What grease does in the pipe
Warm grease is liquid and seems to drain away easily. But a kitchen drain cools down quickly, especially in an outside wall or under the floor. The grease then sets against the inside wall of the pipe and forms a thin, sticky layer. Food scraps, coffee grounds and soap residue cling to that layer. Layer by layer the bore of the pipe gets smaller, until only a narrow opening is left.
Washing-up liquid loosens grease for a while, but further along the pipe, where the water cools and the detergent is diluted, the grease clumps together again. So washing-up liquid mainly moves the grease a little further along.
Where the build-up collects
Most of the build-up sits in the trap under the sink and in the first horizontal section of the pipe. There the pipe often has a shallow fall and the flow is low. The connection to the soil stack is another well-known spot, as is the transition from indoor to outdoor drainage. Where a dishwasher and sink share the same drain, warm water with grease and soap residue also comes through together regularly, which speeds up the build-up.
Disposing of grease properly in the kitchen
Here prevention really is simpler than cure. A few fixed habits will keep your kitchen drain clear for years:
- let frying and cooking fat cool, then pour it into a sealable bottle or jar for the collection point
- wipe pans and plates with kitchen paper before they go into the sink or dishwasher
- use a sink strainer to catch food scraps
- put coffee grounds in the organic waste bin, not down the drain
- run some hot tap water after washing up
Small amounts of set fat can usually go in the general waste. In many municipalities you can take larger amounts of frying oil to the recycling centre or a collection point. Check your municipality's website to see how this is arranged where you live.
What you can do yourself for a slow sink
If the sink is draining slowly, start by unscrewing the trap. Put a bucket underneath, loosen the nuts by hand and clean the part with hot water and a washing-up brush. Often there is already a sizeable plug of grease and scraps here. If the drain still does not run properly afterwards, the build-up is further along the pipe.
A plunger on the sink can help, as long as you cover the overflow with a wet cloth. We advise against boiling water from the kettle with plastic drains, because PVC can deform at high temperatures. Harsh chemical drain cleaners are not a good choice either: they attack rubber seals and older pipes and rarely dissolve a grease plug completely.
How an engineer cleans a greasy pipe
With a pipe that has grease build-up, simply poking a hole through the plug is not enough. A drain snake machine first restores the flow. High pressure jetting follows, with the nozzle loosening the grease layer from the whole pipe wall and flushing it away. As a result, the pipe has its full bore again afterwards. A CCTV drain survey shows whether the result is good and whether the fall is correct.
Bosmans Rioolservice works with drain snake and high pressure jetting equipment and gives a 2-year guarantee on the work. You hear the rate before the engineer drives out, with a call-out from 45 euros and work charged per hour.
Restaurants and commercial kitchens
A commercial kitchen sends far more grease down the drain than a home. That is why a grease separator is usually required there: a tank in which grease floats to the top and is captured before the water goes to the sewer. Even with a grease separator, build-up in the pipes before and after it needs attention. Bosmans provides maintenance for restaurants and businesses, with preventive jetting on a fixed schedule, so the kitchen keeps running smoothly on busy days.