Concentric PP/Plastic X3 Push-fit system
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CoxDENS® with CONNEXT® X3 

CoxDENS® with CONNEXT X3 is a concentric plastic/PP flue gas system with the patented CONNEXT X3-connection. CoxDENS® with CONNEXT X3 is especially designed for condensing heating appliances.

connext x3
connext x3

Safe with concentric

That is Cox Geelen’s vision into which this new innovative system perfectly fits. Carbon monoxide (CO) is an underestimated and unrecognized danger. Carbon monoxide poisoning is often caused by modern heating appliances. To reduce the risk of such poisoning, it is advisable to install a concentric flue gas system.
connext x3
connext x3

Product advantages

A plastic flue gas pipe expands more than a metal pipe when heated. Our concentric system takes account of this expansion. The expansion of the inner pipe will not lead to the break-up of the concentric flue gas pipe. In the unlikely event of a leak in the flue gas pipe, the flue gases entering the combustion air supply pipe are routed to the combustion heater. An excessively high content of recirculated flue gas will cause the boiler to shut down. This prevents a dangerous situation for residents.

► A concentric system thus adds an additional barrier for any carbon monoxide formed, and prevents hazardous gas entering the living space of the home.

connext x3
connext x3


  • Available in Ø 60/100 mm in the color white (RAL 9016). 
  • PP flue gas pipe. 
  • The outer pipe is made of plastic. 
  • The inner pipe is centered in the outer tube 'tube-in-tube' by the patented CONNEXT X3 Push-Fit coupling. 
  • Easy to shorten. 
  • The flue gas pipe is surrounded by air, an additional safety barrier. 
  • Suitable for overpressure (class H1). 
  • CE tested in accordance with EN 14471:2013 + A1:2015
connext x3
connext x3

Product range

  • Pipes in lengths 250, 500 and 1000 mm
  • Bend 87° and 45°
  • Bend 87° with 2 measuring points
  • Inspection piece
  • Measuring point
  • Adapter 80/80-60/100 mm
  • Fire resistant wall plate with fire protection seal
  • ECONEXT® plastic roof terminal and wall terminal

► A concentric flue system provides most safety!

connext x3
connext x3

Fire resistant wall plate

Cox Geelen introduces round fire resistant wall plates with integrated fire proof wall plate and fire protection seal. These innovative CoxDENS® plates were designed for connection to flexible as well as concentric flue gas systems. These revolutionairy wall plates neatly cover an opening in the wall and also provide a fire and carbon monoxide safe situation in the home. Why round? Mounting can not go crooked and the slope of 3° is included in the design read more.


The CoxDENS® with CONNEXT® X3 flue system is designed for the modern condensing boiler.


The CoxDENS® with CONNEXT® X3 flue system can be completely recycled at the end of its life cycle.

Download for more information: CONNEXT® X3 brochure.

We recommend the film 'Carbon Monoxide - Understimated and misunderstood danger', recommended by the Dutch Safety Board.

Link to CoxDENS® PP/Alu with CONNEXT® X7.

Call our sales support +31 43 40 99 500.

Mail to or request a free quote here.