Tools
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The tools needed for this task are the usual plumber's gear. A torque wrench in case you have to take apart a drain, a screwdriver, a plunger, a length of cable and rags to clean pipes and a hose to go after air bubbles.

If the U-bend of the drain is stopped up
With their constant level of water, U-bends are barriers against foul odors. If they clog, they do not work well.
Place a bucket or a receptacle under the clogged drain. It will collect the water and the waste matter that has caused the clog and the odor.
If the clog is between the U-bend and the pipe leading down from the sink, undo the register screw and with a wire or rubber tube, try to unclog and clean it.
If the clog was not there, it might be in the pipe that leads to the overall outlet pipe or to the siphon trap that collects waste water from throughout the house. Disassemble the U-bend and proceed in the same fashion with the wire or rubber tube, trying to clean out the pipe (generally it will lead toward the wall).
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The siphon trap
A proper system for getting rid of waste water in a home should be equipped with a siphon trap. They used to be made of lead, but these days they are made of hard plastic that is easy to clean.
If you avoid throwing solid waste into drains the siphon trap, also known as the U-bend box, usually does not clog. But if it does you have to take it apart. It is more than likely set somewhere in the floor of the bathroom.
The cover is removed with a screwdriver. You will then see that several pipes converge in a circular-shaped receptacle. The pipes will come from sinks, bathtubs, showers and appliances such as washing machines and dish washers.
�Wearing gloves, use a wire to try to unclog all blocked areas. Before closing it back up, pour enough water to see that the circuit works properly.
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Odors from the toilet
This is probably being caused by a clog in the drain pipe. This pipe tends to be much wider than water pipes and is not connected to the siphon trap. It is connected directly to the overall outlet pipe of the home.
Try using a stiff wire. If this does not work, use an old mop covered with a plastic bag. Bang it on the sides of the pipe.
There are also plungers bigger than those used for sinks, or probes that you can rent if the obstruction is serious.
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Eliminating air from pipes
When the water is cut off, it is common for the faucet to sputter or release little to no water when you turn it on. Generally this is resolved by leaving the faucet open for a while until the air bubbles are released.
Tapping gently with a hammer wrapped in a rag you may be able to dislodge stubborn bubbles stuck in areas with curves or joints that are not straight.
But if the problem does not go away and a faucet still sputters, there remains a bubble.
One way to fix it is to stick one end of a hose in the faucet (often the problem occurs in pipes where hot water flows)� and the other end in a cold-water faucet of the main system, normally the one from the sink, where the water comes out with higher pressure.
First turn on the problem-plagued faucet and then the cold-water one. The pressure from the latter should dislodge the bubble. If at first it doesn't work, keep trying.
If you have used a long hose be careful because in the end it will contain a lot of water.
If your faucets are single-command, giving both hot and cold water, take the pipe apart and cover it firmly with a cloth. Then open the hot-water faucet and finally the cold one.
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Tips
Take a few precautions to avoid a recurrence of foul odors and clogged drains.
Place a screen over all drains. Make sure neither hair nor food fall in.
Don't dispose of oil or chemicals down the kitchen drain.
Filters of home appliances like the washing machine or dishwasher should be cleaned periodically.
The toilet is not a garbage can. Only dispose of toil paper there.
If you have a country home or single family home, clean the drain pipes and sewer periodically. Otherwise odors or clogging could develop.

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