Drain, Waste and Vent Plumbing
The waste system in your home consists of vents, drains and sewer line.
The drain and waste lines are larger diameter (3-4″) cast iron or plastic pipes. Their job is to remove waste water and sewage from the toilets and other fixtures to the main sewage lateral or septic system.
Vents are connected to the waste and drain lines to allow sewer gas to escape to the roof, and to prevent vacuums in the drain lines that might interfere with a smooth flowing line.
The sewer lateral is discussed on another page. Follow this link to my page on sewer lines to the street or septic system.
The waste system collects drain water from all the home’s various plumbing fixtures. Sinks, showers, bathtubs, toilets, washing machines, dishwashers and bidets are all connected through a lattice of pipe. The drain piping then delivers it to the municipal sewer line or to a septic tank system located on your property.
- Locate your main sewer line and find the clean outs along the route.
- If your home has a crawl space, have the main sewer line inspected. Ensure it is strapped and sloped properly and there are no breaks or leaks in the line. It is especially important to inspect the connections to the sewer lines and the toilets which are visible at the underside of the subfloor. Any leaks or water damage in these locations are important to have repaired ASAP. Report loose toilets ASAP because these will leak and damage the subfloor.
- Professional plumbers have advised me that in the case of a city sewer connection that it is good practice to leave an exterior clean out cap unscrewed. Do this somewhere between the house and the street as a precaution. In the event the main city sewer line backs up it will blow out of the unscrewed cap rather than flow into your home. YES, this can happen, and I agree with the professionals on this one. Better yet, just leave the cap unscrewed and off the most obvious clean-out. That way it will be noticed right away if there is an event like this.
- 1x per year: Run water through the sewer clean outs to ensure the free flow of material.
- 1x per 2 years: For those of you with septic tanks, every two years septic systems should have the leach fields rotated and every five years the tank should be pumped out and inspected.
See Septic in Utilities
How Drains Work
Almost all residential waste systems are designed to work on a gravity-flow basis. A downward slope of the pipe is the only power needed to move the waste water through and out of the house. Since gravity is the only mens of moving the waste water, sometimes really big or heavy debris, or a section of poorly sloped piping can result in clogging. When this happens a plumbing snake or water jet may be needed to get the system flowing again. Do not use chemical drain cleaners. Learn why here.
Homes with finished basements, or where the sewer lines are uphill from the structure must incorporate ejector pumps. These elevate the wastewater up to the sewer or septic line as needed. In cases where a sewage ejector is used, maintenance of the ejector and its power supply is critical. A back up generator and/or emergency battery power supply is highly recommended.
Vents are the mysterious little pipes that you see up on your roof. These pipes are counterintuitively exposed and uncovered to the elements. It is OK. These are open and exposed because they are connected to the house drain lines. Vents serve to allow air into and out of the drain system thus enabling smooth drainage and directing all kinds of foul sewer odors up and away from the house.
I once met a new client who was complaining that his house smelled like a sewer all the time. Apparently the home had been in that condition for years. None of the plumbers he had out could troubleshoot the problem. No leaks in the crawlspace, none under the sinks or behind the washer and all of the traps were filled with water and working properly. “You find the problem and I’ll be a customer forever.”
When I inspected the roof, I discovered all of the plumbing vents had been very thoroughly blocked off with duct tape. When I asked, the client confessed that he had done it, saying that he was afraid that “during heavy rains those open pipes up there would probably cause a leak.” I removed the tape in six minutes. Within a week the home had aired out fine, but carpet, drapes and clothing would not and had to be replaced. This person is still a client…and now a friend, and no, I won’t say who it was.
To keep you safe and sanitary, the government has developed a lot of building code details about the waste system in your home. There are codes about the size of piping and types of fittings. Codes details about where vents must be located and how many. Leave that to a professional plumber. As homeowner, this is nearly everything you need to know about the waste system of your home.