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Frequently Asked Questions (FAQ) about Plumbing Traps and Drains
Sunday, March 13, 2022
Plumbing drains use gravity—the simple concept that water flows downhill—to do their work. But getting drain piping to function consistently without belching up sewer gas, clogging, or contaminating your drinking water is not so simple. Here’s some of the commonly asked questions about what plumbers call the DWV (Drain-Waste-Vent) system:
• Why is it a problem when a trap under a sink is installed backwards?
• Why is there a flexible accordion pipe under the sink?
• How do I get rid of the sewer gas smell in my house?
• What are the code requirements for plumbing vent terminations?
• What are the code requirements for layout of drain piping under sinks?
• What are the building code requirements for gray water reuse in Florida?
• What causes a gurgling sound when a bathtub or sink drains?
• What is the difference between a vent stack and a stack vent?
• What is a "combination waste and vent" in a plumbing system?
• Why is garbage disposal not allowed at a combination waste and vent (CW&V) under a sink?
• Is a washing machine drain hose required to be secured at the standpipe?
• What is an indirect waste receptor?
• What is the difference between water pipe and sewage (waste) pipe?
• How can I tell if a house is connected to a septic tank system or sewer?
• What type of water supply and drain (DWV) pipes were commonly used in the 2000s?
• What type water supply and drain (DWV) pipes were commonly used for 1990s residential plumbing?
• What type water supply and drain (DWV) pipes were commonly used for 1980s residential plumbing?
• What type water supply and drain (DWV) pipes were commonly used for 1970s residential plumbing?
• What type water supply and drain (DWV) pipes were commonly used for 1960s residential plumbing?
• What type water supply and drain (DWV) pipes were commonly used for 1950s residential plumbing?
• What type of pipes were used in 1940s homes?
• What type of pipes were used in 1930s homes?
• What type of pipes were used in 1920s homes?
• Should I seal the washing machine drain hose to the standpipe?
• Why is the European-style bottle trap not approved by the plumbing codes in the U.S.?
• What is an auto vent, air admittance valve, or check vent?
• Can I make a trap under the sink from straight pipe and 90º elbows?
• What are the pipes on my roof?
• What is a "cross connection" in a home's plumbing system?
• What is an "S-Trap" under my sink? Why is it a problem?
• What is the difference between gray water and black water in the plumbing code?
• Is a sink required to have a drain stopper?
• Can a laundry sink drain be installed without a trap under it?
• What is a drum trap at a plumbing drain?
• Can a dishwasher drain hose be connected after the sink trap (to the trap arm)?
• How far away from the sink can I install a dishwasher?
• What is a "high drain loop" or "air gap" in a dishwasher drain hose?
• What is the minimum and maximum distance a P-trap can be below a sink?
• Is an air admittance valve (AAV) legal by code?
• What is a double trap in plumbing?
• Does a home inspector check sewer lines underground?
• What types of plumbing traps are illegal by code?
• What is bell trap at a plumbing drain?
• How many plumbing vents through the roof are required by code?
• Can an air conditioning condensate drain pipe connect to a sink drain?
• What is the minimum and maximum slope of the trap arm of a plumbing drain?
• What is the minimum trap seal depth under a sink drain?
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