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The Best Ways to Clear an Outside Drain Blocked with Fat


When you have a drain that is blocked with fat from cooking you can experience severe issues, including internal or external flooding and damage to pipes and sewage systems. The primary cause of a blockage in a drain is oil, grease and fat that goes down the drain while preparing food. Fat deposits will collect together in large blocks over time, which people sometimes call ‘fatbergs’.

Fat will cause significant damage, as blockages can put very high pressure on the walls, drains, pipes and infrastructure of underground sewers – as well as internal plumbing. To see the real and lasting damage that fat and grease can do to drains and sewers you can view this short news report below:

You can clear an outside drain in many ways, and lots of these are quite easy to try by yourself. However, in some cases, a professional method of clearing the drain will be necessary. As experts in delivering high-quality drain repairs and dealing with blocked drains, we can recommend the best ways to clear an outside drain blocked with fat. In some cases, you may need to call a professional.

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5 Ways to Clear and Prevent an Outside Drain Blocked with Fat

The following are some helpful tips and good habits that will help to clear a drain that is blocked with fat, in addition to some useful methods of prevention. You can try many of these to help with drain blockages in other areas too.

The following are some helpful ways to clear an outside drain blocked with fat:

1: Pour Boiling Water Down the Outside and Kitchen Drain

A copper kettle blowing steam

Hot water will help to break up any blocks of fat when they are small and have not been building up for a long time. This is a good first step, as it allows you to determine whether there is a blockage within the internal pipes of the sink too.

Simply fill a kettle with boiling water and pour it down the outside drain and clean kitchen sink. Remove any strainer plugs or waste catchers before you do this. You can repeat the process multiple times and see if the water flow improves.

2: Use Caustic Soda

caustic soda flakes

Harsh substances such as caustic soda can provide an extra kick when unblocking drains, which you can try in a kitchen sink or outside drain. Caustic soda has the chemical name sodium hydroxide and causes reactions with acids.

You might find it difficult to know where to look for caustic soda, but it is available from many hardware shops and online. When hot water is not effective enough you only need to use a few tablespoons of caustic soda in the drain for it to work.

3: Try Drain Cleaners

Removal Of Blockage In The Sink

Drain cleaners are available in many supermarkets and convenience stores, usually alongside the other cleaning products and kitchen items. Drain cleaners often have a proprietary mix of substances with various cleaning chemicals.

There are many brands available with varying strengths, so try a stronger drain cleaner if the blockage is particularly bad or other methods have failed. Make sure you follow the instructions on your drain cleaning product for the best results.

4: Try a Drain Unblocker or Drain Rod

Homeowner using a sewer snake in outside drain

If the previous methods of clearing an outside drain blocked with fat fail, you can try bringing in some hardware. Drain rodding works by physically breaking the blockage out and can be effective. You will need a drain rod or drain snake.

Find the outside drain cover and insert the rod, then slowly unwind the drain snake, you may need one that is quite long depending on the location of the blockage. After this remove the rod and test whether the drain flows better.

5: Call a Professional

drain rodding

If the above methods do not work then a professional solution may be necessary. If you use a professional that can provide CCTV drain surveys then you can easily identify the location and scale of the problem to find the most reliable solution.

By using commercial-grade drain rods it is possible to clear up an outside drain blocked with fat very effectively. You will have the best result when using a professional solution, which is useful for restaurants and other businesses.

Clearing an Outside Drain Blocked with Fat Successfully

You can try the above methods, or a combination of them, to break up fat blockages in an outside drain. This can help clear the drain and unblock the fat deposits so that drainage is improved. 

Preventive methods also work well and regular cleaning will stop fat blockages becoming a problem in the first place. 

For a professional solution please feel free to contact us for a quote.