Can The Kitchen Sink Drain Go Through The Floor?

There are very many aspects that builders and plumbers look at before deciding the best location for a kitchen sink and its drain.

Typically, the kitchen sink drain needs to be fixed in a way that it joins the main house drainage system.

Things like ventilation should also be considered when placing a drain to ensure adequate fresh air circulation.

But, Can The Kitchen Sink Drain Go Through The Floor?

Yes! A sink drain can be built to pass through the floor. The sink drain is usually passed through the nearby wall to the main drain. If you choose to pass it via the floor, you have to be more careful to lower the possibility of future drainage problems. There are reasons why you will find it necessary to pass a drain under the floor, but always ensure that there will be no licks or ventilation problems.

The process of having a sink drain pass through the floor is similar to that of passing it through the sidewall.

However, the two processes involve slightly different fittings and some added labor.

See Also: Do You Need to Earth a Kitchen Sink? 

If you are thinking of having your new sink drained through the floor, this post might be of great significance.

Installing Drain Pipes Through The Floor

A carefully laid plan is very essential when preparing to have the drainage system of your sink run through the floor.

The best plan is when you direct the drain pipes to run parallel to the floor joist. It should also get direct to the main house drainage system.

You can make holes in the floor, enabling you to lay the sink drainage through the floor joists. However, this process is labor-intensive and more expensive.

This method of installing drain pipes can also damage the structural integrity of the floor joists. In the long run, the entire floor will be damaged.

If you realize that you have no other option than running the drains through the floor, ensure you don’t interfere with the firmness and structure of the floor.

Even though running the pipes through joists is assumed to be the best way to align a drain pipe, always do it carefully to avoid causing damage to the floor structure.

Also, consider that the pipes will have more joints interconnecting the small pieces.

The pipes are usually shorter and must be firmly interconnected to prevent leakages.

Generally, the whole process of joining pipe parts is labor intensive, and your plumber might ask for more payment.

However, you have to always provide adequate material and labor so that no shoddy work is done under the floor.

Otherwise, leakages will arise if done inappropriately, which later damages the floor.

Always consider the right slope for the drainage when laying it down.

Apparently, an insufficient sloping angle will affect the flow of the dirt from the sink through the drains to the main drain tank or septic.

If you allow food debris to pass through your sink, it is important that you ensure the drain pipes are large enough, and they drain well.

Otherwise, the debris can accumulate within the pipe and eventually block it, causing significant drainage problems.

Deciding On The Best Location For The Sink Drainpipe

The location of a drainpipe from your sink is often decided on the basis of whether you are building a new house or remodeling an old home.

Basically, it is very difficult to change the existing home drainage system, which is fed by minor drains from other parts of the house.

If you choose to make a few changes, it will automatically affect the existing home structure and may even cause expensive damage to your property.

When building a new house, the kitchen sink drain is usually aligned in the wall.

This is usually because, at this initial stage, the plumber or builder is able to plan for a drainpipe that moves the floor downwards before installing the floor slab and the vertical wall.

It is naturally hard to set in a drainage pipe to a wall that is already standing. If you try, it can bring the entire wall down.

A floor drainage pipe is most suitable for a sink that is being remodeled or installed in an already-existing house.

Unless all the drainage pipes were installed during construction and they are visible, it is restricted to start digging in the wall.

Most importantly, consider having a location plan for your kitchen sink and its drainage system before starting construction or remodeling.

Consider Proper Ventilation

Ventilation is extremely important for any drainage system.

Your sink drain is not an exception in this case.

It needs to be naturally vented by incorporating it into the existing drainage system or by adding an independent vent pipe specifically designed for the sink.

When sink water flows to a sealed drain, it will obviously cause an airlock which can result in slow flow, burps, or complete no drainage in the pipes.

For new construction, the sink vent is placed on top of the sanitary  that connects the lower drain that moves to the larger drain below the floor.

This vent pipe runs upwards and is interconnected to the vertical home’s main vent.

If you are remodeling, the vent pipe must be long enough to go through the roof to the outside part.

This is basically because you cannot redirect a new vent to the original venting system. Alternatively, you can add an auto vent, which will be installed under the sink.


A sink is an essential addition to a home and can be installed when building a house or later when you get enough funds to install it.

To add on, you can choose to have a new sink to replace the old one or want to remodel your entire kitchen.

Regardless of what you are doing for your kitchen sink, the drain is the most important part to consider.

While you can pass the drain through the floor, you should be careful not to tamper with the structural integrity of your property.