Drain Problems and Repair Guides

How home drains work

Drains run the other way from supply pipes: they carry used water out of the house to the sewer. Under each sink is a trap, the U-shaped bend of pipe you can see in the cabinet.⁠[1] UF IFAS Extension says most sink clogs are in that trap, which is why it is the first pipe to open when a plunger fails.⁠[1]

Past the traps, the branch lines join and leave the house as one pipe, the sewer lateral. Los Angeles County Public Works describes the lateral as the pipe from the building to the main sewer line in the street, and says the property owner owns all of it, including the part under the street.⁠[2] Fargo, North Dakota, puts the same duty on owners up to the public main.⁠[3] Rules differ by city, so ask your utility where your part ends.

That layout explains the most useful rule in drain repair. A blockage in one trap or branch slows one fixture. A blockage in the lateral slows everything above it. Simsbury, Connecticut's sewer department says all drains backing up at once indicates a main sewer line issue rather than a single fixture.⁠[4]

Many drains also have openings that matter when you plunge: a bathroom sink's overflow hole, the second basin of a kitchen sink, and a dishwasher air gap. Korky, which makes plungers, plugs each one first so the pressure goes toward the clog.⁠[5]

Drain safety basics

Treat backed-up drain water as sewage. Fargo's water department warns that contact with household sewage is a serious public health risk and says to avoid it.⁠[3] Wear rubber gloves and keep children and pets away.

Common drain problems and the first check

Start with the row that matches what you see.

Toilets have their own guides. See toilet problems and repair guides.

Habits that prevent clogs

Keep grease out of every drain. LA County Public Works says fats, oils and grease harden and stick inside sewer pipes and can eventually block them.⁠[2] UF IFAS Extension suggests pouring used grease into a can to cool, bagging it and putting it in the trash, then cleaning the pan with hot water and detergent.⁠[1]

Use strainers. UF says to keep the strainer in the kitchen sink and clean it after each use.⁠[1] Oregon State University Extension adds coffee grounds and hair to the list of things to keep out, and says to pull out and clean bathroom pop-up drains regularly.⁠[7]

Run the disposer the way its maker says. InSinkErator grinds with a moderate flow of cold water, keeps it running a few seconds after grinding, and says never to pour grease or fat into the disposer or drain.⁠[8]

Flush only toilet paper. Fargo lists objects flushed down toilets and "flushable" products that do not break down, such as wipes, paper towels and diapers, among the common causes of sewer blockages. Tree roots in broken pipes and old pipe are on the list too.⁠[3]

Rinse drains that clog often. Korky suggests running hot water for a few minutes every couple of weeks in a sink that clogs regularly.⁠[5]

Go easy on chemicals. UF says chemical drain cleaners help only on sluggish drains, are caustic, can damage pipes and fixture finishes, and are bad for septic tanks.⁠[1] Oregon State's sheet clears a blocked drain without them: a plunger first, then the trap, then a cleanout auger.⁠[7]