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How to Use Pex With Boiler

Mitzi Saltsman

Pex tubing is a flexible plumbing material designed in the 1960s. It was introduced to the United States in the 1980s, but recent sales indicate an increased popularity. As radiant floor heating sales increase, Pex tubing and the use of boilers increase as well. The Pex material is made to be strong, yet pliable, making it ideal for pipes that need to bend around and throughout a house. Since the boiler needs to heat the water to a temperature of 180 degrees, it is not suitable for use in the kitchen or bathrooms.

Flexible Pex tubing attaches easily to a boiler.
  1. Place the Pex tubing throughout the house or area you are planning to heat. The boiler is the starting point and ending point for the tubes. A radiant heat system is enclosed, so the Pex tubing will begin at the boiler, circulate throughout the floor, and end back at the boiler. The tubes and boiler will not be hooked together until after the tubes are placed in the floor. Concrete is poured on them to create the floor. It is also possible to snake the tubes throughout the floor with specially insulated floor mats that hold the tubes in place and a subfloor that can be built on top of the tubes.

  2. Bring the Pex tubing to where the boiler will be placed. Start and end placing the tubes with about three feet of tube extending out of the floor. The boiler is hooked up to water main pipes to access water that the boiler heats. The water will circle through the floor and end up at the boiler again. The extra tubing is left out of the floor to reach the valves needed at the boiler.

  3. Attach the fittings to the ends of the Pex tubing with a standard Pex crimping tool and Pex mechanical or compression fittings. Half of an inch of Pex tubing is used in radiant heating systems for a home. The mechanical fitting is a copper ring that is fit over the end of the Pex. The fitting is inserted in the end of the tube and they are crimped together with the crimping tool. Expansion fittings are inserted into the tube with a special tool that expands the Pex to allow the fitting to be inserted in its end. A compression fitting is a specialized fitting that is recommended for larger commercial jobs. Chemicals or glue cannot be used with Pex tubing.

  4. Attach the Pex to the correct valve for the boiler you are using. The fittings can be adapted and checked for compatibility on standard charts. Choose the fitting needed for your boiler.