How to install the construction plumbing

July 10, 2019Blog Standard

The term “construction” when applied to plumbing, means placing all pipes in a new house without making the connections. Contractors usually do the building plumbing while the house is in the structure stage because that is when it is easier to place the pipes through the walls and floors. The home builder can save you a lot of headaches by making a diagram of the water supply and drainage systems, and check them with a certified plumber to make sure there are no code violations before installing.


The water system

  • Make a diagram of the water supply system, showing all angles and pipe sizes exactly how you intend to install them. This will save you many trips to the hardware store by making sure you have enough piping and all the right connections at hand.
  • Use “L” or “M” type copper pipe, or “Schedule 40” PVC pipe if local codes permit. Use tuber inch pipe for all main supplies and ½ inch for branches to individual appliances.
  • Make all the solders in the copper with lead-free material. Clean the pipes thoroughly, spread flux at both ends of the connection and heat the pipe with the propane torch. When the flux begins to smoke and bubble, remove the heat and touch the tip of a solder bar to the connection, allowing the material to slide into the joint.
  • Arrange the water lines through holes previously made in the uprights. Make sure that these holes are slightly larger than the pipes and that they are located at least one inch from the front of the studs to avoid punctures of screws or nails.
  • All pipes that will leave the wall to connect with appliances must be securely secured to the stud with metal tape.

The drainage system

  • Make a diagram of the drainage system showing all the lines of waste and discharge, and all the angles exactly as you plan to install them.
  • It uses Schedule 40 ABS pipe for the drainage system. Make sure that all installed pipes have a slope of 1/8 to ¼ inch per running foot.
  • Connect the ABS pipes by gluing them with ABS pipe glue. Use the brush that comes with the glue can to spread it on both sides of the connection. Slide the pipes one inside the other, making sure they are fully seated, and give them a small twist so that the glue spreads evenly.
  • It uses a 2-inch spout for sink and shower drains, and a 3-inch spout for toilet drains. Where three or more lines come together in one, use a 3-inch pipe for the common line. Download all lines in a vertical pipe that goes through the roof or walls, or connect with one that does.
  • Arrange drainage lines laterally through the uprights by notching them with a reciprocating saw, taking care not to weaken the upright to the point that it no longer serves as a support. Cover the open side of the notch with a metal plate to prevent the screws or nails from pricking the pipe. Use metal tape to hang the drainage lines from the floor joists in the basement or the bottom of the house. Make sure to maintain the required slope in all pipes.


  • It is a good idea to install a drain at the lowest point of the water line so that it can be easily drained from the system when repairs are required.


  • Use pressurized air to verify that the water system has no leaks before making the final connections. The welds are very difficult to redo once there is water in the line because it vaporizes and prevents the pipe from reaching the temperature sufficient to melt the weld metal.

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