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

Learning how to do a bathtub replacement in an old bathroom is priceless.

Today we’re going to share tips on how to install an American Standard Americast tub. Americast is a great option if you want a cast iron tub but don't want to lug it up the steps.

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

Step 1: How to Prep the Bathtub Alcove

Old homes are never level.

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

Why?

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.

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. I helped my brother install one 4 years ago and was very impressed with the construction.

The first step is to add a 2x4 ledger board to the studs.

Screw the 2x4 to studs using 3 inch deck screws and ensure it's level.

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

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.

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.

Step 2: Installing Bathtub Plumbing

Silicone sealant should be applied to the tub drain location.

And to the bottom of the drain assembly.

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.

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.

The pipe dope helps keep a watertight seal between the ABS and drain.
Assemble the tub P-Trap. Then dry fit the 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.

Step 3: Setting the Tub

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.

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.

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.

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