Informational · Installation Tips · Maintenance ·Feb 19, 2025

Underground PEX Pipe: A Comprehensive Guide for Outdoor Boiler Owners

At OutdoorBoiler.com, we're dedicated to helping you get the most out of your outdoor boiler. For maximum energy efficiency, reduced fuel costs, and a comfortably warm home, effective heat transfer is essential. This is one of the reasons why we often recommend the underground PEX pipe that has become the default standard in running outside boiler systems to your home and outbuildings. In this blog, we will cover everything you need to know about this crucial element and how it helps in overall energy efficiency.

What is PEX Pipe and Why is it Ideal for Outdoor Boilers?

PEX (cross-linked polyethylene) is simply a really tough and flexible plastic tubing that has changed the game for hydronic heating. This is just one of the many reasons we consider PEX a massive step up from copper or metal piping in outdoor installation. Its flexibility allows it to expand and contract with temperature changes, and helps ensure you are not experiencing significant heat loss.

Outdoor Boiler best partnered with PEX Pipe.

PEX stays a very sensible alternative for better energy efficiency. If you want someone to install it, just search for "boiler installation near me".

Burying PEX pipe when making the connection to your outdoor boiler is going to provide a life expectancy of at least 50 years, if done properly. It stands up to high heat (up to 200°F) while retaining some flexibility when the temperature is frigid — the best freeze protection. Allowing these materials to be used for transferring from

your outdoor boiler to your home without losing as much heat and putting out maximum energy efficiency.

Types of PEX: Understanding Your Options

There are three main kinds of PEX pipe, and they're all made a little differently. Your choice can impact the overall energy efficiency of your system.

PEX-A (Peroxide Method)

This is the most flexible PEX you can get.
It can handle the highest temperatures and pressures.
It has great "memory," meaning it tries to go back to its original shape when heated.
It costs more than the other types.

PEX-B (Silane Method)

It's a little stiffer than PEX-A.
It's more affordable.
It's really good at resisting chlorine.
It has good pressure ratings.
A lot of people use it for regular home plumbing. It can also be used for outdoor boilers

PEX B tubing has the highest bursting pressure among the three types of PEX. This is the reason why although PEX-B tubing is less flexible and has a lower cross-link ratio than PEX-A, it is the ideal choice for burying and it is also cost-effective.

PEX-C (Electron Beam Method)

This is the cheapest PEX option.
It's stiffer than PEX-A and PEX-B.
It can't handle as much pressure.
It might crack more easily when it gets super cold. We don't generally recommend this type for outdoor boiler applications, because freeze protection is paramount.

For outdoor boiler installations, we typically recommend PEX-B due to its excellent flexibility and cold weather performance, providing superior freeze resistance in addition to contributing to overall system energy efficiency.

This highest bursting characteristic of PEX B makes it ideal for burying tubing that may be exposed to freezing conditions. Its non-corrosive substance and a lower likelihood of chemical leaching make PEX-B a more viable choice.

To learn more about which type of PEX should you use for your outdoor boiler, read this article.

Benefits of PEX for Outdoor Boiler Systems

Durability and Longevity

One of the best feature of PEX pipe is that it is rust-resistant and will not scale or corrode. It won’t rust or develop pinhole leaks like metal pipes tend to do, so you can rely on it to last for years. As a result, your outdoor boiler system is energy-efficient in the long run, with minimal repair or replacement requirements.

Flexibility and Freeze Resistance

One of the best things about PEX for outdoor use is that it can stretch when water freezes, providing essential freeze protection. The University of Minnesota Extension did some research that showed PEX can stretch up to 10% when water freezes and then go back to its normal size without getting damaged. That’s a lifesaver for outdoor boilers in cold areas!

Energy Efficiency

If you insulate your underground PEX pipe properly, you can keep heat loss to a minimum as it travels from your outdoor boiler to your house. The Department of Energy says that insulated PEX can keep water temperature steady over long distances, which makes your whole system more efficient and uses less fuel – directly improving energy efficiency.

Cost-Effectiveness

While it might cost more upfront than some other options, insulated underground PEX pipe pays for itself because:

It loses less heat (reducing heat loss).
It uses less fuel (improving energy efficiency).
It doesn't need as much maintenance.
It lasts longer.

Installation Best Practices

Trenching and Preparation

Dig trenches at least 18-24 inches deep (below frost line in your region)
Ensure a smooth, rock-free bed to prevent damage
Maintain a slight slope for drainage and air purging
Consider adding a layer of sand for additional protection

Insulation Considerations

Pre-insulated PEX pipe is available with various insulation thicknesses, typically featuring:

Closed-cell foam insulation
Protective outer jacket
Vapor barrier to prevent moisture intrusion

Connections and Testing

Use proper PEX fittings designed for outdoor applications
Follow manufacturer guidelines for connection methods
Pressure test the system before backfilling
Document your pipe layout for future reference

Maintenance and Long-Term Care

PEX is pretty tough, but doing some regular maintenance will help it last as long as possible and maintain optimal energy efficiency.

Leak Detection

Keep an eye on the system pressure.
Watch out for any sudden drops in efficiency.
You may want to add a leak detection system that will alert you early if there’s a problem.

Winterization

If you're going to shut down the system for the winter, make sure you have enough antifreeze in it to provide freeze protection.
If it is very cold, keep the water circulating.
Follow the manufacturer's recommendations for your specific climate.

System Longevity

If installed and maintained properly, PEX pipe systems can last 50 years or longer. Regular systems checks and monitoring water quality will optimise the investment potential and maintain the efficiency of energy over the long term. Search “boiler installation near me” for skilled maintenance providers.

Conclusion: A Smart Choice for Efficiency and Reliability

We at Outdoorboilers.com believe that an underground PEX pipe is the best way to connect your outdoor boiler to your indoor heating system. Because of its ability to be molded to any shape, and since it's tough and strong, it's highly effective for homeowners who want their outdoor boiler systems to withstand the test of time, economize on heat-loss and capitalise on energy-efficiency.

Invest in a high quality underground PEX pipe and install it properly, and you will enjoy consistent and efficient heat from your outdoor boiler for years. This will help you get the most efficiency possible out of your energy to reduce heat loss, and get the best freeze protection. When seeking help to get your system up and running, don’t hesitate to CONTACT US so that we’ll be able to assist and support your needs.

FAQs: Underground PEX Pipe for Outdoor Boilers

Why should I choose an insulated PEX pipe for underground water lines?

Specially insulated PEX pipe minimizes heat loss in transit to produce more efficient systems across the board, lowering fuel costs. Insulation also protects pipes from freezing, mechanical damage, and ground moisture, increasing the longevity of the system.

How does insulated PEX pipe prevent freezing?

PEX’s innate flexibility enables it to expand when water freezes rather than rupture. That gives a good degree of freeze protection when coupled with decent insulation. Clinches are usually used in extreme climates and the glycol-based antifreeze solution can be added to the system as well for security.