How to Cap an Old Shower Drain

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Things You'll Need

  • Tape measure

  • Drain pipe cap

  • Pipe cleaner/primer

  • Pipe cement

  • Ratchet torque wrench

  • Emery cloth

  • Wire brush

  • Flux

  • Acid brush

  • Solder

  • Propane torch

  • Sheet metal

  • Cloth or rag

With the shower gone, a drain pipe remains to be capped.
Image Credit: Jupiterimages/ Images

It's startling how taking out an old shower inside your bathroom will change the atmosphere in your bathroom. Redesigning it with a new shower enclosure allows you the opportunity to start over again. Or perhaps you prefer eliminating the shower entirely, giving your bathroom the feeling of luxurious spaciousness. But taking out the shower itself isn't enough. Unless you plan to attach a new shower to the old shower drain pipe, you're going to have to cap it. Capping off a drain pipe prevents sewer gasses from rising into your home and allows you to finish the floor over it.

Step 1

Measure the diameter of the drain pipe -- the distance across the center of the pipe -- hooking the tape measure over the pipe wall on one side and measuring across. Also note the pipe material. Drain pipes are usually from 1 1/4 inches to 4 inches in diameter, with showers typically measuring 2 inches. Lead pipes are rare except in homes built in the first years of the 1900s and earlier. If your pipe is lead, consult a plumber. Otherwise, your shower drain pipe is likely plastic, copper or possibly cast iron.

Step 2

Swirl a generous coating of pipe cleaner/primer around the outside of the pipe, encircling it three to four times, or as the product manufacturer instructs. Use the dauber inside the can, attached to the lid, to apply. Using a cleaner/primer removes oil, grime and other contaminants, allowing the cap to better seal to the pipe. In many locations, building code requires the use of a primer.

Step 3

Spread a generous coating of pipe cement -- if your drain pipe is either white PVC or gray ABS plastic products -- similar to how you applied the cleaner/primer. Swirl around the exterior of the drain pipe three times, then coat the inside of the drain plug fitting with another three rounds of cement.

Step 4

Fit the cap over the drain pipe and twist slightly to lock into place. A quarter turn is generally sufficient -- avoid overtightening, which may damage the pipe or connection. Leave the installation undisturbed while the cement cures and dries, as instructed by the manufacturer, or a minimum of 24 hours to be on the safe side.

Step 5

Slide a cap designed for a cast iron pipe down over the top of the shower drain pipe. If provided with the cap, push a rubber sleeve on first then follow with the cap. Tighten the metal strapping that encircles the cap, using a ratchet torque wrench to ensure an air-tight seal. Alternatively, use a screwdriver or other tool as directed by the manufacturer.

Step 6

Wrap a piece of 120-grit emery cloth around the exposed end of a copper drain pipe and work it back and forth -- both clockwise and counterclockwise -- for a minute or two to scuff the pipe's surface. Stop when the pipe begins to shine. Use a wire brush to treat the inside of the cap pipe fitting similarly.

Step 7

Brush on a thin layer of flux -- the soldering paste that seals the pipe fitting to the pipe -- around the exterior of the pipe using an acid brush -- a special paintbrush often used for adhesives, acids and other special solvents and solutions. Spread a thin layer around the inside of the cap fitting similarly. Immediately push the cap over the drain pipe and down until snug.

Step 8

Spread a piece of fireproof material such as a sheet of metal around the pipe to protect surrounding surfaces and prevent igniting a fire. Grab a fire extinguisher and keep it near if possible.

Step 9

Unroll a 6- to 8-inch long length of lead-free solder. Turn on a propane torch and adjust the flame to produce a strong, blue-centered cone of fire. Touch the flame to the pipe-and-fitting connection. Heat the connection for a minute or two to liquify the flux inside the connection.

Step 10

Touch the tip of the length of solder to the pipe beneath the cap, where the ridge forming the cap-to-pipe connection ends. Feed the solder to the pipe as it melts, as if you were writing on a cake with frosting. Encircle the entire cap-to-pipe connection with the solder -- a process known as "sweating the joint" -- and remove both the torch and the remaining solder when finished.

Step 11

Examine the joint, looking for holes or gaps, after the pipe has cooled a minute. Wipe away excess solder with a cloth and remove the heat shield before putting up your tools.


Sweating copper pipes is a job that takes practice to do well. In addition, it can be very dangerous if you don't know how to do it properly. Consider asking for professional assistance if you lack experience at sweating pipes.


Lead pipes are a health hazard, especially for the young, pregnant, or people with health problems. If your drain pipe is lead, you likely have other lead pipes in your home as well. If you suspect your pipe is lead, press your fingernail into it. A lead pipe will dent easily, like a sinker on a fishing pole line. If you pipes are lead, start by having your water level tested to see if it is within the levels allowed. If the level is too high, you should have all the pipes replaced. In that case, capping the drain pipe becomes irrelevant. If, however, your water is within safe levels, consult a plumbing professional to determine your best course of action.

references & resources

Karie Lapham Fay

Karie Fay earned a Bachelor of Science in psychology with a minor in law from the University of Arkansas at Monticello. After growing up in construction and with more than 30 years in the field, she believes a girl can swing a hammer with the best of them. She enjoys "green" or innovative solutions and unusual construction.