How to Do Plumbing with PEX Tubing


Last year my older home had a serious water leak that resulted in major damage. I didn't want to have to face those repairs again, so I decided to replace the plumbing. After receiving a couple of huge quotes, I decided to see if this was something I could do myself. I researched plumbing how-tos and found information on PEX tubing. It seemed simple enough. PEX is flexible, durable and joins easily. The hardest part of the job was getting certified --- in many areas you can't buy PEX without training and certification.

Things You'll Need

  • PEX tubing -- measure the distance of your installation or repair to determine how much tubing you need
  • PEX fittings -- number and type determined by the job you are doing
  • PEX crimper (unless you use slide on fittings)
  • PEX fitting removal tool
  • Graph paper, pencil
  • Tape Measure
  • PVC type cutting tool or sharp knife
  • Support hangers (match tubing size)
  • Pressure gauge
  • Compressor

How to Replumb a Home with PEX Tubing

  • Obtain PEX certification if needed. Many areas require certification to purchase PEX and pass county inspection. The class for certification is short (usually about an hour) and covers how to apply fittings correctly and to properly use PEX tubing.

  • Planning the job is the most important and time-consuming part of the process. If you are doing a complete replumb, draw a basic outline house plan and determine where all plumbing fittings will be. Include the water heater, the cooling system if it uses water, bathrooms, the kitchen, laundry rooms and outside spigots (and any other areas that will need water). Note each fixture on your house plan.

  • After you decide on all fixtures, plan out the path the water will take. For most fixtures, you will need both hot and cold lines. Exceptions include the toilet, refrigerator water dispenser, and dishwasher if plumbed separately. Determine the path that uses the least number of fittings on your PEX tubing. Keep in mind that PEX is very flexible and does not need fittings to make a diagonal or angled run. Depending on how your floor plan is set up, you can go in one straight line, or you can tee off in different directions.

  • Once the path is set, begin measuring. Measure each run, making sure you include the run up to the fixture. Note the size of PEX tubing you wish to use for each fixture. Some bath faucets need a ¾" tube, while most bath sinks and toilets need ½". It helps to make a list of each measurement, with columns for each size you need. Once you have the measurements added, you know how much PEX tubing you need in each size. Some hardware and plumbing supply stores sell PEX by the foot, and some sell in 50- or 100-foot rolls. This is also the time to determine all the fittings you will need to join the Pex tubing.

  • Cut your PEX ahead of time if you are very sure of your measurements, or cut it as you go. Start at the water inlet, and proceed in the order determined by your house plan. Attach the PEX tubing to the inlet and unroll enough to get to your first fixture. Note: To save time, you can do hot and cold at the same time; just make sure you keep the hot on the left and the cold on the right.

  • If you are working in crawl space, attach support hangers as you run the PEX tubing. If you are working in an attic, tack PEX tubing to the rafters with support hangers.

  • When you get to each fixture, use the appropriate PEX fitting (90-degree, 90-degree reducer) to run the next tube into the wall where the fixture goes. You should already have holes drilled through the subfloor.

  • Once you have run PEX tubing to all your fixtures, make sure each one is closed off and perform a pressure test. Attach a pressure gauge, and introduce pressure into the lines with a compressor. The pressure should remain the same overnight.

  • If pressure holds, you may either call for inspection (if necessary) or introduce water into the system. If pressure does not hold you must find the leak(s). The easiest way to find leaks during a pressure test is to use a spray bottle with a soapy solution. Spray on each joint and if a particular joint has a leak it will create a lot of small bubbles.

  • Rough plumbing is complete at this point. If you have passed inspection, attach necessary fixtures, repair drywall as necessary and enjoy your newly plumbed home.

Tips & Warnings

  • Warm your PEX tubing a bit to straighten. Rub with your hands or hold in front of a heat vent. Make sure your ends are round after cutting --- if they are flattened it is more difficult to apply fittings. Make sure your fittings are attached securely and properly. Inspect your plumbing on a regular basis to prevent small leaks from becoming serious problems.
  • PEX tubing can not withstand UV exposure. Keep your tubing covered outdoors. PEX tubing can not be buried directly; you must run PEX inside a PVC, galvanized or copper line.

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