Can I Install Bathroom Vanity Plumbing Through the Floor? ANSWERED

You might assume that plumbing for a bathroom vanity must go through the wall. After all, how else could you get water and drain pipes into it? However, there’s in most cases no rule that forbids you from installing your vanity plumbing through the floor instead. 

Example of drains and water pipes that are installed through the floor. Image by PlumbingInstantFix. All rights reserved;

 In fact, doing so has some advantages. If you’re considering this option and aren’t sure if it would work in your home, here are a few things to know before giving it a try. Check your local plumbing code before you proceed.

For the water supply lines, it doesn’t matter if you run them through the wall or floor. Water is under a lot of pressure so it can often travel vertically for a short distance. If you have water pressure problems or the water has to travel for a long distance, you can consider adding a water pump.

The main challenge is installing the drains as these have to be installed correctly to avoid clogs. Let’s study this in more detail.

Pros of Installing Vanity Plumbing Through the Floor

There are a couple of advantages to plumbing your bathroom vanity through the floor. Most obviously, you’ll save yourself the work of cutting a hole in the wall. 

Secondly, you might have easy access to the plumbing should you ever need to make a repair. This is because some ceilings are easier to open up than walls.

It can give the bathroom a cleaner look and open up some space behind the vanity. This is especially the case if the water supply pipes also come out of the floor.

If the drain is already running through the floor, it is quite easy to install a new one that does the same.

It can be easier to update the floor plan when the drains run through the wall as it is easier to remove or add walls in that case.

If you plan to work on the walls (for example add electricity or ethernet cables), it is also a good idea to install the drains through the floor. In this way, you make sure that you don’t drill in them while you are installing new cables. 

Cons of Installing Vanity Plumbing Through the Floor

While plumbing your vanity through the floor does have some advantages, it also has some downsides. 

This can be harder to do on the ground floor as the concrete slab can be quite hard to drill into.

On the first or second floor, this is often easier but you might need to reinforce the floor if you’re routing the pipes under it. You can do this by adding a plywood subfloor underneath the other flooring. The stability of the floor shouldn’t be affected by drilling into it.

Drains have to go in at a certain angle. This makes sure that the water and dirt flow away instead of getting stuck in the drain. The water shouldn’t flow too fast though as this can result in noisy pipes. It can also lead to clogs as the water can’t take the dirt with it. 

Getting this angle right can be harder if you need to install the drain through the floor.  Plumbers often use software to determine where they should install the drains. This makes sure that everything is connected properly.

Drains also have to be vented to make sure that gravity can push the water down. This is mainly an issue in big buildings and is often less of an issue in a standard home.

 Finally, you’ll need to be careful to avoid hitting the pipes when you lay the flooring.

Sinks need a bottle trap or p-trap to function correctly. They can be harder to install if you have to run the drain through the floor.

When to Use the Wall Route

Even though plumbing through the floor has some advantages, it’s not always the best option. The wall route will generally be easier, cheaper, and faster for a number of reasons. 

First, you’ll need to do some heavy lifting when plumbing through the floor, whereas you can easily knock a hole in the wall as they are generally made out of softer materials.

Secondly, wall routing is easier because you won’t need to worry about reinforcing the floor. 

Drains are often connected. If you also have drains in a nearby room, it is possible to connect them if they both run through the wall. Not every drain can be connected though as toilet wastewater drains shouldn’t be mixed with faucet drains in most locations. 

How to Route Plumbing Through the floor

To install vanity plumbing through the floor, you’ll first need to determine if you can access the necessary pipes and drains. Study where the drains can run. You will also have to determine the size of the drains. In most instances, this is a standard size but in some cases, you might want to increase the diameter.

After that, you’ll need to mark the lines so that you know where to make your cuts, then make the cuts so that the pipes drop into the wall cavity. You have to be careful that the tiles don’t break when you drill into them. In some situations, you will need a special drill bit to get the job done.

You also will have to study the stability of the floor joist if you want to install this on the first or second floor.

Most drains are made out of PVC. This material is glued together. You can read how to glue PVC fittings here. This is quite easy to do but can take quite some time. Make sure to clean the pipes before you do this to avoid dirt and dust inside the new drains. 

Check the slope and connections before you finish the installation of the drain. Once the drains have been glued together, it is harder to make adjustments.

You can also use PP instead of PVC. There are fittings that slide together and you don’t need to use glue to connect them. This makes it easier to make adjustments later on.

Even though plumbing through the floor has some advantages, it’s not always the best option. In some cases, you may be better off plumbing your vanity through the wall. Hopefully, after reading this article, you’re better equipped to decide which method is best for your needs. Plumbing your vanity through the wall is a great option for many homeowners