How to Installing Replacement Bathroom Tub?

An inexpensive replacement tub may be narrower than the old tub. Many people find a narrow tub uncomfortable, so buy one that's comfortable. Most tubs fit into a 60-inch opening, but some older ones may be longer. Measure to make sure your replacement tub will fit.
Some spa or whirlpool tubs fit a standard tub opening. Installing one is not much more work than installing a standard tub. A spa or whirlpool needs to plug into a GFCI (ground fault circuit interrupter) electrical receptacle.
Preparing the floor and the walls: 
If the bead of caulk at the base of a tub has even a small gap, water that puddles on the bathroom floor will seep underneath the tub, quickly damaging any bare wood. To be safe install protective flooring on the entire floor, including the area the tub will cover.
Time: 
About a day to install a replacement tub where there is an existing drainTools:   Drill, torpedo level, screwdriver, strainer wrench, putty knife, pry bar, hammer
Skills: Making drain connections in a tight spot, basic carpentry skills
Prep: Clear the area; cover the floor with plywood and a drop cloth.
Materials: Tub, waste-and-overflow unit, plumber's putty, pipe-thread tape, cement backerboard and tiles or other wall-finishing material, caulk
Step 1:Check the drain and replace any damaged parts. Consult the manufacturer's literature and measure to make sure the drain is in the correct location. Purchase a waste-and-overflow unit and determine how you will connect it to the drain line. Screw ledger boards to the studs at the height recommended by the manufacturer. Ideally the finish flooringmaterial should run under the tub.
Step 2: Working with the tub turned on its side, dry-fit the overflow tube and the shoe. Make any necessary cuts, then make permanent connections. Place the gasket on the overflow flange, position it behind the overflow hole, and insert the linkage.
Step 3:Inside the tub slip the screws into the overflow trim. Hold the overflow flange in place and hand-tighten one of the screws. Start the second screw and tighten both with a screwdriver.
Step 4:Insert the shoe tube into the opening in the overflow tube and slip the other end into the drain hole.
Step 5:Inside the tub place a rope of plumber's putty under the strainer or drainflange. Hold the shoe with one hand while you screw in the flange. Finish tightening with a strainer wrench. Clean away the squeezed-out putty with a plastic putty knife.
Step 6:Before tilting and moving the tub, plan the move so you avoid damaging the waste-and-overflow unit, which protrudes below the tub. It may work best to rest the tub on 2x4s part of the time. Move the tub into position with a helper. You may have to tilt the tub. Slide it into the opening and gently lower the tub in place. You might want a helper to guide the overflow tube into the drain line while you do this. Slide the drop cloth or any other protective material out from under the tub. Protect the tub interior.
Step 7:Check the tub for level; an out-of-level tub may not drain completely. Attach the tub to the studs according to manufacturer's directions. You probably will nail or screw through an acrylic tub flange (shown). For a metal tub, drive nails just above the flange.
Step 8:Working from behind or below, connect the waste-and-overflow tailpiece to the drain line. To test for leaks close the stopper and fill the tub. Open the stopper; watch and feel for any sign of wetness.




Step 9:To fill the gap above the tub, cut and install strips of cement backerboard, which is more moisture-resistant than green drywall. Install tiles to fit, allow the adhesive to set for a day, and apply grout. Apply silicone or tub-and-tile caulk where the tiles meet the tub.