to rusting and corrosion due to humidity or salinity of the environment.

Can pex be used underground?

Due to the durability and expandability, pex has been a popular choice for use in underground piping. Burying pex underground reduces the risk of hard piping due to freezing temperatures as well as damage to the pipe due to the freezing water at low temperatures. 

However, due to its flexibility and expandability, they can be used underground during freezing temperatures with the help of some tweaks.

One way to properly use pex underground is to bury the piping below the frost line which you can find out from your local or municipal water company. Another thing you can do is surround the piping with sand to prevent stone or rocks from damaging the pipe’s exterior.

Besides that, you should pick the right type of pex for burying – there are three types of pex but only two types: Pex A and Pex B can be buried underground since they have great flexibility and can withstand the expansions due to freezing and thawing of water.

Is PEX good for underground plumbing?

Pex is an excessively good choice for underground plumbing due to its expandability and its flexibility. However, not all types of pex are good for underground plumbing – there are three types of pex: Pex A, Pex B and Pex C. 

Pex B is the best out of the three for underground plumbing due to its greater rigidity over others which makes them less likely to burst under pressure or freezing. They are also good at preventing leached chemicals from seeping into the piping. 

Second in rank is the Pex A which is more soft and flexible in comparison to Pex B – which makes it more vulnerable to ruptures due to pressure than Pex B, making it come second to Pex B. 

However, Pex A provides much better performance against expansions due to freezing of water but they have burst at lower pressures than B.

Pex C is the type of pex that is not suitable for underground plumbing due to its stiffness and thus making it more vulnerable to kinking, cracking or bursting due to the freezing water.

4 reasons why you can use pex for drain pipe

Pex pipes are suitable for use as drain pipes due their durable properties such as:

Flexibility and durability:

Pex pipes are made of flexible materials which are durable while being able to bend without any breakage, this property of pex allows it to be fitted in ways the plumber sees fit. 

It also has greater advantage over other plastic pipes during freezing temperatures as their expandability can withstand the fluctuations due to the freezing and thawing of water. 

Ease of setup and connection:

Unlike copper pipes of pvc, pex is easier to connect – copper pipes need to be connected by soldering while pvc needs glue while pex is easily connected using a crimping tool. 

Besides that, they are not rigid as copper pipes and are more flexible than pvc which allows them to make 90 degree turns without breaking – thus reducing the need of elbow fittings at each turn.

Resistant to chemical reactions:

One of the biggest problems faced by copper pipes is that they are vulnerable to chemical reactions such as rust and corrosion – which heavily reduces their durability and longevity. 

However, plastic pipes such as pex are less likely to corrode from humidity or salinity of the environment. 

Suitable for use with both hot and cold water:

Apart from being lead-free, pex has another great advantage over copper pipes – they can be used to handle both hot and cold water. 

Copper or pvc pipes are not well adapted to perform well in both temperatures but pex can handle both temperatures as long as you use the right color coded pex pipe.

Which pex pipe to use for drain pipe? 

Pex pipes are available in many variations and colors, however each type has their own specialty – therefore it is best to know which pipe you should use for your drainage system. 

Pex pipes are primarily classified into three types: Pex A, Pex B and Pex C – however, all three of them can be used in drain lines but you need different color coded pex pipes for handling water of different temperatures. 

Below listed are the color codes and their specialty of handling water of different temperatures:

Red Pex:

If your drain pipes primarily handle the flow of hot water, your pipes need to be able to withstand the high temperatures and the pipe expansion due to the heat. Red pex pipes are specifically built to handle the flow of hot water and handle the expansion better.

Blue Pex:

If your drain pipes commonly handle the flow of room temperature or cold water, then Blue pex is the best option since it would retain the coolness of the water and prevent heating from outside. 

White Pex:

If your drain pipes have to handle either cold and hot water at times, then red or blue pex would not be suitable for the situation – therefore you need to use white pex which can handle both temperatures of water.

Gray Pex:

Gray pex pipes are no different from white pex as they are also used to handle both hot and cold water.

How to use pex pipe for drain pipe?

Follow the steps below for the installation of pex pipes in drain lines:

Gather the instruments:

You will need a proper cutting tool, crimping tool and couplers.

Insert the crimping ring:

Insert the crimping ring over the pex you want to use for the drain line.

Insert the pipe:

If you’re joining the pipe with another one with a fitting, insert the pipe fully into it.

Use the crimping tool:

Use the crimping tool to crimp the ring near the fitting to hold it firmly in place.

Use a coupler:

To connect the pex with the drain line, use a coupler to connect and insert a crimping ring over it.

Mark and cut old pipes:

Mark and cut old pipes as needed and then use the crimping tool to firmly crimp the rings to the coupler in place.

Final Thoughts

PEX is a popular plastic pipe that may be used for drain pipes in addition to electric and water lines. Pex is also extensively used in appliances such as boilers due to its qualities like flexibility, capacity to hold water pressure while being low in cost, and ease of installation.