PEX pipe is a popular choice for plumbing and water lines these days and for good reason. It’s flexible, easy to work with, and much cheaper than copper.
But one big question pops up all the time is if you can bury it.
The short answer is yes. You can bury PEX. But like most things in home improvement, there’s a right way and a wrong way to do it.
In this post, we’ll show you how to bury PEX without any issues.
Is PEX Rated For Underground Use?
Yes, most PEX is rated for underground use, as long as you protect it properly.
PEX-A and PEX-B are both strong contenders for buried applications. Between the two, PEX-A is more flexible and resistant to freezing, but it can cost a little more. PEX-B is still tough and works well underground, especially when installed right.
You’ll sometimes see PEX labeled for potable water, heating, or radiant floor systems.
For underground use, go with PEX that’s labeled for potable (drinking) water if you’re running a supply line. That kind is safe for long-term contact with drinking water and built to last under pressure.
One thing to keep in mind: PEX can get brittle from UV light. So if you’re storing it outside before installation, cover it up. Sunlight is the enemy here.
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Should You Bury PEX Directly In Soil?
No, burying PEX pipe directly in soil exposes it to a bunch of potential problems.
Rocks can shift. Roots grow. Moisture and movement in the ground can eventually rub away at the pipe. It might not fail right away, but over the years it could wear down, crack, or split.
The better move is to sleeve it or protect it in some way.
That means putting it inside a conduit (like a piece of PVC pipe) or wrapping it in something tough enough to shield it from damage.
This adds a little more to the upfront cost and time, but it’s totally worth it for peace of mind.
How To Bury PEX
Burying PEX isn’t hard, but it does need a little planning. Here’s what that looks like when done right:
#1 Choose The Right Type Of PEX
PEX-A and PEX-B are the top picks for underground use.
PEX-A is the most flexible and has the best freeze resistance. It handles expansion and contraction like a champ.
PEX-B is a little stiffer, but it’s more affordable and still solid for most buried applications.
No matter which one you go with, make sure it’s rated for potable water if you’re running a drinking water line. Don’t use radiant barrier PEX for this unless it’s a heating loop or something similar.
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#2 Use Protective Conduit Or Sleeving
This is one of the most important steps.
You never want to run bare PEX directly through rough soil if you can help it. A length of PVC pipe makes a great sleeve.
It shields the PEX from damage and helps protect against shifting soil, roots, and even rodents. It also gives you the option to pull a new line through later without having to re-dig everything.
If you’re running PEX under a driveway or concrete slab, sleeving is non-negotiable.
#3 Dig To Proper Depth
Depth is all about protection. In warm areas, 12–18 inches deep is usually fine. But in colder regions, you may need to dig down 24 to 36 inches or more to stay below the frost line.
Not sure how deep that is in your area? A quick call to your local building department or a plumber can point you in the right direction.
Deeper trenches offer more stability and help prevent freezing.
#4 Avoid Sharp Rocks Or Debris
Before you lay the pipe in the trench, do a clean sweep. Remove anything sharp, jagged, or hard that might rub against the PEX over time.
This includes roots, broken brick, construction debris, or chunks of hard clay.
Even if you’re using a conduit, it’s still a good idea to clean out the trench first. Clean, soft bedding under the pipe makes a huge difference.
#5 Backfill With Sand Or Soft Soil
After the pipe is laid, you don’t want to just throw dirt back on top of it.
Start by padding the pipe with a few inches of sand, fine dirt, or screened topsoil.
This cushions the PEX and keeps it from getting pinched or scraped.
Once you’ve got that protective layer in place, you can finish backfilling with the regular soil you removed. Just avoid dropping heavy rocks or large clumps right on top of the pipe.
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#6 Avoid Fittings Underground
Always try to run full, continuous lengths of PEX with no fittings buried.
Every fitting you bury is a potential failure point. If one of them leaks, you’ll be stuck digging it all back up just to fix a small joint.
If you need to make a connection, do it above ground or inside an accessible valve box that’s easy to open and repair down the line.
Tips For Burying PEX In Cold Climates
If you live somewhere that sees hard freezes in winter, you’ve got to take a few extra precautions when burying PEX. Freezing water expands, and even a strong pipe can split if it’s not protected.
Here’s how to give your buried line the best shot at surviving the winter:
- Bury it below the frost line for your area
- Wrap the PEX in foam insulation before it goes in the trench
- Consider adding heat tape rated for underground use
- Use a conduit and seal the ends to keep out cold air
- Avoid shallow runs close to the surface where frost hits hardest
- If possible, drain the line in winter to keep it empty
Bottom Line
PEX is totally fine to bury, but it’s not as simple as tossing it in a trench and calling it good.
You need to protect it with a conduit, avoid fittings underground, and use the right type. You also need to dig deep enough to stay safe from frost.
It’s a solid, affordable option for outdoor water lines or long runs between buildings.
Just take the time to do it right, and you’ll have a setup that lasts for years without digging it all up again next season.
FAQs
Can You Use PEX Under Concrete?
Yes, but you need to be extra careful. Always sleeve the PEX in conduit when running it under concrete slabs or driveways.
Concrete expands, contracts, and holds cold – none of which are friendly to bare PEX. The conduit protects the pipe and makes it easier to repair later if needed. Also, insulate it before placing it under concrete.
What Do Plumbing Codes Say About Burying PEX?
Most plumbing codes allow buried PEX, but with conditions. It must be rated for underground use and protected by sleeving when going through concrete or rough soil. Some areas require conduit by default.