Now that we have gone over how water gets in your house, it circulates throughout, and is warmed, its time to discuss how it leaves your home. This will be the last weekly recurring post of this series, however, I will continue to do posts about other plumbing related issues such as how to fix a toilet that constantly is running or how to unclog a sink.
What leaves your home is referred to as waste or the waste system and it has two parts: the pipes that take the fluids away from your house and the vent system that removes the associated odors as well as provides air flow that enables the pipes to function properly. Every plumbing fixture in your home has a drain. These drains are attached to a stack, which is a pipe that carries the used water down to the basement, and a vent that allows air to flow up and out through the roof. Once fluid is used, say from a shower, it travels down the stack to the basement and out the main sewer line. The main sewer line runs at a pitch towards the street where it meets the municipal sewer line or a private septic system. The slope of the main sewer line is very important as you want dirty liquid to travel away from your house rather than towards it (roughly a 1/4 slope down for every foot of sewer line). Somewhere before the main sewer line hits the municipal line, there exists a trap, which is a U-shaped pipe. It is often a good idea to install a check valve on your house's side of the trap. This check valve stops a clog and subsequent back up in the municipal line from entering into your main sewer line/basement.
To properly maintain your waste system, once a month pour a cup of regular bleach down each sink and tub drain. This will break down much of the built up debris. Also run your dishwasher once a month empty. The hot water will flush out the pipes both within the dishwasher and those that lead from the dishwasher to the stack. Finally, if you are really hard on your pipes (flush things that shouldn't be flushed, clog sinks regularly, put grease down the disposable etc.) you can have your waste pipes water jetted. Essentially, a company will come and insert a pipe into your waste line and flush the system with high pressure water.
I hope you have enjoyed this first Know How series!