Explaining Five Different PEX Connection Methods

via PEX

The pros and cons of five different PEX connection methods 

With PEX becoming the primary plumbing product for residential construction, and commercial construction beginning to install the pipe in certain applications, it’s important to know the five most commonly used connection methods for the piping system as well as the positives and pitfalls of each. 

Crimp 

How it’s done: 

  1. Slide a copper ring onto the pipe and then insert an ASTM F1807 (metal) or ASTM F2159 (plastic) fitting into the pipe. 
  2. Slide the ring back toward the end of the pipe where the pipe and fitting overlap (this location varies with each manufacturer, so be sure to follow the manufacturer’s instructions). 
  3. Compress the ring with a crimp tool until the tool stops. 
  4. Use a go/no-go gauge to verify a proper connection (loose crimps = leaks; crimps that are too tight = fitting or pipe damage). 

Pros: Fast and easy to learn, quick to install, relatively inexpensive, tools and products readily available at a variety of retailers 

Cons: Crimping works against the “shape memory” of PEX (which always wants to return to its natural shape). Without the confirmation of a go/no-go gauge, a loose crimp can potentially lead to leaks because the pipe is constantly pressing against the ring. Additionally, the smaller internal diameter (ID) of the insert fitting reduces system flow and also opens up the potential for dry fits. 

Clamp 

How it’s done: 

  1. Ensure the clamp tool is properly calibrated. 
  2. Slide a stainless-steel ring onto the pipe. 
  3. Insert an ASTM F2098 fitting into the pipe. 
  4. Position the ring back over the pipe (position depends on the manufacturers recommendation). 
  5. Compress the ring with a clamp tool until the tool stops. 

Pros: Fast and easy to learn, quick to installrelatively inexpensive, tools and products readily available at a variety of retailers, easy to disassemble (in case the fitting needs to be removed), only needs one tool for any size connection (no need to purchase separate heads for different pipe sizes) 

Cons: Like crimping, clamping also works against the “shape memory” properties of PEX, smaller-ID fittings restrict flow, tool calibration is imperative to a proper connection (miscalibrated tools can result in leaks or damage to pipe and/or fittings) 

Push-to-connect 

How it’s done: 

  1. Insert a stiffening sleeve into the pipe (some manufacturers require an insert stiffener and some do not; be sure to follow the manufacturers’ installation recommendations). 
  2. Push the pipe into the fitting. 

Pros: Fast and easy to learn, quick to install, no special tools needed, easy fitting removal (if necessary) 

Cons: Higher cost compared to clamp and crimp, fittings must be wrapped in an impermeable material prior to direct burial in soil, freeze tests and pull tests show these PEX connections are more susceptible to failure (because PEX is more malleable than metal, the fitting’s teeth can slide off the pipe) 

Expansion 

How it’s done: 

  1. Slide a PEX expansion ring over the end of the pipe. 
  2. Expand the pipe with an expansion tool until the pipe reaches the head of the tool. 
  3. Insert an ASTM F1960 fitting. 

Pros: Fast and easy to learn, quick to install, maximizes the “shape memory” of PEX (pipe and ring are always pressing down onto the fitting), larger-ID fitting improves flow, impossible to dry fit, approved for direct burial in soil as well as concrete, eliminates the need for go/no-go gauges or tool calibration 

Cons: Sealing time takes longer in cold weather (below 40°F), products and tools only available through professional plumbing supply distributors to trained installers 

Expansion with compression 

How it’s done: 

  1. Slide a metal sleeve onto the pipe far enough to leave room for inserting the fitting. 
  2. Using a special tool with an expander head on one side and compression jaws on another, make one expansion with the pipe then rotate the tool to make another expansion. 
  3. Insert an ASTM F2080 fitting. 
  4. Turn the tool around to use the compression jaws to compress the sleeve over the pipe and fitting. 

Pros: Immediate pressure testing, no issues with cold temperaturesbetter system flow 

Cons: Two-step process can take more time, can be hard to maneuver the tool into tight spaces to make the compression portion of the connection, potential for injury due to pinch point area near the compression jaws, tools and products only sold through professional plumbing supply distributors 

One last word of advice: Stick with one brand 

While understanding the benefits and challenges with each connection method is importantit’s most important to stick with one brand. Why? Because most PEX manufacturers offer a warranty with their pipe and fittings (some up to 25 years). Once you start mixing brands for the pipe, fittings, sleeves and rings, that warranty may be greatly reduced or void. 

The last thing you want is to be left holding the bag if you have a service or warranty issue and the manufacturer can’t help because you’ve mixed brands. 

If you’d like to learn more about PEX and the manufacturers for North America, visit the Plastics Pipe Institute website at plasticpipe.org or the Plastic Pipe and Fittings Association website at ppfahome.org. 

About the author:

Kim Bliss is the content development manager at Uponor. She can be reached at [email protected].