Should you insulate PEX underground?

Author: Dante Price  |  Last update: Monday, December 22, 2025

In colder climates, insulating PEX pipes can help prevent the water inside from freezing, which could lead to burst pipes. On the flip side, in hot and humid environments, uninsulated cold water lines may sweat, leading to potential issues like mold growth or water damage. Insulation can help mitigate these risks.

Is it code to insulate PEX?

PEX tubing does not provide any significant thermal insulation properties and would not meet code requirements without additional insulation.

Do underground water pipes need to be insulated?

All newly installed water pipes will need to be insulated before they are buried. It's a requirement stipulated by the local water authority. The leading product for underground use is Armaflex Tuffcoat.

Should PEX be sleeved underground?

Can you bury PEX? Yes, you can bury SharkBite PEX-a and PEX-b pipe in most applications, as it's approved to AWWA C904, which covers PEX pipe in regard to burial. Be sure to check with local, city or state codes to see if the pipe needs to have sleeves or any type of protective burial for your area.

Do I need to insulate PEX underground?

In colder climates, insulating PEX pipes can help prevent the water inside from freezing, which could lead to burst pipes. On the flip side, in hot and humid environments, uninsulated cold water lines may sweat, leading to potential issues like mold growth or water damage. Insulation can help mitigate these risks.

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How long will PEX last underground?

PEX: Due to its flexibility and durability, PEX piping should last at least 50 years. PVC / CPVC: Under typical conditions, these pipes should last up to 100 years. Keep in mind that PVC pipes are often used for drainage because extreme heat can damage them.

What is the best insulation for underground water lines?

It is important to use insulation that is suitable for underground conditions to prevent moisture absorption and degradation. Polyethylene foam insulation, such as Armaflex, is a common choice for underground pipe insulation due to its resistance to water and moisture.

At what temperature do underground water pipes freeze?

Your pipes are at risk of freezing any time temperatures drop below 32°F. However, it's much more common for pipes to freeze when temperatures dip below 20°F. The longer the weather remains below freezing, the more likely it is your pipes can freeze if not properly protected and winterized.

Why don t underground water pipes freeze?

Underground pipes are heated by the earth, so they don't usually freeze, but it can happen. The depth of the pipes and the piping material help prevent freezing. When temperatures are around 20 degrees or lower for long periods of time freezing may be an issue.

How deep should insulated PEX be buried?

Consult with local building codes but generally a 24" depth is required for direct bury electrical wire. Where the PEX will protrude from the ground, a depth of 4' will be required to have the PEX have enough bend radius to protrude being perpendicular to the ground.

Will PEX freeze if insulated?

Insulate your pipes: Insulating your PEX pipes can help to keep the water inside them from freezing. You can use foam insulation sleeves or tape to wrap around the pipes.

Where should you not use PEX?

Caution: Do not use Uponor AquaPEX piping to connect the tub and shower valve to the tub downspout as this may create excessive back pressure in the valve, causing it to remain slightly open. I have always known pex to outflow copper...

What is the best insulation for PEX pipe?

Insulating your PEX is a very vital step in making your PEX last for a long time. And there is no better way to insulate your PEX than using radiant barrier insulation. Other types of pex insulation would promise you many things but only radiant barrier insulation will deliver at a very affordable price.

What are the tips for burying PEX?

If using a PEX pipe underground, bury it at least 12 to 18 inches below the frost line. The temperature is warmer just a few feet below the surface. In a cold region, the frost line may be three or feet down, so this is an important consideration.

Why does PEX pipe get pinholes?

Accelerated chlorine degradation can result in pinhole leaks in PEX pipes and fittings relatively early in their expected life. Abrasions or cracks that develop through the pipe wall or “popcorning” discoloration of the surface of PEX pipe are signs of chlorine degradation.

What is the best pipe insulation to prevent freezing?

Use foam rubber or fiberglass sleeves to help decrease the chances of freezing. Insulation can help keep the pipes closer to the temperature of the water inside the pipe, but it does not add extra heat to the pipe and unfortunately will not prevent freezing if the pipe is exposed to prolonged freezing temperatures.

How deep should pipes be buried to prevent freezing?

The IPC and IRC also state that all water and sewer lines must be at least 6 inches below the typical frost level for the area to help ensure that the pipe can't freeze.

Should you drip all your faucets?

Set faucets to a small, steady drip rather than a stream to conserve water while preventing freezing. Drip the faucet farthest from your home's main water valve. “You don't have to drip them all—one or two is fine,” Sperlich told USA TODAY.

How to keep a buried water line from freezing?

If you have a buried water line that is at risk because of fresh backfill or thin cover, you can add insulation on top of the ground in the form of hay, leaves, or even snow piled over the water line.

What is the R value for PEX pipe insulation?

R-Value Requirements

For PEX tubing, higher R-values provide better insulation. Cold climates typically require R-values of 3 to 4 for indoor pipes and 5 to 6 for outdoor or unheated areas. Warmer regions may suffice with R-values of 2 to 3.

Does underground pipe need to be insulated?

Underground piping systems should be protected with an insulation system that can meet the moisture and corrosion resistance requirements of direct burial to be able to provide long-term insulation efficiency.

Is PEX ok to run underground?

Yes, PEX pipes can be buried underground. However, it's important to follow local building codes and guidelines to ensure compliance and the longevity of your plumbing system. To ensure optimal performance and protection against external factors, it is essential to bury insulated PEX pipe at the appropriate depth.

Will PEX pipe freeze underground?

It depends. While pipes themselves don't freeze, the water inside of them does when the area around the plumbing reaches the freezing point. Even if the temperature outside is 32 degrees, pipes underground, for instance, may not be unless it's lower than 32 outside.

Do plumbers prefer PEX or copper?

Copper is usually preferred for water supply lines and heating systems but plex is most often used for drain or waste lines because copper corrodes over time. Ultimately, it's up to the homeowner to decide where to spend the construction budget.

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