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How to Replace a Bathtub: Step-by-Step Installation Guide

Dan is a licensed electrician and has been a homeowner for 40 years. He has nearly always done his own repair and improvement tasks.

Yes, you really can replace an existing tub yourself!

Yes, you really can replace an existing tub yourself!

Can I Replace My Own Bathtub?

Removing and installing a new tub can be a daunting task for most homeowners, but it is quite possible if you are willing to stretch your limits a little and spend some time doing it.

Bathtub Installation Overview

  1. Remove any wall coverings above the tub.
  2. Remove any plumbing to the tub itself; primarily the drain lines.
  3. Remove the tub.
  4. Remove any water valves and plumbing that will be replaced.
  5. Prepare walls and floor.
  6. Install the new plumbing.
  7. Install the new tub.
  8. Install any wall coverings.

A word of caution though: This is not a one-day job. The work and photos shown below took nearly a week and during that time the tub was not available for use. The bathroom toilet and sink facilities were usable but any showers had to be done in a second bath. It might be possible to limit the downtime to a single day if you plan very well and are willing to bathe in a semi-completed tub install but even that might be difficult.

The old tub, at the beginning of the project.  The glass doors have been removed and some of the wall covering.  It is still usable as a tub, if not a shower.

The old tub, at the beginning of the project. The glass doors have been removed and some of the wall covering. It is still usable as a tub, if not a shower.

1. Remove Wall Coverings

Be sure to take steps to protect your finished flooring during all work. In our case this was not necessary as the plan was to put down new flooring and the first step was to remove the existing finished floor. Laminate wood flooring is inexpensive and easy to install; if it sounds like something you would like to add to your remodel an article on how to install a hardwood floor may be of interest. It isn't necessary for a tub replacement, but will certainly add to the completed job.

The first step is to remove any sliding doors on the tub. These are common as a substitute for a shower curtain but will be in the way for any work done and must be removed before the tub can be lifted out. In this project those doors were in good condition and were to be re-installed later so considerable care was taken in removal and temporary storage. Typically, the doors will have a glide mechanism at the bottom that must be unscrewed, the doors tilted in at the bottom and lifted out of the top track, which is not connected to anything but simply lifts up once the doors are gone. Wall supports will be screwed to the wall; remove the screws and the wall tracks. The bottom track is likely held to the tub only with caulking and must be gently pried loose if it is to be saved. If not, it can be left in place for removal when the tub comes out.

In the project being described the wall area above the tub was covered in ceramic tiles that had to be removed. An attempt was made to save them, but the large majority cracked in removal and it was given up as a lost cause. Not unexpected as they were nearly 50 years old.

Any drywall or other wall covering above the tub must be removed, leaving only the studding behind them with the plumbing inside the wall. It's a good idea to turn off the water during this short phase as piping or fixtures might be cracked if considerable care is not take. You should be able to do this in a matter of a couple of hours; simply hammer a holes in the drywall and pull off pieces as they become available. Discard old drywall as it is not salvageable. Remove any nails or screws that are left behind.

At this point, a word on safety is appropriate. You are in a period when there will be nails or screws everywhere, including on scrap pieces of drywall. Don't leave them where you will step on them or otherwise be injured! We kept a small trash can to put broken drywall in and carried it out of the house for disposal every few minutes rather than let it build into a slipping or puncture hazard on the floor. There will be flying pieces and lots of dust, so both eye protection and a dust mask is a good idea. Keep your work area clean of both debris and tools.

The ceiling in this home was textured in a pattern that was not reproducible, so considerable care was taken not to damage it. A razor knife was used to cut the joint compound and joint tape at the corner of the wall and ceiling so as not to tear any ceiling sheetrock.

2. Remove Plumbing

Next on the list is removal of plumbing, particularly the drain lines connected to the tub. This can be problematic as those drain pipes can be very old and virtually cemented into place. The preferred method here is to disconnect the drain using a drain wrench such as the one pictured below. Simply insert the appropriate end into the drain and turn it with a wrench, disconnecting the tub from the drain pipe. If this works all that's left is to unscrew the overflow, but in our case turning the wrench simply destroyed the old, old tub drain, leaving everything still connected. Had the old drain not been rusted so badly it merely disintegrated this would have worked well, and it was still necessary to install the new drain.

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Using a drain wrench to unscrew the drain.

Using a drain wrench to unscrew the drain.

The next possibility is that there should be a water trap (a "U" shaped portion of the drain line) that has a large nut only hand tightened on it - loosening that nut is supposed to allow the piping to be dissembled. In this case that piping was again 50 years old and completly immovable to the point that we had to raise the tub enough to reach under with a saw and cut it off. It is also possible to open the other side of the wall from the tub to make the cut, and is preferable because during the process of lifting the tub with the drain still connected will very likely break the part of the drain that needs to remain. Another option is to go under the house (if on the first floor and if there is a crawl space rather than a slab of concrete) and cut it there. We broke the plumbing and had to replace parts later on because we did neither.

It is not a bad idea at this point to remove any other plumbing as well as the drain. Moving the existing tub may not be easy, and it is quite possible to break valving or piping. We left ours in place while being very cautious not to damage the plumbing still in the wall. If you choose this route, do make sure to turn the water off, just in case.

The old drain refused to come out.  The small cross pieces in the drain that are used to unscrew the drain simple broke free from the drain instead of turning it.

The old drain refused to come out. The small cross pieces in the drain that are used to unscrew the drain simple broke free from the drain instead of turning it.

3. Remove the Old Tub

With the drywall gone and plumbing either disconnected or removed, it's time to get the old tub out. There are three basic possibilities here, depending on what your old tub is constructed of.

  1. Cast iron: The worst scenario, but still not something that is impossible. The tub will be far too heavy to remove and carry outside the house, so the answer is to take it out in pieces. A sledgehammer will become your best friend as you literally pound it into manageable pieces.
  2. Steel: This tub is still heavy, but nothing that cannot be handled with two people. There will likely be a few nails along the top edge holding it in place. They may well be buried in caulking and require some searching, so if the tub doesn't move easily check for them. Once removed, simply drag it out of the space and carry it out for disposal.
  3. Plastic or fiberglass: The easiest of all, these tubs are quite lightweight and if it weren't for the sheer size and awkwardness they could be handled by one person. Again, remove any nails or screws along the edge, get a friend (or even your teen-aged child) to give you a hand, and work it out of the space.

Tubs are supposed to be a snug fit, and it may take a little finesse to drag them out of the typical alcove, but it's just a matter of keeping it straight and bringing both ends out at the same time. Don't let it turn, putting one end ahead of the other, but bring both ends out evenly.

With the tub removed, the overflow piping on the drain end will be exposed. If in excellent condition it could be re-used, but I strongly suggest buying a new drain kit, or "tub foot". This is the piece that goes from the overflow, connects to the drain in the tub and then to the sewer line. It contains a new drain stopper assembly and a new overflow cover that will match any new faucets or shower head you may install. They are readily available at home improvement stores in several styles and materials, but if you do order one make sure it will fit into your existing plumbing. More on that in the plumbing section.

The tub is out, with but a small section of drywall to be removed yet.

The tub is out, with but a small section of drywall to be removed yet.

4. Remove Old Water Plumbing

If it hasn't been done already, it's time to get the old water piping out of the way. Unless there is a very good reason not to, new faucets and piping should be purchased and installed, meaning that everything else be removed.

Turn off the water before proceeding! In most homes there are no water shut-off valves for the tub supply, and this means that the water will have to remain off until the plumbing work is completed. I strongly recommend that shut-off valves be installed if at all possible; supply piping was cut near the floor and valves installed there. As there would be no access after the new tub went in, an opening was cut into the opposite side of the wall, in an alcove holding the toilet, and a simple cover made for the resulting hole.

With the water off, the supply lines can be cut and valves installed. In our case this was with copper pipe; while valves can be soldered onto copper pipe a much easier solution was "push on" valves designed to simply push onto either copper, cpvc or the newer "pex" plumbing pipe. See the example below of the valve used. There was insufficient room to use a normal pipe/tubing cutter, and the use of push-on valves prohibited the rough, uneven, edge left by a saw, but a baby pipe cutter worked great. It just takes a little more time and a few more turns when using one. By installing shut-off valves you can take your time in getting new plumbing installed and tested without the necessity of shutting down all the water to the house for an extended period. The push-on valves work great, though rather expensive, and I highly recommend them for anyone not experienced in plumbing repairs. It simply pushes onto the piping without the need for any tools or sealant.

If you take this route I do suggest the purchase of a special tool to remove them, just in case. These tools are nothing but a small piece of specially formed plastic and are very inexpensive, but you will not get the valve off if you don't have one. Make sure that it is designed for the right size—our piping was all ½" and both the valve and removal tool had to be that specific size. Other fittings are available as well—we also used an elbow that pushed onto the pex pipe and was threaded on the other end for a short pipe nipple into the valve.

I had tried to remove the faucet handles before removing the tub, but even though I removed the center screw in each handle they wouldn't budge. With the tub gone and no danger of rupturing a water pipe, the solution was to take a large pair of pliers, grab the plastic handle and shake vigorously. If it had come off in pieces I wouldn't have cared, but it worked and both handles came off without further problem. That let me unscrew the large valve from the supporting wood, unscrew the shower pipe and work the assembly back through the studding it had been installed through. I saved the shower pipe for future use as I intended to use pex for new piping and preferred a solid pipe going to the showerhead for better support. The tub spout simply came out with the valve but you may or may not have some cutting or other removal to do to get the entire assembly out of the studding.

5. Prepare the Walls and Floor

Demolition is done and it's time to prepare for the new tub and plumbing!

Our floor was in poor shape as the reason for the entire project was that the piping inside the wall had been leaking for some time and had damaged both wall and floor. It is absolutely imperative that the floor be both flat and level so take some time here and get it right. We added a layer of OSB to the floor; the rest of the bathroom floor had been raised in the past and the addition under the tub would now match the rest of the floor in height. A section of older flooring, outside the tub, needed cut out and replaced because of the past leakage and we did that as well. Make sure that all the flooring is in good condition; don't fail to replace because it's "good enough". You have just one chance here!

Check the floor for level as even ¼" out of level will be visible and may affect how the tub drains. If you are installing a plastic or fiberglass tub (likely) and the floor is warped at all it will warp the tub and could crack it. That floor must be both flat and level! This is important enough that most tubs require a layer of mortar be placed down and leveled before the tub goes in. Ours did not; it was one of the reasons it was chosen over other models.

New subfloor is installed.  The opening for the drain will have to be made larger eventually, but that was easy enough with a sawzall.

New subfloor is installed. The opening for the drain will have to be made larger eventually, but that was easy enough with a sawzall.

Next are the wall studs. Most homeowners will install a tub surround rather than tile, and that means those studs not only have to be in the right place but have to be vertical and straight as well. Check each stud with a 4' level, and check as well that they are square to the floor with a large square. Check that each one is straight and doesn't warp in and out of the wall. New studs can be nailed right to the old ones to correct out of plumb studs and can be added as necessary to provide support for a tub surround.

Take care that the space for the tub isn't too large. It is generally permissible to have a one eighth inch gap between the tub flange and the wall on each end, but in our case we were well over that. We added ¼" plywood to each stud on one wall, reducing the length of the space by that amount and putting the gap well within that one eight inch.

A word on that surround and tub placement; the instructions with your surround may give stud placements, or it may not. Studs are used to glue the surround to, and thus must be in the right location to be effective, but I found that my instructions gave locations where the surround didn't even touch the wall! It projected out for a shelf, or just appearance, and the location given for the necessary gluing surface was useless. They were obviously written for a generic surround and care was not taken to be sure they actually referenced the one in the box. Make sure you understand the instructions and that they make sense!

In addition, any sliding door will require something to fasten the wall brackets to, so make sure there is something there. In our case, for instance, the surround projected out from the wall right where the door would fasten and we had to add a stud projecting out from the wall the same amount so that the finished surround would have a solid backing to screw the door frame to. Even if you don't plan a door you should probably install backing for one; you never know when you'll change your mind! This time our instructions gave measurements that were correct, but care was taken to verify that by fitting the surround wall and double checking that the added stud would actually work for the door.

With the walls and floor ready, we set the tub in for a test fit and a re-check that it didn't wobble on the floor, that the walls were plumb with it, etc. A good idea, and I recommend that step for everyone. It was easy enough to do, took only a few minutes, and could have saved a great deal of headache had we made even a small error in the floor or wall. While you're at it, measure carefully to find the center of the tub width and mark it on the wall to receive the valving or otherwise record it. You will need that measurement in the next section where you install the new faucet. Remove the tub again when finished doing this check.

Furring on the end wall to shorten the space for the tub.

Furring on the end wall to shorten the space for the tub.

6. Install New Plumbing

Before the tub can go in the new plumbing must be installed and tested. While some locations are up to the installer, code does require that the tub spout, filling the tub, have a gap of two inches above the waterline. That doesn't mean the overflow hole; it means that when the tub is filled to the point of running over the edge the spout must still have a clearance of 2". A good rule of thumb is to put the spout 4" above the edge of the tub; this meets code requirements while minimizing any possible splashing.

Here is where the measurements you took in the previous section are used. You want the valve, shower head and tub spout to all line up with the drain and overflow, which is normally centered between the two sides of the tub, and you just happen to have measured for exactly that in the last section.

Our valve instructions gave a requirement of a single pipe between the valve and the tub spout of 8 to 18" but beyond that it is up to the installer to choose a height for the valve. If a showerhead will be installed consideration should be given not to place the valve so low that one must bend over to reach it, yet not so high as to make it difficult for a child sitting in the tub to reach. There are no real restrictions on showerheads, but it is a lot easier to put one in the drywall than in the surround. In addition, I'm 6' tall and tired of bending over to rinse my hair. We put the shower head higher than normal, enough so that after the piping dips down it is still above my head. A good suggestion is to put the "drop ear elbow" (the 90º pipe elbow that the showerhead pipe screws into and has screw holes to fasten it to the wall studding) just behind the drywall. Likewise, the elbow for the tub spout needs to be behind the finished wall. Faucets will have instructions on how deep into the wall to put them as that measurement is specific to each faucet valve.

A drop ear elbow. The shower pipe screws into the upper threads while the piping to the valve goes on the lower stem. "Ears" are available to fasten to the wall.

A drop ear elbow. The shower pipe screws into the upper threads while the piping to the valve goes on the lower stem. "Ears" are available to fasten to the wall.

Valving, tub spout and shower elbow must all be fastened securely to the studding. It will most likely be necessary to add studding; in our case all three needed additional supports in the form of 2X4's placed horizontal between two studs. Take care to get them all exactly the correct distance inside the wall; in particular the valve must be very close to the distance given in your instructions.

Add whatever piping is necessary between the shut-off valves and the valve as well as between the valve and both the spout and the shower head elbow. We chose to use pex pipe and push on fittings as the quickest and easiest. Install the parts of the valve sufficient to make it usable, if not pretty. Temporarily install caps or plugs at both spout and shower locations. Turn the water on at both the new shut off valves and the faucet and check for leaks. We found a drop of water only after 30 minutes, so leave the water turned on for several hours or even overnight. As we were not in any particular hurry, we left it on for two days, checking for leaks every few hours.

7. Install the New Tub

With the plumbing thoroughly checked for leaks, it's finally time to install the new tub. The first step is to consider and plan for the bathtub "foot"—the piece that runs from the overflow outlet to the drain and onto the sewer collection. Ask yourself if that pipe can be installed and still clear any studding and the floor? Exactly how does the one you have connect and do you have all the parts?

In our case, I already knew there was a major problem in that a floor joist ran directly under the tub drain and where the connection to the house sewer should be made, and that the old sewer pipe had been installed slanted instead of straight up and down. There were two possibilities; add a new floor joist in the crawl space, spanning the same 10' that the old one did, nail it to the old one and remove a foot or so of the old joist where the tub drain needed to go. It would likely leave squeaky floors as not all the finished flooring had been removed and the subfloor could not be nailed to the new joist there but it was an option, albeit an unpleasant one.

The second option was to put in flexible pipe where necessary. A piece of slip pipe that is intended for drains and has a bellows-like arrangement that allows bending it is available.

The most common size of a tub drain is 1½", but yours could be either 2" or 1¼"; verify before buying if you will require such an adapter. I needed two; one to move the drain over about an inch before it went through the floor and one below the floor to match the angled sewer pipe, but they saved installing a new floor joist.

Loosely install the foot arrangement onto the tub and check that you know exactly how to do it and that it will clear the floor if installed before the tub is set into place. It probably won't, which means you're going to have to reach into the wall, feel under the tub and put it into place with the tub installed. You may also have to cut the floor out some to allow it to project into the floor space if the old tub was a different size than the new one. Ours was wider by about an inch, meaning that it wouldn't fit into the hole and the tub had to be slid out a bit and the hole widened.

Protect the tub with a moving blanket or another old blanket from scratches during construction. Carefully slide the tub into place and loosely fit the drain foot onto it. Don't forget to caulk between the tub and the upper piece of the drain, where it fits onto the tub! We did exactly that, even knowing better, and of course it had to be removed and caulking applied. Make sure that the caulk will contact the tub all the way around instead of fitting neatly into the hold in the bottom of the tub.

Once everything looks good, fasten the tub according to the instructions that came with it. Ours required a 3/16" hole be drilled into the tub flange and a screw put into the stud behind. Do not screw the screws in too tight; you can crack a plastic tub that way. Make sure before fastening that the maximum space between tub and stud is less that 1/8" as well and shim any gap at all before putting screws in. Tighten the fittings on the foot pipe and connect to the sewer pipe.

Turn off the water if it's still on for pressure testing and hand fit the tub spout into the pipe where it will go. After turning the water back on you can put water into the tub and test the drain pipe for leaks. Best to close the foot valve, or whatever arrangement you've chosen as a stopper to fill the tub, put several inches of water in and verify the valve works and doesn't leak the water right back out. Open the valve and again check that the drain piping isn't leaking as the large amount of water hits it all at once.

8. Install New Wall Coverings

It's the final step; finishing the walls. Most people will want a tub surround and that comes first. Fit the back piece in place, using screws just into the wood but far from tight, and check the fit of the end pieces. If they don't set vertical it's not too late to modify some of the studding so they fit properly. Glue and fasten the surround as directed, using some kind of method to apply pressure while the glue sets. We constructed a brace to go between the back wall and the sink cabinet on the other side of the room, and another to go between the two ends. Both were made with a flat piece of scrap plywood nailed to a 2X2 and covered with a towel so as not to scratch the surround and it worked very well. The surround was screwed to the wall the same way the tub was, again being careful not to over-tighten the screws.

Drywall is now added from the ceiling to the tub, leaving a gap for caulk of about ¼" between the bottom of the drywall and the surround. If you are not familiar with drywall work another article can give you specifics on how to finish drywall. Finish all joints and fill the screw dimples. At this point we chose to paint, preferring to put clear caulk over paint rather than paint the caulking.

Caulking, preferably a silicon caulk designed for tubs and surrounds, needs applied to each joint in the surround, between the tub and the surround, between the tub and wallboard and between the surround and the wallboard. We chose to put some small crown molding between the walls and ceilings rather than tape and finish the joint there as that would preserve the texturing on the ceiling.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

Questions & Answers

Question: Is there such thing as a left plumbed tub or a right plumbed tub?

Answer: Absolutely tubs are left and right plumbed. While the front of the tub has a skirt that reaches the ground, the back side against the wall does not. If you turn the tub around there will be no skirt showing; you will see under the tub.


Dan Harmon (author) from Boise, Idaho on November 08, 2018:

The handles must be taken off to affect any repairs. It is common to have a small plastic insert in the center of the handle that simply pops out with a small screwdriver or pry bar. At one time, years ago, I removed those handles and the stems, then visited a plumbing shop to find replacement ones. With the stem in hand I was able to find replacement stems and washers even though the faucet was over 40 years old. It worked for a decade or so, but eventually it was a matter of leaking around the faucet rather than through it, and a total replacement was necessary.

Good luck!

Gayle on November 07, 2018:

I have experienced a water leak in my Master Bathroom. As you wrote in your Blog, I have a Clear Plastic with a Black Circle which has a symbol of little Stars around it.

I Don't know the Company Name of this item. It also can't be plyed off like a Delta Faucet. It must be as you wrote in your Blog, you have to pull it off.

I hope this is easy. Maybe you can get me some tips on how to fix my washer faucet.

Thank you for your immediate assistance in this message.

Dan Harmon (author) from Boise, Idaho on May 13, 2018:

You know, before I started work and even during the job, it was daunting. When it was all over, looking back at it, it became "Well! That wasn't so bad after all." There was really nothing difficult, nothing terribly unusual.

Peggy Woods from Houston, Texas on May 13, 2018:

I am now convinced after reading this that I will never personally take on such a project. It is nice that you are able to do things like this for yourself. It certainly saves a lot of labor costs on the renovation budget! Enjoy your new bathtub and bathroom.

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