How To Run Toilet Drain Through Floor Joist

A toilet drain may seem nothing, but it is one of the most crucial items while building your house. Especially if your home has a suitable joist, this is like drinking water, but if you have complicated flooring, it might be a mess.

Let’s not be negative and discuss how to run toilet drain through floor joist. You have to be specific about where you want to make the toilet line. Think of where you want to add the drain and then start taking the steps that we mention below. You will not only make a suitable drain, but your floor joist will be safe also.

How To Run Toilet Drain Through Floor Joist

Running a toilet drain through floor joist is very common in all USA and CANADA. However, things go out of hand if the calculator or the measurement goes wrong. You see, the floor joist is a susceptible area that receives the weight of the entire floor. To put something there, the measurements should be precise.

We will provide you with the info that will help you step by step to complete the process all by yourself. Make sure you keep all the safety tools alongside you.

Safety Measurements:

  • Hand gloves,
  • Safety glasses,
  • Fast Aid Kit.

Tools necessary for completing the process:

  • Desired size of pipe,
  • Pipe range,
  • Clips (plastic and steel)
  • Glue,
  • Saber saw,

Steps to follow

Whenever you have all of these components, you can start working. Now follow the steps one by one.

  • First of all, see the layout of your house, where the drain pipe is, and how it moves. Do you want to change the direction or not. If you keep the drainpipe as the design, it will be safe, and there will be fewer chances of an accident.
  • Now take a measuring tape and pencil to pinpoint the area where you want to keep the drain pipe.
  • Scale properly with the pencil and keep markings.
  • The best item to use is PVC pipe, and those are cheap and popular. These are reliable and do not break very often. Moreover, these pipes are easy to change if necessary.
  • Now select the size of the pipe. Most of the time, the architecture or the engineer provides a specific size suitable for the house, depending on all other elements.
  • Now take all your tools, wear your safety glasses and gloves. We are about to start the main work.
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  • Take the pipe, put it on the blank space between the joist. Now you will see whether the pipe sits appropriately or not. Now cut the pipe according to your need. You can use a saw or any cutter to complete the process.
  • Now put the pipe over there and take out the saber saw.
  • Use the saber saw to cut the floor with precise size. Remember to mark the area before making a hole.
  • Now you have to keep the pipe perfectly aligned in the middle and use clips to attach the pipe to the surface.
  • Make sure you don’t bolt the pipe too hard. Keep a generous amount of pressure while working on it.
  • After clipping the pipe, you have to align the floorboard with the hole onto the pipe.
  • Before attaching the pipe, remember to cut the hole according to the pipe. You have to keep 5cm extra.
  • Now attach the entire area keeping the floor adjusted with the hole.

You can quickly put a 3-inch pipe through the floor joist following these steps. However, there are situations where you need to change the design. In this case, use your ideas or expertise to get the piple aligned.

Things To Remember While Drilling Holes In Floor Joists For Plumbing

Remember, do not put too much pressure on the board when you think of drilling holes in the floor joists for plumbing. Things to remember while working:

  • Do not put extra pressure on the joists while drilling holes.
  • Make sure you use a saber saw.
  • Do not put glue on the surface you are drilling.
  • You can glue the claps or clips, or you can also nail the clips. However, you have to be careful while resolving the clamps because they can cause cracks.
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Frequently Asked Questions (FAQs)

What is the code for drilling holes in floor joists?

Openings drilled in joists should not be inside 2 inches (51 mm) of the top or lower part of the joist. The distance across any opening will not surpass one-third area of the joist. The codes are 2308 & IRC R502.

Can you put a waste pipe through joists?

Yes, you can easily put a waste pipe through joists. However, the best practice is to avoid using or putting waste pipes through joists.

Does drilling holes in joists weaken them?

If you drill the holes without caution, it can weaken the joists. However, if you keep precise calculations, the joist will not drain.


You searched for the proper instruction, and we think the steps we mentioned are perfect. You will face no complications while following these steps. The main concern is how to run toilet drain through floor joist, well now you know how to do it.

Moreover, you have to keep in mind that the tools we have mentioned are needed. You can always keep extra tools, but these are a must, especially a saber saw. Don’t put too much pressure while drilling a hole and nailing the pipe. If you maintain these, then there will be no complications.

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Along with doing lots of plumbing work, they are usable for other house chores too. From wiping out the spill on the floor to cleaning the dust, bamboo paper towels effectively perform their work. They are effective in replacing regular cloth towels that you often purchase. The natural strength and softest fiber of bamboo make them one of the best sustainable bamboo paper towels.

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