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Bathtub Replacement in Old Bathrooms: Our Step-by-Step Guide

All The Tips You Won't See in Books!!

As Seen On
by Jeff Patterson in Bathroom Plumbing, DIY Bathroom Remodel
How to Do a Bathtub Replacement Project in Old Bathrooms

Bathtub replacement in old bathrooms can be tough.

Today we share tons of great tips and prepare you for a successful bathroom remodel.

Let’s dive in and get you feeling more confident about how to replace a bathtub.

Bathtub Replacement and Subfloor Problems

Old homes are never level.

We had to level the subfloor, but only where the new tub was going.

How to level a bathtub subfloor


Leveling the entire bathroom subfloor would have created a big problem at the doorway. Steve mentions this in the video.

Had the floor been leveled there would have been over a 1 inch difference between the tile in the bathroom and the wood floor in the hallway.

Not good!

In addition, the wood in the bathroom couldn’t be removed because it was resting under the stud wall. This is the reality of remodeling older homes.

Again, Steve does an excellent job explaining the situation in the video. You might be in the same predicament!


How to Prep for an Americast Bathtub 

Installing bathtubs is different for each type of material.

Acrylic, steel, and cast iron are the three main types you’ll see in stores.

The Americast tub in today’s tutorial is made by American Standard. Americast is a special type of steel with a porcelain enamel finish.

It’s way lighter than cast iron and has a durable finish that’s more resilient to scratches than steel tubs.

You can grab an Americast tub for $325 on up.

The first step is to add a 2×4 ledger board to the studs.

How to Measure for a Tub Ledger Board

Screw the 2×4 to studs using 3 inch deck screws and ensure it’s level.

How to add a ledger board for bathtubs

Americast tubs have integral overflows which helps eliminate the chance of leaks.

Integrated Waste Overflow in Americast Tub

We chose the 60″ Princeton tub with a right hand drain orientation. You’ll see in the video that unfortunately the drain sat over the joists.

Know Drain Location

This kind of sucked. But we made it work.

After picking your tub, installing the ledger, and prepping the drain location it’s time to install the tub plumbing.


Installing Bathtub Plumbing and Making it Leakproof 

Silicone sealant should be applied to the tub drain location.

Silicone Drain Bathtub Drains

And to the bottom of the drain assembly.

Silicone Drain

We get this question a lot: why use silicone instead of plumber’s putty?

Silicone stays flexible and watertight longer than plumber’s putty.

The bottom line:

Silicone is better at preventing leaks than plumber’s putty.

Assemble the drain per the directions and apply pipe dope to the threads.

Pipe Dope Bathtub Drain

Use Channellock pliers and a tub wrench to hand tighten the drain.

Then turn the nut on the drain with the Channellock pliers 1/4 to 1 full turn.

ABS was used in this house. As such, we had to add an ABS adapter to the drain.

Tighten Bathtub Drain Nut

The pipe dope helps keep a watertight seal between the ABS and drain.

Assemble the tub P-Trap.

Tub P-Trap

Then dry fit the tub.

Dry Fit Tub

We can’t emphasize this enough:

Installing bathtub plumbing before setting it will make your life easy!!

That’s the big reason for adding the P-Trap to the tub before getting it down on the subfloor.

Pull the bathtub off the subfloor. Dry fitting cast iron tubs is a pain in the butt. As you’ll see in the video, Steve can heft the Americast tub on his own.


The Final Steps for a Bathtub Replacement Project

Americast tubs have a foam insert on the bottom.

You could set the tub on a level subfloor and be done.

But the directions say a bedding material is acceptable under the tub.

We mixed up mortar and poured it on the self-leveler.

Then a bead of silicone sealant was placed on the stringer.

Apply Silicone to Ledger

The sealant on the stringer and mortar stop the tub from creaking.

Here’s the deal:

If your bathtub installation instructions call for mortar…USE IT.

We’ve heard too many stories of people tearing out new bathtubs after a few years because of leaks. Mortar helps prevent this from happening. Acrylic tubs are particularly prone to cracks if installed without mortar.

Guess how much a 50lb of mortar costs?

$5 to $15

Whereas a new tub costs way, WAY more.

We set the tub in mortar and double checked that it was level.

Level Bathtub

Finally, the tub was attached to the studs using galvanized screws and washers.

Watch our video for more tips and to see how Steve installed this tub in less than an hour.


What’s Next

Our next tutorial shares how we installed the mixing valve in this shower. There are tons of tips for beginners.

If you’re doing a bathroom remodel and want to simplify the process enroll into the Bathroom Repair Tutor Video Library

We show how to build showers (Schluter, Wedi, Curbless, etc.), install tile, upgrade basement bathrooms, and more.

The extra guidance is invaluable

Enroll Today



Jeff Patterson





  1. Nate Ensor says:

    What a conveniently timed post! Getting ready to do do exactly this in our never before renovated bathroom tub from 1947. I just recently heard about Amercast and was looking around for some info. So I don’t know much about it. As to the tool, I’ll need something better than my old non-impact cordless with the old style bulky batteries especially since my beloved corded finally died after mixing cement! Thanks for the info.

    1. Awesome Nate, glad this tutorial helped. Bathtub replacement projects are a great way to save a ton of money on a bathroom remodel. You likely have a cast iron tub. I recommend using a sledge hammer to break it up into pieces. It will be way easier to remove that way. Just be sure to turn off the water and remove the waste pipes before breaking the tub. Btw, I think my corded hammer drill is going to bite the dust like your drill. It’s starting to smoke while mixing up mortar and other stuff, LOL.

  2. Michael Ruf says:

    Looks a bit more extensive than when I replaced a tub 20 years ago. Due to a prior water leak, I was also required to replace the subfloor. Having the proper tools is critical. I did not but made do.

    1. Jeff says:

      Yah Mike, this old house had a lot of wonky things. That Bathtub installation could have been a challenge if the self-leveler wasn’t used. Steve and I wanted to share the tips from this Bathtub replacing so that folks would be more comfortable with untraditional situations. Older homes are great but can be a pain in the butt to remodel.

  3. Tim Harrison says:

    Keep them coming! Your tips are great resources for double checking steps for pro’s and novices alike. Thanks for your help.

    1. Jeff says:

      Thanks Tim, we liked making this Bathtub replacement tutorial because it wasn’t straight forward. Most of the houses we work on are older and represent what a lot of folks deal with when Remodeling.

  4. Roy Beman says:

    Great post, I have done several tub projects, and the greatest fear is to overlook something which will “bite your butt” later. The more
    information one has prior to taking action, the less chance for unwanted events to occur. I appreciate the opportunity to win a tool which I cannot afford to buy, since I am retired and on a fixed and shrinking income. I love your posts, keep up the excellent work.

    1. Jeff says:

      Thanks Roy and you’re right – these Bathtub Remodeling projects can bite ones butt if not planned out properly. We enjoy sharing the tips so that others have an easier tips installing bathtubs.

  5. Brandon Jones says:

    I’ve been considering replacing the tub in my master for a while now. This tutorial makes it look straightforward enough that I might actually take the plunge.

    1. Jeff says:

      Awesome, let us know if you have any questions about replacing a Bathtub. There are a lot of options but we like the Americast tub and a few other acrylic options. Cast iron is great but super painful to install by yourself. Installing bathtubs isn’t so bad if you have a plan. The other thing to consider is how to waterproof the walls. We have several tutorials on that.

  6. Danny says:

    Another awesome tutorial guys! I had put my bathroom reno on a brief hold due to other plumbing issues in the home. I’m almost done with that now and moving back to the bathroom soon. Needless to say the right tool always makes the job easier. I put a lot of wear on my driver the last few weeks and noticed it smoking, hopefully it was just a one time thing.

    1. Jeff says:

      Glad you liked this tutorial Danny. I’ve had the same thing happen with my hammer drill – started to smoke the last few times while mixing thin-set. Let us know if you have any questions about a bathtub installation. We’d be happy to help. We also have a tutorial on how to install an acrylic tub if you go that route. This Americast tub is pretty awesome though, the finish is sturdy and better than those cheap steel bathtubs for only a few hundred bucks.

  7. Andree Kehn says:

    We recently bought a 100 year old house in massive disrepair. We have demoed it down to the studs. Needless to say, the sub floor is rotted and getting the plumbing installed is one of the first things on our list. I am intrigued about this idea of leveling only the floor under the bathtub. Excited to get going, although very very apprehensive. Ha! Thanks for the matter of fact approach and step by step directions. Will go check out these steel tubs. I assume they hold heat better than plastic. I am slowly letting go of my cast iron tub dream.

    1. Jeff says:

      Cast iron bathtubs are definitely sturdy but not the easiest to install. I’m not sure about Americast tubs holding the heat longer than acrylic tubs but it would make sense. I can tell you that having the floor level and the mortar under the tub make a big difference. Installing bathtub plumbing can always be tricky. One thing to remember is stick with ABS if you have ABS, same thing with PVC. It’s best not to mix the plumbing if you can. Although they do make glue for ABS to PVC connections but it might not be approved in all towns. If you have any questions when you do your remodel just let us know. We’d be happy to help.

      1. Andree says:

        Thanks Jeff!

  8. Antonio Prioleau says:

    Great post and video! I’m planning on renovating our master bath next year. I’m not a fan of the standard fiberglass tub/shower alcoves in our 3 yr old home we just purchased a few months ago. Before any problems occur I’d rather replace the bath tub with a tile surround and new floor tiling. That tub is pretty impressive with the integrated overflow design. Having an impact drill is definitely handy and makes any job quicker. Milwaukee is a great brand by the way! Keep up the great tips!

    1. Jeff says:

      Totally agree, those fiberglass surrounds aren’t pretty. They do serve a purpose for folks on a budget. But these days tile and grout can be very easy to maintain. If you’re replacing a bathtub and want it to have tile I like large formats, e.g. 12×24, with small grout lines. That way you won’t have a ton of cleaning. Urethane and epoxy grouts can also be very helpful. Let us know if you have any questions when you start your bathtub project.

  9. Jim B says:

    It’s a great feeling after you remove an old HEAVY cast iron tub with an updated model!! Great project advice!!

    1. Jeff says:

      It sure is a great feeling to remove and replace a cast iron tub. Those bad boys are heavy. Even a small piece can weight 10 to 20 lbs. Amazing how sturdy those old tubs were back in the day…and still are. But technology for bathtubs has come a long way. Americast is part of that and it’s way lighter than cast iron.

  10. Mongo Bailey says:

    It’s nice to know that real remodeling has various challenges. It’s definitely not like the TV shows that make it look like there are never any issues and everything is perfect.

    1. Jeff says:

      TV shows drive us bonkers. One minute they have a problem and go to commercial break. When they come back it’s like the issue was no big deal. If only real life were that simple, LOL. Bathtub installation has gotten easier because of the new materials. And we wanted to share an uncommon situation – or common, depending on your home. Thanks for the kind words.

  11. Dave Louw says:

    I want to replace my tub because I’m still mad at myself for using the construction adhesive option rather than the mortar bed. Creak. Creak. Creak. 🙁

    I’ve been eyeing that Surge driver for a while now but I bought the regular Milwaukee impact driver just before it came out. So I’ve had a hard time justifying replacing a perfectly good tool in my lineup.

    1. Jeff says:

      Ah man, that’s a bummer. Yah, mortar is the best when replacing a bathtub with a new one. Lesson learned. If you decide to tear out your bathtub and replace it let us know if you have any questions.

      Milwaukee does make great tools. The normal impact driver has plenty of power. I like the Milwaukee SURGE because it’s quieter. Been using it for several months and have no complaints. Too bad that don’t have a trade-in deal. That would be cool, to trade in old tools for newer ones. Hmm, wonder if they have something likes this and we’re not aware of it.

  12. Keith Morreale says:

    Thanks for another great post. I’m a first time home owner and you-tubing DIY builder and your tips and tricks have made my bathroom renovation a lot easier and my only gripe is I wish I had found it sooner. Ive actually had to tear out parts of the bathroom after going over your information because I realized I had done some things completely wrong. I’m renovating an early 50’s model bathroom now. I tore out the 7 yes SEVEN layers of flooring material and the 1/2 plywood subfloor in order to sister every joist before going with 3/4″ subfloor, self leveling underlayment and 1/4 ceramic tile. Have an open walk in shower with 16″ ceiling mount rainfall shower head, shower tile floor that is flush with the connected sunken tub. It’s been an interesting experience so far and thanks to your info and videos It’s coming along pretty well. If this old Army Grunt can figure this out, anyone can. Thanks again. and keep it up. RLTW

    1. Jeff says:

      Hey Keith, thank you for serving our country – you’re right RLTW.

      Man, your bathroom remodel sounds fantastic. Great job just demoing the space let alone assembling everything. Send me some pictures if you have time. We’d love to check them out.

  13. sean luk says:

    My bathtub needs replacement after quite a number of years of wear and tear one of the recommended choice after much research on quality and performance is Americast an exclusive, patented material used in American Standard bathtubs. American Standard’s unique patented process that fully bonds a high quality porcelain surface with an enameling grade steel and a molded reinforcement composite backing, the best in its strength by design and excellent quality.
    I’m currently doing a bathroom remodel and I need all the tools as much as possible to get my DIY project up and running.

    With the Milwaukee’s new SURGE impact driver with its excellent quality can certainly stand up to the toughest challenge in any job, as a DIY person I can recommend Milwaukee as a selected choice where I ‘m the owner of quite a few of Milwaukee’s Power tools with its performance and durability said it all.

    1. Jeff says:

      If you decide to replace your tub this is a great option. Setting the tub in mortar is our biggest tip. Installing Bathtub plumbing and setting the backer board have their own challenges. If you have any questions just let us know.

  14. Robert Febo says:

    I did the bathroom upstairs and used your previous guide and it was tremendously helpful. I did not remove the tube but removed all the walls. Used cementous boards and new tiles, installed a new toilet, exhoust fan, lighting and sink. When i get to do our bathroom I will definetly look up your site again. I even bougth a wet table saw from LOWES. The saw work great. I was able to cut perfect 45 degree angle cuts and cut to the correct lenght so all the chair rail peices align with the tiles.

  15. William King says:

    I’m looking at an Americast soaker tub. The higher height (17 inches) will allow me, at a larger girth, to fully soak in a tub without having an Archimedes moment followed by a tidal wave. My tub will be situated very much like the video and being an Americast tub rather than cast iron I’ll be able to horse it into place without suffering a permanent injury to my manhood.

    Having the right tools when and where you need them just makes the job go that much smoother. Not having to yell “Honey, can you run out and get the Milwaukee Impact Driver, I’m stuck between the way and the tub?” is the icing on the married renovation cake. Thanks for the great videos.

    1. Jeff says:

      LOL, you’re too funny many. I love it.

      Those larger tubs are nice. Anyone who likes taking baths needs a soaker tub.

  16. Vallaree Spires says:

    I bought a foreclosure that was built in 1979, and the place needs a full remodel, however I have to work within a budget that doesn’t give me room for a pro to do the work! The bathtub has developed a leak, so this video and walk through couldn’t have come at a better time! The Americast product looks beautiful, and easier for me to work with by myself. Thanks so much for all the great tips and tricks you give every week.

  17. Josh Marrah says:

    Thanks so much for putting all of these up. I have learned a ton and am in the middle of rehabbing two kitchens and baths in a 2-flat. This has been a great resource. Looking forward to installing the tub and closing up the walls!

    1. Jeff says:

      Wow, you’re in the middle of it!! Glad the tips are a help. Take lots of pictures. We’d love to see your progress. Let us know if you have any questions.

  18. Roger says:

    A bathroom remodel is on the schedule for this winter. That tool would be handy because I’m sure I’m going to have to repair the sub-flooring. Great videos.

  19. Edward Balek says:

    We’re putting together plans to gut our second full bath. The impact driver would certainly help.. Following your posts helps a great deal.

    1. Jeff says:

      Looking forward to lending a hand, we have a ton of great tutorials that will help. If you have any questions feel free to post them on the site or email me directly.

  20. Ben West says:

    Finally getting ready to do a shower remodel after two years of procrastination. Going to register for courses soon to get ready!

    1. Jeff says:

      Thanks Ben, let me know when you register and we’ll be there to help you get started. You’ll like all the videos and the support. Basically Steve and I answer all the questions. Materials are constantly changing and we plan on adding tons of new videos to Bathroom Repair Tutor. I was just filming one today and next week we’re filming an entire walk-in shower installation, including the tile work.

  21. Beth C Kingsborough says:

    I seriously can’t wait to start on my bathroom. It’s a NIGHTMARE! I’m only 32 and just learning how to do all this home improvement stuff because I’ve had cancer for, oh ya know, a decade. Water under the bridge! I put an IKEA cabinet together the other day! I also hung curtains (a daddy visit was required)! I’ve never even hung pictures around here…it didn’t seem relevant. At any rate, my bathroom is in my crosshairs! 🙂 Haha.

  22. Danny Greene says:

    Not a job that I am looking forward to doing , but my mom’s house built in the earlie 1960’s needs a complete bath make over. This does give some great guidance on how to do the job.

  23. Kurt says:

    Replaced a tub has always been intimidating to me too but with these tips and the right tools I think I can do it.

  24. Dan Hignight says:

    Hey Jeff. Great tips on the bathtub. Preparing to replace a tub in a 1961 home. Floor definitely not level. Thanks for the advice!!!

  25. Debbie Wilhelm Sims says:

    My tub needs to be replaced because the plumbing is leaking and the tub is in bad shape and very old and the floor around the tub needs work from the leaking. I have watched many of the remodeling videos and find them very helpful and easy to follow. I got my husband to watch several to help him through a few projects. The impact tool would make world of difference for me and make repairs so much easier. Thanks for the great videos that makes a women home repairs easy!

  26. John Mitch says:

    Great post, as usual. And timely as well. We’ve selected the American Standard Princeton tub for our bathroom remodel. I wasn’t planning on setting it in a bed of mortar though. Glad I happened upon this article/video.

    1. John Mitch says:

      Oh, I didn’t mention why I would want this impact driver. I am planning on using cement board for the underlayment and I think this tool would make drilling the screws through it a breeze. Besides, you never can have too many tools 🙂

  27. Squafdonoboles says:

    How do you install the trap after the tub is already in place?

  28. Bristol Builders Network says:

    Excellent advice and a thorough tutorial. Here at Bristol Builders Network we always recommend to our clients that they use the services of a professional bathroom fitter. As I doubt many of them would be up to the job themselves

  29. Dave Louw says:

    Hi Jeff,
    Did the results of the giveaway get announced and I missed it somewhere?

  30. Thinho says:

    Hello J.
    May I ask you something?
    If the floor is damaged after I remove the tub, do I have to cut out the damaged floor ( around the tub) and replace it, or can I just put it (1/4″) on top and overlap the damage one?
    I love all your video it helps me a lot ……………….awesome 👍

  31. Brittany says:

    We’re remodeling our bathroom and wanted to use the same fiberglass tub that was in the space. The people before us used MDF for the subfloor so pulled tub out to replace floor and use mortar. One of the thin pieces of the tub underneath broke off while taking it out. Is the tub still salvageable with the mortar to support it?

  32. Jim Curtis says:

    Everything looks good except plumbers putty should be used on the tub side of the strainer instead of silicone and pipe dope not necessary on bottom threads. Serves no purpose

  33. Spa Pools Taupo says:

    Hi, thank you for such a brilliant post. I have been reading some blogs that gives me more knowledge about bathtub replacement. I must say this is one of the best among them. You have done a great research for I feel, thanks for sharing.If you are looking same kind of valuable information, then can also visit

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