Replacing an old tub faucet. Bathroom Remodel:

Replacing A Bath Tub Faucet 
Part 1 of 2
Removing The Old Faucet, Plumbing Preparations

In This Article:

We gain access behind the tub faucet, prepare the new faucet valve, cut a hole in the wall for the valve, the tub spout, and the shower pipe.

Related Articles:
Skill Level: 3-4 (Moderate +) Time Taken: 5 Hours

By , Editor


This dreary old bath tub had an ancient faucet... and NO SHOWER HEAD!

My task was to install a good tub/shower faucet and make this house a bit more livable for the next few years... until it's time to bulldoze the place and build anew.


Notice how the faucet is below the tub rim? 

That is a major code violation today.

Why? There is a rare phenomenon called back-siphoning that can occur with this arrangement.

Old tub faucet mounted to end of tub, below the rim.


In the adjacent bedroom, there was an access hatch behind the tub.

But I needed access to the entire height of the wall.


So I removed the trim around the floor and ceiling.

The baseboard was damp and beginning to rot.


I pried the paneling up with a  flat pry bar.


There was drywall underneath the paneling.


A closer look at the tub revealed a lot of rust and signs of water leakage over the years.


Some previous owner had used 3/8" copper flexible tubing to connect the water supply. This tee is a "flare fitting", which requires a special tool for flaring the ends of the tube.

I don't have tools for flare fittings, but I can easily connect to the 3/8" copper tubing by using compression fittings, which are widely available. 

The overflow tube was loose and could not be tightened. Note how the front screen holes are visible (red arrow).


Old House Weirdness:

Note in the pictures above that you can see the rounded edge of the top of the bath tub. This is an old clawfoot tub that some doofus turned into a contemporary built-in tub by building a false front and filling in around the corners. Very weird. A lot of work just to save a few bucks.


But before I could do any repairs, I needed to locate the studs in the wall (above this access hole) and remove some drywall.


I made a mark along the center of the stud, in line with the edge of the original access opening.

Then I made several cuts with a sharp knife.


And I broke away the drywall.


The existing hot and cold supply lines are barely visible here (red arrows).


Back in the bathroom...

I laid out the center lines of the faucet and the tub spout, according to the manufacturers instructions.


This is a Moen 82519 single-handle tub/shower combination faucet. This one uses threaded fittings, which are 1/2" iron pipe (IP) tapered threads.


Moen's instructions say to install this plastic plate temporarily.


Using a drill with a 1/2" chuck, and a 4-1/2" diameter hole saw, I made a hole for the faucet.

This hole could also be made with a jig saw, a reciprocating saw, or even a simple jab saw (skinny saw for drywall cutouts).


Then I drilled a smaller hole (1", I think) for the tub spout pipe.


I also drilled a hole for the shower head pipe, completely disregarding how the location blended in with existing decor.


I made a pair of adapter pipes for the hot and cold water supply lines. On the left side of each pipe is a 1/2" male pipe thread adapter. On the right end is a 3/8" compression fitting adapter.


Don't even think about trying to mate compression fittings or flare fittings to pipe threads. Iron pipe threads are tapered, so the fittings get much tighter as they are turned more. Compression threads are just regular machine screw threads (not tapered) and they rely on a brass or plastic "ferrule" to seal against a smooth seat in the fitting while squeezing tightly onto the tubing.


Continue to Part 2 of Replacing A Tub Faucet

Tools Used:

  • Heavy Duty 1/2" Drill
  • 4-1/2" Dia. Hole Saw
  • Plumbing Tools For Sweating Pipes
  • Tubing Bender
  • Tubing Cutter
  • Large Adjustable Wrenches
  • Basic Hand Tools


Materials Used:

  • Tub & Shower Faucet, Moen 82519
  • " Male Threaded Adapters
  • Adapters: " Copper Sweat to 3/8" Compression
  • " Copper Pipe and Fittings As Needed.


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Copyright 2001-2004

Written February 17, 2001
Revised December 26, 2004