How to install plumbing

The term “work” when applied to plumbing, means placing all pipes in a house new without making connections. Contractors normally do plumbing work while the house is on the stage of the structure because it is there when it is easier to lay the pipes through walls and floors.


The water system

  1. Draw a diagram of the water supply system, showing all pipe angles and sizes exactly as you intend to install them. This will save you many trips to the hardware store by making sure you have enough tubing and all the correct connections at hand.
  2. Use “L” or “M” copper pipe, or “Schedule 40” PVC pipe if your local codes allow. It uses ¾-inch tubing for all major supplies and ½-inch for branches to individual artifacts.
  3. Make all the welds on the copper with lead-free material. Clean the pipes thoroughly, scatter 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 with the tip of a welding rod the connection, allowing the material to slide into the joint.
  4. Lay the water lines through holes previously made in the uprights. Make sure these holes are slightly larger than the pipes and that they are located at least one inch from the front of the uprights to avoid punctures of screws or nails.
  5. All pipes that will come out of the wall to connect with appliances must be secured firmly to the stud with metal tape.

The drainage system

  1. Draw a diagram of the drainage system showing all lines of waste and discharge, and all angles exactly as you plan to install them.
  2. Use Schedule 40 ABS tubing for the drain system. Make sure all installed pipes have a 1/8 to 1/4 inch pitch per foot.
  3. Connect the ABS pipes by gluing them with ABS pipe. Use the brush that comes with the glue can to spread it on both sides of the connection. Slip the pipes into each other, making sure they are fully seated, and give them a small twist so the glue spreads evenly.
  4. Uses 2-inch pipe for sink and shower drains, and 3-inch for lavatory drains. Where three or more lines are joined in one, use a 3-inch pipe for the common line. Discharge all lines in a vertical pipe that goes through the ceiling or walls, or connect with one that does.
  5. Lay the drainage lines laterally through the uprights by notching them with a reciprocating saw, being careful 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 screws or nails from pinching the spout. Use metal tape to hang the drain lines of the floor beams in the basement or the bottom of the house. Be sure to maintain the required slope on all pipes.

Tips & Warnings

  • 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 due.
  • Use pressurized air to verify that the water system does not leak before making the final connections. 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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