How to Run Plumbing Pipes through Joists
If you need to run plumbing pipes through your home, it is important that you know what you need and how to do the job without any problems that might cause damage to your walls and floors. Here is a guide for running the pipes through joists.
Step 1 - Understand Your Home
Make sure that you are a very familiar with the structure of your home. This way you can make a plan for the new plumbing that is easy to follow while being able to locate any existing plumbing lines running through your home.
Step 2 - Prepare for a Toilet
If your installation is connected to a toilet, it is important that you have at least a three inch drain. This can only be installed if the wall studs are 2x6's or bigger. If they are 2x4's, the pipe will have to be two inches.
Step 3 - Understand the Joist Slopes
When you run your pipes through a joist, you will have to be careful with your work. The holes will have to follow a straight line that goes across the floor and has to either go up or go down so the pipe has a slope. The slope should be about 1/4" for each foot of pipe.
Step 4 - Cut the Holes
You need to make the hole you cut big enough for the pipe to have a little bit of room to wiggle. If it is a 3 inch pipe, you will need to take a drill and your reciprocating saw in order to make the hole 4 1/4" x 10". This will go through the bottom plate of the room you are in and also through the top of the room that is below you, if you have a two story home or a basement. When this is complete, you will have to cut out a 10" x 2' section of the floor.
Step 5 - Install the Fittings
The next thing you will do is assemble the fittings and put them on the top of the drainpipe. Make sure they are going in the right direction. Your drainpipe needs to be somewhat longer than required. That way you can cut it down to the size later. Take the pipe and push it down and through the hole.
Step 6 - Make Adjustments
It might turn out that you will need to make a hole in one of the walls in the room above or the room below you in order to guide the venting pipe up to where it needs to go. If the pipes are going up into the attic, you might be able to take the venting pipe over and tie it to the vent that is already there. If you can't do that, try to drill a hole in the ceiling of your attic. You will need to have a roofer come over and use a roof jack for the venting pipe.
Take straps that come with the piping and use the straps to anchor your drainpipe. Now cut an opening in the ceiling for your venting pipe. If you have a 1 1/2" venting pipe, you need a 2 1/2" hole for the pipe to go through. Take the pipe and push it up the hole and then into your attic or room that is above you.