how to install a bathtub

Replacing a bathtub or installing a new one is a difficult work that requires some technics and tricks.

But, if you have some plumbing experience, you can deem it as a DIY project that you feel comfortable tackling. because Installing a bathtub is a complex job that shouldn’t be attempted by novices.

I’m here for thais reason, so, keep reading and focus in order to claim the fruits of my experience in this field of work.


Most homes are equipped with a bathtub that includes a tub surround and shower. By combining the tub and the shower in one fixture, you conserve precious bathroom floor space and simplify the initial installation. Plus, you only have one bathing fixture that needs cleaning.

But because tub-showers are so efficient, they do get a lot of use and tend to have fairly limited lifespans. The fact that the most inexpensive tubs on the market are designed for alcove use also reduces the average lifespan.

Pressed-steel tubs have enamel finishes that crack and craze; plastic and fiberglass tubs get grimy and stained; and even acrylic and composite tubs show wear eventually (and as with other fixtures, styles and colors change too).

The plumbing for a bathtub includes hot and cold supply pipes, shutoff valves, a faucet, and a spout. Supply connections can be made before or after the tub is installed.
The drain-waste-overflow system for a bathtub includes the overflow pipe, drain T-fitting, P-trap, and branch drain. The overflow pipe assembly is attached to the tub before installation.

Plumbing an alcove tub is a relatively difficult job because getting access to the drain lines attached to the tub and into the floor is often very awkward.

Although an access panel is required by most codes, the truth is that many tubs were installed without them or with panels that are too small or hard to reach to be of much use.

A drain-waste-overflow kit with a stopper mechanism must be attached to the tub before it is installed. Available in both brass and plastic types, most kits include an overflow cover-plate, a height-adjustable overflow pipe, a drain T-fitting and tailpiece, a waste drain tube, and a drain cover-plate that screws into the drain tube.

If you are contemplating replacing your tub, the first step in the decision process should be to find the access panel and determine if it is sufficient. If it is not (or there is no panel at all), consider how you might enlarge it.

Often, this means cutting a hole in the wall on the adjoining room and also in the ceiling below.

This creates more work, of course, but compared to the damage caused by a leaky drain from a subpar installation, making an access opening is a little inconvenience.

Add fiberglass insulation around the body of a steel bathtub to reduce noise and conserve heat. Before setting the tub in position, wrap unfaced batting around the tub and secure it with string or twine. For showers, deck-mounted whirlpools, and saunas, insulate between the framing members.

Before You Start

Tools & Materials

  • Channel-type pliers
  • Hacksaw
  • Carpenter’s level
  • Pencil
  • Tape measure
  • Saw
  • Screwdriver
  • Drill
  • Adjustable wrench
  • Trowel
  • Shims
  • Galvanized deck screws
  • Drain-waste-overflow kit
  • 1 × 3, 1 × 4, and 2 × 4 lumber
  • Galvanized roofing nails
  • Galvanized roof flashing
  • Thinset mortar
  • Tub and tile caulk
  • Propane torch
  • Eye and ear protection
  • Work gloves

Shut off the water at the mainline. The first step is to turn off the water for the bathroom you’ll be working in. Locate the line and shut it all the way off. Then, open the faucet in your tub to drain the lines.

How to Install a New Bathtub (alcove Tub)

1. Prepare for the new tub. Inspect and remove old or deteriorated wall surfaces or framing members in the tub area.

With today’s mold-resistant wallboard products, it makes extra sense to go ahead and strip off the old alcove wall coverings and ceiling down to the studs so you can replace them. This also allows you to inspect for hidden damage in the wall and ceiling cavities.

2. Check the subfloor for level—if it is not level, use pour-on floor leveler compound to correct it (ask at your local home center).

Make sure the supply and drain pipes and the shutoff valves are in good repair and correct any problems you encounter. If you have no bath fan in the alcove, now is the perfect time to add one.

3. Check the height of the cross braces for the faucet body and the showerhead. If your family members needed to stoop to use the old shower, consider raising the brace for the showerhead.

Read the instructions for your new faucet/diverter and check to see that the brace for the faucet body will conform to the requirements (this includes the distance from the surrounding wall as well as height). Adjust the brace locations as needed.

4. Begin by installing the new water-supply plumbing. Measure to determine the required height of your shower-riser tube and cut it to length.

Attach the bottom of the riser to the faucet body and the top to the shower elbow.

5. Attach the faucet body to the cross-brace with pipe-hanger straps. Then, attach supply tubing from the stop valves to the faucet body, making sure to attach the hot water to the left port and cold to the right port.

Also, secure the shower elbow to its cross-brace with a pipe strap. Do not attach the shower arm yet.

6. Slide the bathtub into the alcove. Make sure the tub is flat on the floor and pressed flush against the back wall.

If your tub did not come with a tub protector, cut a piece of cardboard to line the tub bottom, and tape pieces of cardboard around the rim to protect the finish from damage.

7. Mark locations for ledger boards. To do this, trace the height of the top of the tub’s nailing flange onto the wall studs in the alcove. Then remove the tub and measure the height of the nailing flange.

Measure down this same amount from your flange lines and mark new ledger-board locations.

8. Install 1 × 4 ledger boards. Drive two or three 3″ galvanized deck screws through the ledger board at each stud.

All three walls should receive a ledger. Leave an open space in the wet wall to allow clearance for the drain-waste-overflow (DWO) kit.

9. Install the drain-waste-overflow (DWO) pipes before you install the tub. Make sure to get a good seal on the slip nuts at the pipe joints.

Follow the manufacturer’s instructions to make sure the pop-up drain linkage is connected properly. Make sure rubber gaskets are positioned correctly at the openings on the outside of the tub.

10. Thread the male-threaded drain strainer into the female-threaded drain-waste elbow. Wrap a coil of plumber’s putty around the drain outlet underneath the plug rim first. Hand-tighten only.

11. Attach the overflow cover plate, making sure the pop-up drain controls are in the correct position.

Tighten the mounting screws that connect to the mounting plate to sandwich the rubber gasket snugly between the overflow pipe flange and the tub wall.

Then, finish tightening the drain strainer against the waste elbow by inserting the handle of a pair of pliers into the strainer body and turning

12. Place the tub back into the alcove, taking care not to bump the DWO assembly and disturb the connections.

You definitely will want a helper for this job. If the drain outlet of the DWO assembly is not directly over the drainpipe when the tub is in position, you’ll need to remove it and adjust the drain line location.

13. Attach the drain outlet from the DWO assembly to the drain P-trap. If your alcove walls are covered, you will appreciate that you spent the time to create a roomy access panel for the tub plumbing.

Test the drain and overflow to make sure they don’t leak. Also test the water-supply plumbing, temporarily attaching the handles, spout, and shower arm so you can operate the faucet and the diverter.

A tub alcove is sized to accept a standard bathtub, usually 5′ long in most of North America. A tub with an apron is typical, but you can build out the front instead if you choose.

14. Drive a 1½” galvanized roofing nail at each stud location, just over the top of the tub’s nailing flange (inset).

The nail head should pin the flange to the stud. For extra protection against moisture penetration, nail strips of metal flashing to the studs so they cover the tub flange.

15. Install the wall coverings and tub surround (see pages 110 to 113 for a 3-piece surround installation). You can also make a custom surround from tileboard or cement board and tile.

16. Install fittings. First, thread the shower arm into the shower elbow and attach the spout nipple to the valve assembly.

Also attach the showerhead and escutcheon, the faucet handle/ diverter with escutcheon, and the tub spout. Use thread lubricant on all parts.


Recent Content