Do It Yourself: Bad odor might be traced to shower drain

Q. We get an intermittent bad odor, like sewer gas, from our shower drain. The drain flows freely, and if we pour bleach into it the odor goes away for a while, but it always comes back. The house is built over a crawl space, and we have not seen any leaks in the trap or drain pipe below the shower. What do you suggest?

A. There is a good chance the odor is caused by rotting hair and bacteria that have collected in the drain, even though the drain has not clogged (at least as yet). Remove the cover plate from the drain and put the plate and screws out of the way. You should then be able to “fish” down inside the drain with a piece of coat-hanger wire that has a small hook bent into the end. Even better, obtain a Cobra Zip-It drain cleaning tool. You can buy one at some home centers and hardware stores or on the Internet for less than $3. The tool is simply a strip of flexible plastic about 18 inches long. It has toothed edges that will snag debris and let you pull it out. The tool also works in sink drains, but won’t clean pipes beyond the trap. 

After removing any debris from the shower drain, pour in a couple of quarts of chlorine bleach and let it stand in the drain overnight. The bleach should destroy any odor-causing bacteria.

In the morning, flush out the bleach with very hot water, which will help dissolve grease. If this treatment doesn’t stop the odor, check again for leaks in the trap. Have the shower turned on while making this check so that water is passing through the trap.  If the trap does have a slow leak that you haven’t noticed, sewer gas could be seeping into the house.  

Q. I want to install some wall shelves that will hold heavy objects, including books. I intend to put the shelving on brackets fastened to the wall. How far apart can I space the brackets so that the shelves won’t sag under the weight? The walls are finished with drywall.

A. If the shelves will hold heavy objects, you should screw the brackets directly into wall studs. The maximum spacing depends on the strength of the shelving you use, but I think it would be a mistake to space the brackets more than 32 inches apart, no matter what shelving you use. As wall studs are normally spaced on 16-inch centers, this means you should screw a bracket to one stud, then skip a stud before attaching the next bracket.

If it is impossible to screw both brackets directly to studs, you will have to use special hollow-wall fasteners such as molly bolts to secure the brackets. Even if you use these special fasteners, do not overload the shelves. Also, don’t attempt to install heavy-object shelves on drywall using plastic anchors or other light-duty  fasteners.

You don’t say what type of shelving you plan to use, but even with a 32-inch span you should avoid particleboard (often sold with a plastic melamine covering). If you use three-quarter- inch pine shelving, you should reinforce the front edge of each shelf with a face strip about 1  1/2 inches wide, running along the entire edge. The face strip can be glued or nailed in place; it will stiffen the shelves to help prevent sagging.  Plywood makes fairly strong shelves, but three-quarter-inch plywood shelves should also be given face strips both for strength and appearance. Some home centers and lumber yards also sell poplar and oak shelving, which is more expensive but somewhat stronger than the materials already mentioned.