Cooking Oil, Fat and Your Kitchen Drain

Why fat blocks drains

Hot oil and fat run down the sink easily, but as they cool in the pipe they set like candle wax. Over weeks and months, a layer builds on the pipe walls. Rice, noodles, vegetable scraps and coffee grounds stick to it, and the pipe slowly narrows until water backs up in the sink or bubbles out of the overflow gully outside.

Washing-up liquid and hot water do not solve the problem. They carry the fat a little further before it cools and sets again, often in a part of the pipe that is harder to reach.

The habits that help

• Let pans cool, then wipe out oil and fat with paper towel and put it in the bin.
• Pour larger amounts of used oil into a sealed container and put it in the rubbish, or take it to a cooking oil collection point.
• Scrape plates into the bin or compost before rinsing.
• Use a sink strainer and empty it after every wash.
• Run the dishwasher with full loads and keep its filter clean.
• Never tip fat into the toilet. It blocks the sewer just the same.

Warning signs

A kitchen sink that drains slower each week, a gurgle when the sink empties, a smell from the plughole or water rising at the gully outside the kitchen all point to fat building up. Catch it early and the fix is quick.

What a plumber does

For a fat blockage, a high-pressure jetter is the best tool. It scours the pipe walls clean rather than just poking a hole through the middle. We then check the line with a camera to make sure there are no sags or breaks that will catch fat again. For homes that cook heavily every day, a jetting service every year or two can keep the line clear.

Avoid chemical cleaners

Caustic drain cleaners can turn fat into a soapy plug, damage older pipes and burn whoever clears the drain next. If the drain is badly blocked, call a plumber instead.

For food businesses

Restaurants and takeaways need a grease arrestor that is the right size and pumped out on schedule. Even then, kitchen lines before the arrestor need regular jetting. See our grease trap page for more.

Springvale ground and pipes

Springvale sits on a mix of sandy loam and heavier clay, and much of the suburb was built in the 1950s and 1960s with earthenware sewer pipes and galvanised or early copper water pipe. Clay joints shift over time and let roots in, rusting galvanised pipe slowly narrows and leaks, and drains under subdivided blocks are often shared between homes. We use drain cameras, locators and pressure tests to see exactly what is going on before anyone digs.

Related services

• Emergency plumbing
• Blocked drains
• Hot water
• Gas fitting
• Hot water replacement
• Heat pumps
• Leaking taps
• Burst pipes
• Toilets
• Leak detection
• Pipe relining
• Stormwater
• Bathrooms and kitchens
• Commercial plumbing
• Grease traps
• Backflow testing

More guides

• Kitchen fat and drains
• Find your water meter
• Roots in sewers
• Overflow relief gully
• Hot water for big families
• Gas heaters and CO
• Grease arrestor checklist
• Water pressure
• Running toilets
• Burst pipe first steps
• Stormwater on flat blocks
• Backflow for businesses