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Replacing old tub with shower only

My wife and I are buying a home built in the mid 70's that has bathtubs only.  I plan on doing the remodel myself but have never done much plumbing and what I have done was many years ago.  I would also note that the house is in the country and we are not required to have any permits or such.  I'm ripping out the old tub and plan on installing a tiled shower but need good instructions on plumbing for the new shower and recommendations on what I should do about the drain for the new tiled shower. (floor is concrete slab)

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Posted 2012-02-19T16:00:53+0000  by DIYba12 DIYba12

Hello DIYba12,


 Welcome to the community and congrats on your new home purchase.


Let's get you started.


Obviously, once the tubs are ripped out your fist step is going to be changing the location of the existing drain outlet. To ensure proper drainage and proper slope of the floor new shower drain needs to be centrally located.


Having said this is a home built on slab in mid 70’s cast iron pipe is to be expected – be prepared and make sure you have tools and materials needed to work with this type of pipe. Jackhammer and sawzall with bi metal blade are must haves for this type of project.



When making an opening in the concrete slab for the new P trap, position the opening strategically around the new connection point’s .See attached drawing.



Goal is to minimize unnecessary concrete work-keep in mind any concrete removed needs to be filled back before new shower can go in place.


Also if this is the one way drain (nothing past the tub) you can leave the old pipe and P trap in the concrete.


Be careful and watch for the water lines. It is not uncommon with on slab homes to have underground water lines. These lines are typically placed along the drain pipes; they are type K copper and are real bear to repair. What else…


Cast iron.


Cast iron is still required by code for most underground sewer installations. Regardless of the requirements and need for permits you should continue this good practice and make your new connections with cast iron.

Transitioning from cast to PVC it’s almost always prone to leaks. And this is not a place where you want to have leaks. You need a P trap – don’t try to make turns with regular 90 elbow, you need a p trap to prevent gasses from backing up. Just in case this is how P trap looks like;

P trap.jpgNo hub P trap.jpg



New connections.


Your new connection from the existing pipe to the new fitting (P-trap) is going to be hub free.

Couplings used for this type of connection need to be rated for underground repair applications. These are called strong back no hub couplings. See attached PDF;


 strong back.JPG

And I think that’s It, I got it all covered.


If you any additional questions please feel free to post back – we are here to help.



Posted 2012-02-20T17:39:26+0000  by George_HD_CHI

Thanks for all of the great info!  Now for another wild question...My wife now has an idea of completely re-arranging the bathroom layout which would mean moving the toilet and shower.  Would this be wise...possible...difficult?????

Posted 2012-02-23T01:04:48+0000  by DIYba12

Hello DIYba12.


My first thought in reading your question was that pre-made shower bases are available to directly replace a bath tub.


Stores, (and, stock models which have the drain at the end at the same location as the tub drain.


E.L. Mustee Base.jpg

Online at you can find many more options, like this:

Kohler Shower Base.jpg

The obvious benefit here is that you would avoid a lot of the concrete work and the risk of hitting water lines.  If you want a tile base though, then you have some digging to do.


Moving the toilet and shower to different parts of the room will require a lot of concrete demo and repair.

Is this wise...possible?

That's up to what you want.  A plumber would do this for you no problem, so it's certainly possible.

Difficult?  Well, busting up concrete slabs is fairly simple but not easy work.  The same goes for pouring the slab repair concrete.


Anyway, I just thought I would give you another option.  You can still tile the shower surround if you want.


If you want a tile shower base, ChrisFixit has done an excellent series of posts on "Steps for construction of a shower pan from scratch".

Shower base for Tile.jpg

Once you have the walls framed and a base in, it's time to set up the walls.  BlakeTheDiyGuy has done a superb video in his post "Shower Repair/Replace".

Tile shower walls.PNG


I hope this helps,



Posted 2012-02-24T17:18:45+0000  by Chris_HD_CHI



My boyfriend and I just recently bought a 70s home as well and I am thinking of updating our only bathroom in the house. I am planning on sticking with the current floor plan. The things I would do are to replace the sink with a pedestal sink and  taking out my current tub and replacing it with a shower only. So, I figured I won't really need to do much plumbing. Is this assumption right? Also, I read your suggestion about replacing the tub with a pre-made shower base. How long would it take to finish if we opt to install the pre-made base instead of tiling the floor?


Thank you,



Posted 2013-06-28T20:04:32+0000  by tamalc
Hi Tamara,

Replacing the tub with a shower pan wouldn't be too difficult as long as the existing drain matches the required location for the new shower pan.

Once the shower pan is attached to the drain, tiling the shower surround is almost like any other tile job ... except you'll use waterproof WonderBoard as your backing.

You can add two coats of RedGard Waterproof and Crack Prevention Membrane to ensure the joints in you backing are water tight.

The apply your mastic and set your tile.

Your Flooring Associate can help you select these products.

Personally, I like the ease of installation of a shower pan.

In a custom home you'll more likely find a tile shower floor.
Posted 2015-11-05T22:35:32+0000  by Pat_HD_ATL
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