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Basement floor drains can be used as shower drains, but only if they lead into the sanitary drain (draining into the ground or stormwater system is against code). They will also be required to have a proper p-trap and the correct floor angle to ensure proper drainage.
So, you are installing a basement bathroom with a shower. I know how tempting that pre-existing floor drain can look. Surely, this is the simple solution to your shower plumbing!
Happily, using the existing basement floor drain could very well be the way to go. However, it might not be as easy and straightforward as you were hoping. There are several important factors to consider before taking on a project like this, so let’s go over them.
Floor Drain Must Connect to Sanitary Drain
Rainwater flows down the gutters in the street to a storm drain which ultimately leads to rivers and streams. Similarly, the floor drain in your basement was designed to carry excess water to the stormwater system from the HVAC condensate, heavy flooding, a leaky hot water tank, etc.
On the other hand, a sink, laundry, or, in your case, a shower drain must drain to the sanitary sewer or septic system as per Section P2601.2 of the International Residential Code. That way, you aren’t creating water pollution.
It’s likely that the drain in your basement connects to a storm drain or, if you have an older home, it might just drain directly into the ground by way of a French drain (a perforated pipe that allows water to filter down through a layer of gravel).
Some basement drains direct water into a tank or cistern that is emptied by a sump pump that connects to the drainage system.
So, first determine exactly what type of drainage system your basement has and where that system empties.
Generally, homes built prior to 1970 will have all the drains connected to one drain line. Modern homes will have separate drain lines for stormwater and sewage.
Homes, old and new, located in rural areas, will likely use a septic system. In comparison, homes in more urban areas will use sanitary sewers.
Is the Floor Angled Enough?
Another thing to think about is the slope of your basement floor. Is it angled enough toward the drain for your shower to drain properly?
Basement floors typically slope gently to a drain in the middle of the space. They are not designed or intended to handle the volumes of water a daily shower creates, which means that you could wind up with perpetually standing water in your shower area.
If this is just a stand-alone extra-shower-in-the-mancave kind of project, it might not be a deal-breaker for you. However, if you are making the basement area your master suite, this could present significant problems from mold and mildew to structural damage.
Does the Floor Drain Have a Trap?
Your new shower drain is going to need a trap. I’m talking about a p-trap like the one under your kitchen sink.
These are designed to keep sewer gas from coming up through the drain and stinking up the house, or, in this case, more specifically, your basement.
It is not likely that your existing basement drain has a trap installed; they are not required for stormwater systems. So, you’re going to have to take that into consideration.
Installing a trap into an existing basement floor drain means busting up concrete and possibly busting the budget as well.
Is this starting to sound like more trouble than it’s worth? Well, I’m not here to just give you problems! The next section looks at solutions to the issues of adequate floor angles and p-traps, solutions that do not involve excavations!
Solutions to Floor Angles and P-Traps
Elevated Shower Pan
An elevated shower pan may just be the answer to both the floor angle and the need for a p-trap.
They are relatively inexpensive for a standard 32”x32”x6” square pan. They can be fiberglass or acrylic and are easy enough for DIY installation.
The 6” clearance gives you enough room to install a p-trap without breaking the concrete floor, and they are designed with the ideal shower floor angle.
However, if your basement has a drop ceiling, you could be getting close to the 6’8” minimum height requirement of bathroom ceilings set by IRC. Be sure to measure carefully so that you don’t make any costly mistakes!
Upflush Drainage System
One other thing to consider may be installing an upflush drainage system.
The basic concept is an electric pump pushes the wastewater from the basement shower and sends it up to the main drain upstairs.
These units sit on top of the floor and are small enough to be concealed behind the walls of the shower. They generally only cost a couple hundred dollars and solve a lot of the challenges you’re being presented with.
Compensate for Loss of Flood Drain
One of the biggest challenges that are presented with using your existing basement floor drain for a shower is that you now have no way to drain any floodwater that may occur.
Minimize Water Entering the Basement
You can definitely reduce the likelihood of water entering the basement from outside by doing a few things around the exterior perimeter of your home.
- Ensure the backfill around the basement walls is properly graded to slope away from the house.
- Remove any foundation plantings from the basement side of the home.
- Apply waterproofing below the soil line.
- Extend or divert gutter downspouts to send rainwater further away from exterior walls.
Removing Water Without a Drain
To clear water from a flooded basement without a drain you will need to install a sump pump.
These small electric pumps can be installed right on the floor or submersible styles, such as the WAYNE CDU980E 3/4 HP (amazon link), can sit in a small pit in the floor. They work on a float system, either mechanical or sensor, whereby rising water levels turn the pump on automatically and water is pumped out to a drain or holding tank. When the water drops the pump turns off.
Dehumidifiers can be installed to cut down on condensation and the inherent dampness so common with basements.
Proper basement ventilation can also minimize dampness, although it only removes atmospheric water as opposed to standing or running water.
As always, before starting any renovation or home improvement project, check your local building codes to see what is allowable, as local codes can vary slightly from state to state.
Related article: Can You Live in a Basement Without Windows?
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