The kitchen sink line carries the worst load of any small drain in the house: hot fat that cools and sticks, food particles from the disposal, coffee grounds, rice and pasta starch, and dishwasher discharge full of detergent and more fat. It is usually 1.5 or 2 in in diameter, it often runs a long way to the stack, and in an older house it is galvanized steel that has been narrowing for sixty years. Kitchen lines block more often than any other branch, they block in a characteristic way, and a small-head camera shows exactly what has been going on inside them.
Quick answer: a kitchen line on camera shows a grease coating that narrows the bore from the top down, a bed of food waste and grounds in any flat section, and, in galvanized pipe, a rust lip at every fitting. The usual failure point is a long flat run or a belly between the sink and the stack where fat cools and settles. Cleaning restores the bore for a time; the camera shows whether the pipe is sound enough for cleaning to be the answer or whether the branch should be replaced with plastic at a better slope.
What goes down and what it does
Fat and oil leave the sink as warm liquid and cool in the pipe into a solid coating that thickens with every meal. The disposal sends fine pulp that would pass a clean line but sticks to a greasy one. Coffee grounds and rice do not dissolve and settle in any slow section. Detergent emulsifies some fat and carries it further along, which is why the blockage is often at the stack connection rather than under the sink. The combination builds a greasy, gritty tube that narrows month by month. The grease guide describes the coating; preventing grease blockages covers the habits that slow it.
What the camera shows
A pale, smooth coating thickest on the top and sides, narrowing the pipe to a slot of water at the bottom. A bed of grounds and pulp in any level section. In galvanized pipe, a rough brown wall under the grease and a lip of rust at each threaded fitting that the head bumps. In plastic, a smooth wall under the grease and glued fittings the head passes. A belly or a long flat run where the coating is thickest, which is the section that will block again after cleaning. And at the stack, a tee connection where the branch enters, sometimes protruding, where everything the detergent carried along finally stops. Dim the LEDs; a greasy wall glares. Camera inspection of a kitchen sink line covers the procedure.
Cleaning or replacement
A plastic kitchen branch at reasonable slope with a grease coating is cleaned, by cabling for a quick fix or by jetting for a thorough one, and the camera afterward shows a clean wall ready for another few years of use. A plastic branch with a belly or a long flat run is cleaned and then, if blockages are frequent, re-run at a better slope. A galvanized branch with a narrowed bore and rust lips is replaced, because the rust is the pipe wall and cleaning only delays the leak. The camera’s job is to show the material, the slope and the state of the wall so that the decision is made once rather than every six months. The galvanized guide covers the replacement case.
The disposal question
A disposal does not create the grease problem but it feeds it: fine pulp sticks to a greasy wall and builds the coating faster. A house with a chronic kitchen line problem and a disposal should run the disposal with plenty of cold water, which keeps fat solid so it passes rather than coating, and should keep fibrous and starchy waste out of it. A camera pass before and after a month of changed habits shows whether the habits are working.
Equipment
The kitchen branch is 1.5 or 2 in with a trap under the sink, so the camera is a 17 or 18 mm head on a 5 mm rod, entered with the trap removed. A long branch to a distant stack may need 100 ft of cable. A sun visor is irrelevant and a microphone is useful for noting the distance where the coating thickens. The 17 mm camera guide covers the options; a full-size 23 mm reel will not enter the line.
What to record
The material of the branch, the distance where the grease coating begins and where it is thickest, any flat run or belly, any rust lip, and the condition of the connection at the stack. A still of the thickest section. A note of whether the house has a disposal. That record decides between a cleaning schedule and a replacement, and it is the baseline the next inspection is compared with.
Common questions
Why does my kitchen sink keep clogging?
Grease coating the pipe, usually thickest at a flat section or at the stack. A camera shows how thick and where.
Can a kitchen line be jetted?
A plastic one, yes, with a small nozzle. A galvanized one may be damaged by jetting and is usually replaced instead.
Does hot water help?
It moves fat a little further along before it sets. Keeping fat out of the sink is the only measure that works.
Related guides
See hard water scale in drain lines, commercial kitchen grease line inspection, and the best sewer cameras for 1.5 in pipe.