How to unclog a grease-clogged drain

Where does grease come from?

Food

Grease, oil and fat are common by-products of a huge number of foods, e.g. Meat, dairy, rice, coffee grounds, eggshells and vegetables cooked in oils. Basically, anything that’s used for food prep or cooking can contribute to a grease-clogged pipe.

Even if you’re very cautious and keep your plug hole clean, you might not notice a growing build-up of grease in your drain pipe until it’s a much bigger problem.

Soap

Most soaps are made from either animal or vegetable fats, which behave in an identical way to the grease, oil and fat from food.

The soap fat clumps up with the fat from the food scraps and all together they conspire to cause your almighty stinking grease-clogged drain. (By the way, fat-free soaps are actually readily available – it’s just that not many people know about them!)

Where does grease accumulate?

Your kitchen sink is party central for fat, oil, grease, and grit – all of which are inherent in food waste. These are then carried down the plughole by water, flowing innocently down the sink – especially when there’s warm soapy water to ease its passage.

What’s happening lower down inside the pipe?

Lower down inside the pipe, warm water quickly cools and the water carries on flowing. However, the fats and oils start to solidify as they become exposed to the cold water and air in the pipes. Here, the grease tends to float on top of the water and over time it starts to coat the top of the pipe.

As more and more fats, oils and grease arrive down the drain, they build up and clog together. Eventually, this grease can completely block your drain, causing sudden overflows.

How do I know if my drain is blocked with grease?

Typically a blocked drain will begin to run slowly and make gurgling noises. You may notice a nasty lingering smell in the general area of the sink. These are your warning signs; so watch out for them and take the following measures to pre-empt a major blockage.

How to remove grease from drain pipes

The method you use to clear your blocked drain will vary depending on the severity of your blockage. We’ve listed the following five remedies in order of easiest and cheapest to the most difficult, costly or damaging to your pipes (namely, a chemical cleaner, which can be not only harmful to your pipes but to your skin and the environment).

1. Pour boiling hot water down the drain

If you do want to attempt to clear a grease clog yourself, and you know that your plumbing system is made up of metal pipes, not plastic, then you could try pouring hot water down the drain in order to flush it out.

If you have plastic pipes, this isn’t something we’d suggest trying as you could risk softening or melting the joints.

2. Hot water and vinegar

A 50:50 boiling hot water/vinegar mixture works in a similar way to a commercially available chemical drain cleaner (and is just as effective). The great thing about a homemade vinegar and water mix is that it’s non-toxic and much less corrosive than commercial drain cleaners.

The boiled water melts grease stuck to the inside walls of your pipes and the vinegar takes it away. Try following up a few minutes later with another dose if it doesn’t do the trick the first time around.

3. Use a plunger

A plunger works to force air through any standing water and dislodge the clog. This tends to be a short-term fix that cuts through the blockage for a short while but it doesn’t eradicate it as the above solution can.

4. Compressed air

You can use compressed air – or a CO2 drain gun – if you think your drain pipe needs some force to clear it. It essentially breaks up the blockage and pushes the remnants further down the pipe and far away. We recommend considering this as a last resort as the pressure increase using this method could cause compression fittings to separate.

5. Hydro sewer jet

If you’re experienced with one of these babies, by all means give this a try.

You can rent a hydro jet from a DIY shop, but if you’re not experienced and you’ve tried the above methods, we recommend you call a professional drain cleaner (they may use one of these). If you don’t know what you’re doing with a hydro jet, you may make a mistake, or even injure yourself.

What to do if your outside drain blocked with grease

If your outside drain is blocked, you might want to check whether it’s your responsibility or your water providers before you start delving into it.

How to prevent grease from blocking your drain

Prevention is always better than a cure. So just remember the following and you won’t have to worry about a grease-clogged drain:

• Don’t let fats, oils, grease, egg shells, coffee grounds or any food scraps go down the sink
• Scrape dishes into the bin before washing up
• Use a dishwasher instead of washing up. It’s way more efficient and economical
• Add a fat trap catcher to your kitchen sink. It’s a strainer made out of metal or silicone that lets water flow through to the drain but acts as a barrier to larger, more solid items. This is a game-changer and super cheap to buy online too
• Wipe dishes with kitchen roll before washing up. This is great for mopping up leftover grease that could cause the above problems
• Save your excess fats and oils from cooking and reuse them the next time you cook – waste not, want not
• Capture the fats by using foil or a suitable container. Once cooled you’ll be able to dispose of it at your local waste and recycling centre
• If you need to wash some particularly greasy dishes, you can soak them in a grease-dissolving or vinegar-based cleaner before you actually wash them. This way the grease will be gone before it even sees the drain

Sometimes you need a professional drain cleaner! If you find you’re plagued with persistently blocked pipes – perhaps you’ve just bought a property and need a professional opinion – you should definitely call in an expert to diagnose any problems and clear your drains.

Our plumbing and drainage insurance is extremely handy for homeowners and landlords, as drain issues can present some very tricky (and messy) problems if you try to sort them out by yourself.

Grease-clogged drain FAQs

What is the best drain cleaner for grease?

Our first recommendation is to try a homemade mix of boiling hot water and vinegar. It works just as well as a commercial drain cleaner, without the risk of damage, corrosion and harm to our environment.

How do you unblock a greasy sink?

Here are five alternatives to damaging caustic cleaners:
1. Pour boiling hot water down the drain
2. Use hot water and vinegar
3. Use a plunger for a short-term fix
4. Compressed air or a CO2 drain gun
5. Hydro sewer jet – only if you are experienced

What is the best homemade drain cleaner?

Use a 50:50 mix of boiling hot water and white vinegar. The hot water will melt the fat; the vinegar removes it from the lining of the pipes, and the flow of the water will carry it away down the pipe, so follow up with more hot water in a few minutes.