Fixture Drains
Each fixture in a plumbing system has its own drain line and each of the drain lines ties into a larger main line, which takes the water out of the house. Drains connected to plumbing fixtures are known as fixture drains and are usually found in bathrooms and kitchens. They’re also called traps because they do just that: trap water inside, preventing sewer gases from coming back into the house. Several connections are needed when connecting a trap.
At least one connection is needed installing fixtures–otherwise you could simply let the water run down a drain into a bathtub, sink or toilet. Fixture drains are designated FHA (Fixture Hotline Approval) numbers. Fixtures with FHA numbers were tested for connections, which is how it’s known what kind of connection is needed to hook up each fixture.
The standard connector allows you to attach another pipe to the trap arm, like when installing new fixtures within six feet of an existing one; most homes have this type of drain line already in place. The “wet vent” can be installed after FHA-approved appliances without connecting them to the fixture drain lines; instead, it lets out sewer gases all along its length–that includes bathrooms and–instead of back through any fixtures.
More On Fixture Drains
Each fixture has its own drain line; each of the drain lines ties into a larger sewer main line, which takes the water out of the house. Fixtures are usually found in bathrooms and kitchens, where there’s standing water left behind after cleaning yourself or dishes. They’re called traps because they do just that: trap water inside, preventing sewer gases from coming back into the house. Several connections are needed when connecting a trap. Fixture drains are designated FHA (Fixture Hotline Approval) numbers. Fixtures with FHA numbers were tested for connections, which is how it’s known what kind of connection is needed to hook up each fixture.
Branch Fixture Drains
Fixtures drain their water into branch fixture drains that are usually 2 inches in diameter, although they can be as large as 4 inches. Branch drains then supply the water to the main drain line–that’s usually at least 4 inches across–and are attached with a saddle hub connection. Saddle hubs have two openings for connecting pipes. FHA-approved FHAs use solvent cement, which is less expensive than using tee-fitting connections on laundry drains or on wet vented lines. Tee fittings have three openings for connecting pipes and FHA’s FHAs aren’t approved for this type of application because they stand up better against strong water pressure coming from multiple directions at once; too much pressure can burst through. Fixtures have FHA numbers for FHAs that are downstream in the drainage system, so all FHA fixtures in a house should attach to the main drain line by way of saddle hubs–and not tee fittings. Fixture drains must also be attached with solvent cement.
