How to Replace a Bathtub Drain in a Mobile Home

Bathtub Plumbing Parts & Installing Them Yourself

Plumber installing bathtub drain

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Project Overview
  • Working Time: 1 - 3 hrs
  • Total Time: 1 - 3 hrs
  • Skill Level: Advanced
  • Estimated Cost: $20 to $50

Replacing an old, leaky, or damaged bathtub drain in a mobile or manufactured home usually differs from replacing a tub drain in a typical site-built home. Mobile homes often have "garden-style" tubs with no overflow tube. The standard mobile home bathtub is called a 1 1/2 drain. It has a 2-inch hole in the tub and a 1 3/4-inch thread diameter. The drain includes a seal and nut that you tighten onto the tub.

In a standard home, the drain assembly is usually a threaded insert onto which a mounting nut is screwed from below. To fix these plumbing parts in a site-built home, you must break through the wall. A big difference when fixing the plumbing in mobile homes is you have to break through the floor; the plumbing is under the tub.

Most garden tubs have drain fittings that are removed from the top of the tub. You can get a mobile home tub drain kit with all the parts you need to replace the entire drain assembly. To replace a bathtub drain in a mobile home, secure the new drain fitting with a retaining nut on the bottom side of the tub.

Rather than call out a contractor to stop the leaking drain, here are all the steps to do a mobile home tub drain replacement yourself.

Mobile Home Bathtub Plumbing Parts and Locations

  • Water supply line: These small 3/8 to 1-inch lines, usually copper or PEX, come into the home and then branch at the water heater so some water can get heated; from there, a hot and cold line runs parallel to the faucets and tubs. These lines run under the floor.
  • Drain assembly: This is the part of the drain you see when standing inside the bathtub. It comes in different types: toe-touch, pull and turn, plug stopper, and flat top strainer.
  • Swivel connector: This is the part that the drain assembly screws into. It links your bathtub drain to your trap. The swivel nut and seal washer help provide a tight fit. It usually fits 1-1/2 inch coarse thread tub drain inserts. It uses a seal washer.
  • P-trap: This common U-curving pipe under the drain, under the floor, connects to the swivel connector, and leads to the drain line. When the water is turned off, the downward curvature of the pipe traps water at the bottom of its curve. The trapped water becomes a seal, so no gases from the drain line come backward from the sewer or septic tank to re-enter the home.
  • Drain line: The water removal system uses gravity, traps, and ventilation to move water to the sewer or septic system; it ensures that gases don't build up and re-enter the home. These lines run under the home, emptying into the waste system underground.

Before You Begin

There are two ways to remove the old drain or tub shoe. Remove it by sticking a dumbbell wrench down in the drain and ratcheting it free or loosening the nut at the bottom of the tub. Most garden tubs use a nut. After removing the drain, clean off the old plumber's putty, so your new drain can have a good seal. Teflon tape can also help seal the threads for a snug fit.

Also, if you think you have a clogged bathtub, you might not need to replace your bathtub drain. You might only need to clear the clog. Several tried-and-true methods for unclogging a bathtub include using a plunger, putting a pot of boiling water down the drain, trying a baking soda and vinegar solution, and snaking a plumber's snake or auger down the drain to clear any hair and debris out of the way.

How to Replace a Bathtub Drain in a Mobile Home

What You'll Need

Equipment / Tools

  • Tub drain wrench (also called a Dumbell wrench)
  • Mini hacksaw or hacksaw blade (if needed)
  • Flathead screwdriver
  • Plumber's tape (teflon tape)


  • New drain assembly
  • Plumber's putty
  • Additional fittings (as needed)
  • 1 1/2 inch female adapter (if needed)


  1. Remove the Original Drain Fitting

    Use a tub drain wrench to unscrew the drain fitting counterclockwise, levering the wrench against the crosshairs inside the drain fitting. If the fitting is stuck or the crosshairs break, cut the fitting with a mini hacksaw or a hacksaw blade.

    Cut through the threads and the rim of the fitting but not deep enough to go into the tub itself. Make a second cut about 1/2 inch away from the first cut.

    Pry out the cut segment with a flat screwdriver, then use the screwdriver to pry up one of the edges of the drain fitting and unscrew it counterclockwise.

  2. Prepare the New Drain Fitting

    Prepare the new drain fitting and the drain pipes for installation. Beneath the tub, locate the drain trap secured by a nut. Loosen the trap nut and move the trap and drain pipes out of the way to make room for the new tub drain.

  3. Insert the New Fitting

    Move to the top side of the tub. Roll out an even bead of the plumber’s putty and position it around the new drain fitting. Push the fitting into the drain opening in the tub.

  4. Secure the New Fitting

    Go back under the tub. Push the rubber seal, followed by the retaining nut, onto the tailpiece of the drain fitting. Screw on the nut until the fitting is tight.


    If the drain fitting spins instead of tightening, you may need a second set of hands to help hold it in place from above the tub while you tighten it from underneath. You can also use the tub drain wrench to hold the drain fitting as you tighten the retaining nut. 

  5. Install Other Drain Pieces

    Install the rest of the tub drain pieces onto the new drain fitting.

    The fittings required may vary but often include using a 1 1/2-inch female adapter that is screwed onto the drain tailpiece and using plumber's tape on the threads for a watertight seal. You may need additional pipes and fittings to complete the connection. When all pieces are in alignment, tighten the trap nut.


    Whenever possible, use trap and pipe pieces that are all the same diameter to help the tub drain faster.

  6. Check Your Work

    Have a helper fill the tub and drain it while you watch for leaks from below.

Using a Trap Adapter

An alternative method for replacing a tub drain is to use a flanged tailpiece and a 1 1/2-inch tubular trap with a trap adapter to convert back to the 1 1/2-inch drain pipe. This type of trap includes slip-joint washers that are easy to use and similar to those used on kitchen and bathroom sink drains. This alternative option makes it easy if you have trouble lining up or connecting the tub drain.

However, one potential problem with using a 1 1/2-inch tubular pipe is that the tub will not drain quite as quickly as it should. The drain also needs to be in an accessible location since these are mechanical joints that can leak more easily than glued joints. Also, if you attempt to snake the drain from the tub, the thin tubular trap can break. To prevent this, you can remove the trap from underneath the tub and snake the line from there, if necessary.

  • What is under a bathtub drain?

    The bathtub drain leads to the P-trap, a U-shaped pipe under the drain that connects to the drain line, removing water from the house.

  • What causes sewer backup in a bathtub?

    A clogged sewer line is the most common reason for sewage coming up through your bathtub. When wastewater has nowhere to go because the sewer is blocked, it will bubble up back to your house.

  • How much does it cost to replace a bathtub drain pipe?

    The average cost for a plumber to service a bathtub drain pipe is about $700. Although, depending on the severity of the problem, it can run about $225 to $1400. Since many lines run under the house, if the floor has to be pulled up, it can cost you an additional $7 to $30 per square foot to repair the flooring.