Making the Plunge
The most useful plumbing tool in your house probably lives in the bathroom, right next to the toilet. A plunger is a more powerful clog buster than most people realize, as long as you use it properly. To get the maximum force, the pipes should be full of water -- not air, which is compressible. This means filling the toilet or sink with enough water to cover the plunger. You should also block any drains connected to the one you're plunging with duct tape to prevent your efforts from dissipating into the atmosphere. This includes overflow openings on sinks and bathtubs.
Toilets are probably the most important plumbing fixtures in a typical house, and very few problems that affect them require the services of a plumber. Leaks are usually caused by a worn flapper or misadjusted float, both of which you can fix yourself without using tools. Some repairs, such as leaking around the base and dripping from the tank, involve removal and possible replacement of the toilet. Even that is a job most homeowners can handle, with the help of a wrench and a extra pair of hands for lifting. If you can't clear clogs with a plunger, a toilet auger usually does the job; if you don't have one, you can rent one.
It takes someone with plumbing knowledge and experience to handle water leaks under the house or inside the walls, but when the leak is in your sink or underneath it, you can usually fix it yourself. Faucets generally leak because an internal component -- often a rubber washer or gasket -- has worn out, and manufacturers make their products easy to disassemble so these parts can be replaced. Just remember to turn off the water before taking a faucet apart. If the drainpipes under a sink leak, you can usually repair them by unscrewing the nuts and refitting the pipes. A pair of adjustable pliers is all you need for this.
Clearing the Air
Sewer smells from a bathroom or kitchen sink are often the sign of a blockage in the plumbing vent pipes. These are an integral part of the plumbing system, supplying air to the drains through the vent pipe on the roof. When they get blocked, water doesn't flow freely and may create enough suction to empty a P-trap and expose the drain attached to that trap to the sewer. Clearing the vents is usually simple: Climb on the roof -- carefully -- inspect the vent opening, and remove any leaves or twigs blocking it. Spray water into the opening, and if it backs up, clear the vents with a rented auger.