How to Install a Fiberglass Tub

Many bathroom remodeling projects include installing a new fiberglass tub. These are easier to install than tubs made of other materials because they are so lightweight. In most cases, fiberglass tubs cost less than other tubs of equal quality. Clean your fiberglass tub with a sponge and non-abrasive cleaner. A rag soaked with paint thinner or acetone–nail polish remover–will remove tar and many oil-based stains when scrubbed on the tub's surface. Dry a fiberglass tub after each use to keep its surface shiny.

Fiberglass tubs come in many shapes and sizes.
  1. Measure the tub and the installation area. Verify that the tub's height, width and length will fit in the area and that the tub's drain-hole placement corresponds with the drain pipe–the PVC pipe penetrating the floor near or in one wall.

  2. Connect the trip lever and waste assembly to the drain hole, found on the bottom of the tub, and the overflow hole, found on the tub's wall directly above the drain hole. A rubber gasket slips over a flange circling the assembly's waste and overflow holes. The Y-shaped assembly's bottom branch connects to the drain hole, the longer top branch connects to the overflow hole and the short male end will connect to the drain. Screw the drain hole coverplate to the waste side of the assembly through the drain hole in the tub with a screwdriver. Slide the plunger, attached to a rod that connects to the trip lever, down the overflow pipe from the inside of the tub. Screw the trip lever to the assembly from inside the tub. Keep the screws loose for future adjustment.

  3. Place the tub into the tub opening. Center the tub in its opening using a tape measure to find the center of both.

  4. Level the tub in both directions with a bubble level and shims. Rest the level on the tub's rim. If the tub is not level, the bubble will rise to the high side. Place shims under the low end of the tub until the bubble is centered.

  5. Screw the tub's lip to the wall studs with 1-inch drywall screws using a drill. The lip, the flange that extends from the tub surface along the walls, serves as a connection point. Screw one drywall screw in the center of the lip and in line with the center of each wall stud.

  6. Slide a 1 1/2 PVC brass adapter into a 1 1/2-inch PVC tail piece. Do not glue the PVC fittings and pipe until after dry fitting the entire tub hook-up. The brass adapter connects the brass trip lever and waste assembly to PVC drain pipes. A tail piece pipe has a female fitting molded into one end.

  7. Push the brass adapter onto the trip lever and waste assembly's drain leg–the pipe coming out of the bottom of the assembly.

  8. Slide the male end of the tail piece into a 1 1/2-inch PVC P-trap. Aim the P-trap's long, straight section toward the building's main drain pipe which will be protruding from the floor.

  9. Cut the P-trap's pipe three-quarters of an inch from the drain pipe and the drain pipe 1 inch from the floor with a hacksaw.

  10. Connect the two cut pipes with a 1 1/2 inch PVC 90 degree fitting.

  11. Draw check marks on the pipe and fitting connections with a pencil. The check marks at each connection must line up with each other.

  12. Disconnect each PVC connection. Clean each connection with PVC primer, both the male and female ends. The can of PVC primer will have a brush connected to the inside of the lid. Glue the fittings together, one at a time, in the order of pre-assembly using the check marks as a placement guide. Use the brush located on the cap of a can of PVC glue to spread glue on both the male and female sides of a connection. Push the connection together and twist the connection at least one-half turn.

  13. Tighten all screws holding the trip lever and waste assembly in place.