How to Add a Bathroom to a Basement the Easy Way

How to Add a Bathroom to a Basement the Easy Way

What’s the average cost of adding a bathroom to your home?

This question is a bit tricky as it will depend on what kind of remodeling you are planning. If you are trying to do work on an existing space or a simple conversion, a bathroom retouch will run anywhere from $3,000-5,000. This cost includes simple wallpaper, paint, flooring and . Installing a new addition to your home is another matter, as this will increase your price well into the $25,000-30,000 range. Keep in mind that this is generally the starting range as it can easily climb to $40-50,000 depending on the size of the room you are trying to add. The national average for a 100 square foot bathroom is around $75,000, so please keep a close eye on your budget and expenses.

Can you add a bathroom anywhere in your house?

The short answer is yes, you can install a bathroom almost anywhere that you can afford it. However, this will largely depend on your plumbing and electrical setup and what style of bathroom you want, which goes into another common question.


Steps on Toilet Installation

Here, we asked This Old House plumbing and heating expert Richard Trethewey to show how to install a toilet. The time required varies, but give yourself half a day if you’ve got a lot of experience with plumbing jobs, and a full day if you’re a novice.

2. Prep the Floor and Soil Pipe

Photo by David Carmack
  • Stuff a rag into the soil pipe to block sewer gas and prevent hardware from falling in.
  • Check that the hole in the floor is large enough to accommodate the closet flange up to its collar. If the hole needs to be enlarged, trace around the flange’s base with a pencil, then cut away the excess flooring with a jigsaw. Don’t cut any joists.
  • Dry-fit the soil pipe into the closet bend. Place the flange over the soil pipe, then measure the gap between the bottom of the flange’s collar and the finish floor.
  • Remove the soil pipe and use a handsaw to trim it to the measurement in the previous step. Remove burrs by scraping the cut edge with a utility knife.
  • Dry-fit the flange to the soil pipe, and the soil pipe to the closet bend to ensure the flange’s collar rests on the floor.

3. Install the Soil Pipe and Closet Flange

Photo by David Carmack
  • The next step to replace a toilet is to wipe PVC primer on the inside of the closet bend and on the outside of one end of the soil pipe. Apply PVC cement to those same surfaces and immediately twist the soil pipe into the closet bend.
  • Prime and apply cement to the free end of the soil pipe and the inside of the closet flange. Twist and press the flange onto the soil pipe until the collar is seated on the floor.
  • Rotate the collar until its slots are positioned to the right and left of the hole. (The closet bolts, which will be inserted into the slots, must line up parallel to the wall behind the tank.)
  • Secure the collar to the floor with stainless steel screws long enough to bite into the subfloor.

Tip: When gluing a fixed-collar PVC flange, align the bolt slots quickly before the cement sets.

4. Solder the Stop Valve

Photo by David Carmack
  • Shut off the bathroom’s water-supply valve.
  • Place a bucket beneath the supply line, then sever the line with a tubing cutter. Leave about 1 inch of pipe to attach the stop valve and escutcheon. Allow the pipe to drain.
  • Remove the valve’s handle and stem. (Heat from soldering may damage the stem’s plastic washers.)
  • Dry the pipe inside and out with a rag. Clean the inside and outside of the pipe and the inside of the valve’s inlet using a wire-brush pipe cleaner. Apply flux to both areas.
  • Slip the escutcheon over the supply line, followed by the stop valve; the valve’s outlet should point upward.
  • Heat the supply line stop valve joint with a propane torch. Once the joint is hot enough to melt the solder, remove the flame and run the solder around the joint. When a drop of solder appears at the bottom, the joint is filled.

5. Install Toilet Wax Ring, Set the Bowl

Photo by David Carmack
  • Insert the long brass closet bolts, threaded-end up, into the flange collar’s slots. Slip a brass washer over each.
  • Gently press the wax ring, flat-side down, over the flange.
  • Lift the toilet bowl over the flange, align the holes in its base with the closet bolts, and lower the base onto the ring.
  • Without twisting or rocking, press the bowl down onto the wax ring until the bowl’s base rests on the floor. If the floor is uneven, shim the bowl with stainless steel washers.
  • Slip a nylon washer over each bolt, then hand-thread the nuts. Tighten the nuts with a wrench one quarter turn at a time, alternating between the two. Stop when the wrench meets firm resistance; overtightening will crack the bowl.
  • With a hacksaw, trim the closet bolts at a point two threads above the top of the nut. Snap the plastic bolt covers into place.

*Begin with this step if replacing an existing toilet or a faulty wax seal.

6. Install the Tank

Photo by David Carmack
  • Make sure the large-diameter rubber tank-to-bowl (or spud) washer on the outside of the tank’s bottom is firmly seated.
  • Fit the small-diameter rubber tank washers into the small tank holes from the inside of the tank, then insert the tank bolts.
  • Gently lower the tank onto the back of the bowl, guiding the ends of the tank bolts into the holes.
  • Slip a nylon washer onto each bolt, then hand-thread the nuts.
  • Holding each bolt head in place with a screwdriver, hand-tighten the nuts, alternating from nut to nut and checking repeatedly to make sure the tank is level. Overtightening will crack the porcelain.
  • Connect the tank’s handle to the flapper chain.

7. Install the Supply Line and Seat Assembly

Photo by David Carmack
  • Using a tubing bender, curve the supply line to fit between the stop-valve outlet and the tank-supply fitting. Then hold the pipe, flared-end-up, between these two points and mark it half an inch below the outlet. This will leave enough line to sit inside the outlet.
  • Cut the supply line at the mark made above, using a tubing cutter.
  • Slip the plastic nut, compression nut, and compression ring (in that order) onto the supply line. Add a thin coat of Teflon paste to the valve’s outlet threads, then seat the line in the outlet, and fit the compression ring.
  • Hand-tighten the supply line’s plastic nut under the tank. Then tighten the compression nut with a wrench.

8. Finishing Touches

Photo David Carmack
  • Position the seat assembly over the bowl, then insert the plastic bolts through the seat back and the bowl’s seat holes; tighten the nuts by hand.
  • Turn on the main supply line, open the stop valve, and allow the tank to fill. Flush six times. The final step to installing a toilet is to check for leaks.

Safety Considerations

Toilets are bulky and heavy, starting around 80 pounds. Work with an assistant when moving the toilet.

If broken, toilet porcelain (vitreous china) is sharp and glasslike, so handle with caution. Take special care when tightening the bolts at the flange as this can crack the toilet base. Use an old towel to plug the open floor flange to prevent sewer gas from leaking out.


  • Putty knife
  • Bubble level
  • Adjustable wrench
  • Old towel
  • Waterproof gloves
  • Plastic bowl to catch water

Water Supply

The supply pipes for the bathroom can be copper, chlorinated polyvinyl chloride, or CPVC, or cross-linked polyethylene, better known as PEX. Polyvinyl chloride, or PVC, pipes aren’t suitable for interior residential plumbing. Each should have a diameter of 1/2 inch and connect to a main 3/4-inch pipe. It’s a mistake to draw water for any bathroom fixture from a 1/2-inch branch line that services another fixture. That creates competition for water and is one of the main reasons a shower suddenly turns cold while you’re using it. The usual practice is to “T” each supply line in at the closest available location on the main pipe. Keep the hot water branch pipes as short as possible to avoid having to wait for hot water.

Plumbing Tips for Adding a Bathroom

When you’re adding a new bathroom, consider these tips to help make your project a success:

  • Know what you want your new bathroom to look like before you start. Check out Pinterest photos and home improvement sites online for ideas.
  • Place fixtures strategically. If you can place your new fixtures close to existing water and waste lines, you can keep construction costs and plumbing bills down.
  • If you’re installing a door in your new bathroom, install one that swings out or a sliding door. This will maximize the available space for fixtures and make it easier for guests to navigate inside your new bathroom.
  • Keep an eye out for products that will make the process easier, either because they are more affordable, easy to install or both. For example, the Qwik Jon® Ultima Sewage System by Zoeller is designed so you can put a toilet just about anywhere, which is perfect for your new bathroom project. However, adding a toilet to an existing bathroom in an old house will be a huge cost saver as it will drastically cut installation time.

Basement Toilet Options

Depending on your existing plumbing, you have several choices of commodes for your new bathroom.

Pressure-assisted toilets: Although your drainage lines may technically be deep enough for gravity-fed plumbing, the fall still isn’t as strong in the basement as it is on upper floors. Instead of risking clogs with standard plumbing, choose a pressure-assisted toilet that uses air pressure to force waste through the pipes.

Upflushing toilets: An upflushing toilet is a self-contained unit that sits on the floor, so you don’t have to remove any concrete or excavate to install one. The plumbing lines run upward through the wall to the basement ceiling and connect to the sewer or septic tank line there. This is one of the simplest options for adding a bathroom to basement areas.

Some of these models include a macerating function that grinds waste down to prevent clogging. Older upflushing macerating models relied on water pressure for this grinding, which caused odor and overflow issues. New models work on electricity, which eliminates these problems. Sewage-ejector systems: Sewage-ejector tank-and-pump systems are designed to pump sewage upward to the sewer or septic tank line. They’re like small septic tanks in that they hold waste temporarily.

These come in aboveground (free-standing) and belowground versions. Aboveground models sit on the floor, so installing one requires no excavation. The toilet is positioned on top of an enclosed tank and pump unit. Your sink and bathtub or shower can also drain into this tank.

Belowground sewage-ejector systems are also available. These units involve a tank and pump that sit in a hole below your basement floor. This allows your fixtures to drain into the unit using gravity. Because they require excavation, though, they’re more work to install than aboveground models.

Composting toilets: One of the most eco-friendly solutions, composting toilets use little to no water and turn your waste into compost you can use for decorative plants. On the downside, they’re designed only for toilet waste (not sink or shower wastewater) and require good outside ventilation.

Can you install a toilet under the stairs?

Just when you thought the garage or basement was an outlandish spot for a toilet, your mind is about to be blown. Not only can you install a toilet under the stairs, but it is becoming more common every single day and it can actually increase the value of your home.

These toilets are both convenient and accessible. Like mentioned before, trying to install a toilet the old-fashioned way is going to get you into a heap of trouble, so using a macerating toilet or sewage ejector system will save you from running into any problems. For example, if you use the macerating toilet Saniflo, you don’t need access to an outflow pipe or soil stack that conventional plumbing demands, according to their website. The unit can be attached to a pipe as small as one inch because the macerating unit churns the waste from the toilet into a liquid effluent that can be easily pumped through these tiny pipes.

Think Home Climates for Bathroom Plumbing

Plumbing is an integral part of a bathroom remodels. Home Climates offers bathroom plumbing services from shower and toilet installations to leak detection and repair. You could do it yourself, but when you have access to professionals who will do the job correctly, quickly and at a reasonable price with over-the-top service, why should you? If you’re interested in making your life easier by adding a half-bath or a full bathroom to your home in Lancaster, Harrisburg, Elizabethtown, Lititz, Mount Joy or Hershey, Pennsylvania, contact Home Climates. We’ll give you guidance on all of your plumbing needs. We know plumbing disasters happen at the worst times, so remember we offer emergency service for no extra fee.


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