How to Install a Bathtub

Installing a bathtub is not a job to be undertaken lightly. If you're considering replacing an existing tub, be sure you have checked out your other options, such as reglazing or adding a new bathtub liner. Both of these options make use of the existing walls and plumbing, and they don't require that you physically remove the old tub. However, if you have already removed the old tub or are putting the bathtub into new construction (where you have access to the plumbing and the walls aren't finished) the job becomes more manageable. Even so, installing a bathtub requires advanced plumbing and construction skills as well as some heavy lifting.

  1. Gather together your materials. See "Things You'll Need" below.

  2. Frame the walls so that the bathtub just fits into the alcove, leaving a gap of 1/8 inch around the edge.

  3. Install the rough-in plumbing supply lines for the faucet, risers and showerhead.

  4. Slide the tub into place and check for level. Use plastic shims to level the tub (wooden ones are more likely to rot over time). After the tub is level, mark the top of the tub's nailing flange on the studs.

  5. Determine the positioning of the ledger boards. These boards will attach directly to the wall studs underneath the lip of the tub and help to support it.

  6. Install the P-trap and drainpipe so that the top of the P-trap is level with the floor and will be centered underneath the drainpipe from the tub.

  7. Assemble the drain pipe and overflow pipes and dry fit them to the tub so you can measure the required length to attach the drainpipe to the P-trap. After measuring, cut them to fit and attach them to the tub.

  8. Install the ledger boards on the previously determined markings. Use galvanized nails or screws to prevent any rusting.

  9. Slide the tub into place and set it on the ledgers. The drainpipe from the tub should slide into the P-trap.

  10. Fasten the tub in position by nailing through the flanges. Here again use galvanized nails.

  11. Insert the drain plug assembly through the overflow opening, then attach the cover plate for the overflow.

  12. Turn on the water and test your plumbing and drainage systems for leaks.

  13. Have your installation inspected.

  14. Finish the walls and install the showerhead, faucet handles and tub spout.


  • In many jurisdictions plumbing installations need to be inspected prior to use. Check your local building codes and, if necessary, get yours inspected. If you don't, you could be forced to remove it.