No Room For P-Trap In The Bathroom? (Here’s What To Do!)

Have you installed a new bathroom sink and vanity only to find that there is no room for the P-trap? What now? Plumbing your sink without it isn’t an option. The law requires all kitchen and bathroom fixtures to have P-traps, which are essential for preventing sewer gases from leaking into your home. There are ways you can fix things when you’re tight on space, though.

Enlarging the space under your sink when there is no room for the P-trap is easy by cutting the vanity or replacing it with a more spacious model. You could also cut the wall if the trap fits vertically but needs more horizontal space. If you can’t replace or cut the vanity, you could install a HepvO waste valve.

Why Do You Need A P-Trap?

A P-trap is a bent section of pipe that goes down and then back up before connecting to the wall drain. Due to this design, the trap looks like a P; hence, its name.

Required by plumbing codes in all states, P-traps act as a barrier between your house and the sewage system. Some of the water flowing down the drain gets trapped in the U-bend and prevents sewer gases from leaking into your home.

Are you wondering why it matters? Aside from blocking the foul smells from spreading throughout your house, P-traps also keep you safe. In fact, sewer gas contains a bunch of toxic fumes, including hydrogen sulfide, sulfur dioxide, carbon monoxide, ammonia, and methane.

An accumulation of these gases inside your house could make you ill and is potentially life-threatening.

New plumbing systems must have P-traps, according to the law. In older buildings, sinks or bathtubs may still have S-traps instead. The main problem with S-traps is the siphoning phenomenon that could suck all the water in the trap. Thus, S-traps, alongside other unsecured plumbing traps, are now banned and can’t be installed in new homes.

I Can’t Fit A P-Trap In Because It Is Blocked – What To Do?

Bathroom fixtures generally have a standard size that makes it easy to install P-traps. However, there are instances when you might have a tight space for a P-trap. The problem could be a smaller sink that is too narrow for a standard P-trap or a vanity with drawers or shelves that get in the way.

When a P-trap doesn’t fit, there is no “one-size-fits-all” fix. You must assess your situation and find the most appropriate solution. Options include using a short P-trap, cutting a slot into your vanity or wall to accommodate the pipe, or even replacing the trap with another appropriate option. Here are the most popular fixes.

Cut The Vanity/Wall

If the P-trap doesn’t fit because of the vanity or a smaller sink for space-saving, the easiest fix is to cut the vanity or wall.

Using a short P-trap could also solve the problem, but only if the space between the tailpiece and wall drain is tight. In fact, the U-bend portion of a short P-trap has the same size as a regular trap, but the horizontal piece of pipe that goes to the wall is shorter.

If you can’t find a short P-trap and need more horizontal space, you could also cut the wall and connect the trap to the drain pipe in the wall. This should give you a few extra inches of room.

How to cut the vanity?

  1. Gather the tools and materials you need, including a pencil, ruler, saw, sandpaper, and a waterproof sealant.
  2. Place the P-trap under the sink and mark the spot where you need to cut on both sides of the trap.
  3. Remove the trap and draw the rectangle that you have to cut out. This step ensures a precise cut.
  4. Remove the vanity from the wall or the vanity shelf (if possible) and cut out the marked rectangle with a saw.
  5. Smooth the edges with sandpaper and apply two coats of waterproof sealant on the edges. The sealant will prevent water from soaking into the material in case of leaks. You can now put the vanity or shelf back and install the P-trap.

Get A New Vanity

Cutting the vanity is a good solution if the trap doesn’t fit because of a shelf. However, if the vanity has a bottom drawer under that shelf, cutting it isn’t a solution. The drawer could damage the pipe when you’re opening it – unless you remove its entire back side, but that means that your items could fall and get trapped between the vanity and the wall.

When buying a new vanity, take into account the size of the trap and the length of the tailpiece. Then, make sure the vanity shelves or drawers have sufficient clearance to accommodate the fixture.

Use HepvO

If you’re having trouble fitting a P-trap in a very tight space, such as a tiny home, RV, or a small half-bathroom, replacing the trap altogether with an appropriate waste valve, such as HepvO, could be your best bet.

HepvO is an innovative self-sealing valve designed to keep fumes trapped inside the sewage system without using water. To do this, it utilizes a membrane that creates an air-tight seal under normal atmospheric conditions and opens under the water pressure of a fixture emptying.

This type of valve can adapt to all situations, allowing for a horizontal and vertical installation alike.

The HepvO waste valve is approved for use in RVs and residential applications. However, you should check with your local council or building department to ensure that you can use one in your area.


Finding out that there is no room for a P-trap in the bathroom can seem like a nightmare. However, there are several ways to fix the problem. From using a short P-trap, if possible, to making a hole in your vanity or using a waste valve instead of a trap, we hope this guide has helped you find the most suitable solution for you.

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