When it comes to outdoor wood boiler systems performance, reliability, and safety are a must. What is often ignored by installers is the PEX fitting which is a very critical component of your hydronic heating system. These small connectors play a large role in the efficiency and longevity of your setup. A single leak or a low quality fitting can bring your system to a stand still and cause expensive water damage.
In this depth guide we will break down for you everything you need to know about PEX fittings, how they work, what makes a quality product and how to choose the right one for your outdoor boiler application. Whether you are a do it yourself or a professional installer this guide will save you time, money, and stress.
What is a PEX Fitting?
PEX (cross linked polyethylene) is a flexible yet very durable plastic used in water supply lines and radiant heating systems. PEX fittings are the connectors that join pieces of PEX tubing together or which the tubing is connected to valves, manifolds and other system components. Fittings come in a variety of materials (brass, poly, stainless steel) and styles (crimp, clamp, push to connect, expansion). What you put in will determine system compatibility, performance and safety. (iFAN Plaumbing, 2023)
Why are PEX Fittings so important in Outdoor Wood Boiler Systems?
Outdoor boilers operate in extreme conditions – cold weather, variable temperatures and long distance underground piping. PEX is the go to material for this type of application because of its freeze resistance and flexibility but without the right fittings the best tubing may as well be useless.
Key functions of PEX fittings in outdoor boiler systems include:
- To give you leak free connections over large distances and at varying temperature.
- Support the structure of the tubing layout.
- To give secure transitions from PEX to pumps, manifolds and heating exchangers.
- To maintain consistent water flow and pressure throughout the system.
Poor quality or incorrect installation of a fitting will lead to leaks, burst pipes or system inefficiencies all of which will end up costing you in repair time and money.
Types of PEX Fittings: What Are Your Options?
Not all fittings are created equal. It is important to choose the right type for your application.
- Crimp Fittings
- Material: Usually brass or poly.
- Installation: Use of a crimping tool and copper rings required.
- Pros: Affordability, wide availability.
- Cons: Precise installation required, over or under crimping causes leaks.
- Clamp (Cinch) Fittings
- Material: Brass or stainless steel.
- Installation: Use of a cinch tool and stainless steel clamps required.
- Pros: Easier install than crimp, more forgiving.
- Cons: May require re-tightening in extreme conditions.
- Push-to-Connect Fittings
- Material: Brass or polymer.
- Installation: Tool free.
- Pros: Very quick and easy, great for emergency repairs.
- Cons: More costly, may not be the best for permanent underground applications.
- Expansion Fittings
- Material: Typically PEX-A compatible.
- Installation: Special expansion tool required.
- Pros: Excellent flow rate, strong lasting connections.
- Cons: More tools and experience required.
You can view the full collection of Outdoor Boiler Fittings HERE.
Material Comparison: Brass vs. Poly vs. Stainless SteelBrass Fittings
- Durable and corrosion resistant.
- Good for high pressure systems.
- Compatible with all PEX types (A, B, C).
- Vulnerable to dezincification in certain water conditions.
Poly Fittings
- Resistant to scale and corrosion.
- More affordable and lighter weight.
- Ideal for chemically aggressive water.
- Durability in high pressure applications.
Stainless Steel Fittings
- Very strong and corrosion resistant.
- Best for high demand systems.
- Great for underground and outdoor boiler use.
- More expensive.
Which is best for you? That depends on your boiler’s specs, installation location, and long term maintenance plans.
Common Mistakes When Choosing or Installing PEX Fittings
To avoid issues and frustration with rework, stay away from these common mistakes:
- Using incompatable tubing and fittings (for example putting PEX-A tubing with PEX-B only fittings).
- Skipping the pressure test post install.
- Failing to properly protect underground fittings with insulation or enclosures.
- Over or under tightening crimp/clamp fittings.
- Using low quality unbranded fittings that fail under stress.
- Improper storage of fittings before use – exposure to moisture, contaminants, or UV.
Ask yourself: Did I pressure test each connection before backfilling? Did I check the compatibility between the tubing and fitting brands? Am I using fittings that are rated for underground and freeze/thaw conditions?
Signs Your Fittings Might Be Failing
Even after installation, stay alert to early warning signs of fitting failure:
- Unexpected changes in pressure.
- Seeing water at joints or in buried sections.
- Not seeing even heat distribution or increased heating times.
- Notice any corrosion or change in color around the fittings.
Routine inspection and seasonal maintenance is key. Don’t wait for winter to reveal a weak spot.
How to Source High-Quality PEX Fittings
With so many options online and in hardware stores, how do you know you’re getting high-quality PEX fittings?
Look for the following:
- NSF/ANSI certifications for potable and radiant heating use.
- Brand reputation – go with the well known players in the hydronic and outdoor heating fields.
- Material grade – stay away from unmarked metals and plastic composites.
- UV and freeze resistance for outdoor and in ground use.
- Warranty or product guarantee.
At OutdoorBoiler.com we test all of our fittings to perform in the special conditions present in outdoor boiler applications. This gives you peace of mind, especially in the dead of winter.
Conclusion: Invest in Peace of Mind with the Right PEX Fittings
Choosing the right PEX fittings for your outdoor boiler system is not a task to take lightly – it is a question of performance, safety, and longevity. The wrong fitting may cause failure of the system, emergency repairs which you may not be prepared for when you need your system the most.
By learning what types of fittings are out there, the variances in materials and the value of proper installation you will be able to make smart, informed decisions that protect your investment.
Don’t settle for second best. Visit OutdoorBoiler.com today to see our range of premium PEX fittings, tools and installation kits which we have designed just for outdoor boiler owners. Have questions? Our tech support team is here to guide you Contact Us – so you can install with confidence and keep your home warm and free of leaks.
Stay warm. Stay prepared. Stay leak free.
FAQS
How long do PEX fittings last?
PEX fittings which are installed and maintained properly may last up to 50 years or more. Their life span is very much a function of variables like water quality, temperature and UV exposure. For best results over the long term proper installation which includes the use of the right tools and adherence to the manufacturers’ instructions is key.
What causes PEX to fail?
The primary cause of PEX failure is the in tube chemical attack which is a result of the chlorine in municipal water supplies. This attack is also made worse by heat and stress.
Is it OK to reuse PEX fittings?
Reusing PEX expansion fittings is out of the question in most cases. For what it’s worth it may be done in a emergency or for a temporary fix. For instance: In the case of a emergency repair until a more permanent solution is put in place.
How to stop a PEX fitting from leaking?
To fix a PEX fitting leak first turn off the water supply. Then based on the type of fitting (crimp, expansion, or push to connect) perform the appropriate action which may be to recrimp, reexpand, or reseat the fitting. If the leak continues out may have to replace the fitting or use a temporary repair like a clamp or sleeve.
Are plastic PEX fittings a good choice?
This is one great feature of the plastic PEX fitting. They don’t tend to leak. As opposed to the brass PEX fitting which has a tendency to weep, you can expect to get out of plastic PEX fitting 10 years of great service without issue.
