Sink unblocking, trap (u-bend) cleaning
If you need your sink unblocking then it may just be a case of cleaning your trap under the sink which stops foul smells from entering the kitchen from the kitchen sink waste pipework. Often food waste builds up over time and restricts the flow of waste water emptying from your sink, rice is a common food stuff which would cause a sink trap to block as grain by grain it builds up in the sink trap and also swells in size in the presence of water. If you cook lots of fatty meat and pour the fat down the sink then you may well have a more serious problem in the form of fat clogged pipes, gullies outside or drains. Also waste pipework that runs away at an incline may well cause a blocked sink as food waste will collect in the pipework and not drain away properly. Most of the time a blocked sink will simply require a plunger or the trap dismantling and cleaning of debris.
If the sink trap is blocked then the sink unblocking can usually be completed in 30 mins, if you have issues with pipework incline then it may take a few hours to re-plumb the offending pipework in order to run away correctly at a decline.