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Blocked Drains and Toilets

Why Do Drains Block and How To Unblock Them

Unblocking a drain

We all get blocked drains and toilets from time to time. But what causes our drains to block? What steps can we take to stop them blocking and how do we unblock them.

Here we look at blackwater, greywater and rainwater drains, and the toilets, kitchen sinks, washbasins, floor drains, showers and gutters that feed them.

We also look at the everyday things we use that cause blockages and what we can do to avoid blocking our pipes.

Finally we look at chemicals, plungers, pumps, hand tools and machines that are used to unblock our pipes.

If you have a blocked toilet or drain you can send a message to Awie:

WhatsApp on +62 (0)8123 847 852
Signal on +62 (0)8123 847 852

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In 2017 a sewer in London became blocked by a solid mass 250 metres long and weighing 130 tonnes. Looking like congealed fat and the size of an iceberg this mass is known as a "Fatberg".

Since 2010 Fatbergs have become a serious problem not only in the sewers of London but also in cities and small towns all around the world. They must be broken up and removed by hand, a process that costs a lot of money and can put the sewer out of action for many weeks.

Fatbergs consist of items that have been flushed down toilets and kitchen sinks but don't break down all held together by congealed fats, oils and grease (known as FOG) which go through the process of "saponification" in which the Fat, Oil and Grease turns into a soap like consistency. It is since people started widely using disposable wipes that the problem of fatbergs has become serious. Wet wipes are made from synthetic fibres and don't break down naturally.

In addition to the wet wipes fatbergs have been found to contain all sorts of items such as disposable nappies (diapers), toilet paper, sanitary items, cotton buds, needles, food waste and condoms.

In our normal lives we are highly unlikely to suffer from fatbergs but blocked drains are a common problem.

Home Drains

In our homes we have different types of drains which serve different purposes:

  • "Black water" drains carry sewage from our toilets. This must go to either to a septic tank for processing or to a sewer (if you are on the government sewerage system).
  • "Grey water" drains carry washing water from our kitchen sinks, washing machines, showers and washbasins. Grey water should also go to a septic tank or a sewer.
  • Rainwater gutters, downpipes and drains carry away rainwater. This can be discharged into absorption pits, flood drains, roadside gots (drainage channels) or, as long as it is clean, to rivers or streams.
  • Backwash water from water filtration and water softening equipment usually contains the minerals we find in our water but in very high concentrations, this is best sent to an absorption pit so the ground can filter out the minerals and return the water to the water table.

It is important to note that:

  1. It is illegal to discharge black or grey water into rainwater drains, roadside gots, rivers or streams.
  2. Rainwater should not be discharged into a septic tank or sewer. If, after heavy rain, you find your septic tank is overflowing you may find that someone has connected the rainwater drains to the septic system.


In The Past

It used to be that the most common cause of blocked drains were tree roots growing into rainwater drains and sewers and blocking them. In the past (and still used in Britain, Australia and other countries) external (underground) drains were made from ceramic pipes in which fairly short sections of pipe were connected using rubber "O" rings to seal the joints. Inevitably a bit of ground movement or poor installation and a joint would start to leak, tree roots would follow the water, find the leak and grow into the pipe eventually blocking it. To clear such a blockage a special cutter attached to a rotating long coil spring (a snake) has to be pushed down the pipe to cut the roots and clear the blockage. If this doesn't work the pipe has to be dug out and replaced.

Present Day

These days plastic is widely used for underground drainage pipes with sealed or welded joints. These don't leak so tree roots rarely cause difficulties however blocked pipes are still a regular problem. Around our homes drains can become blocked by sand, soil, leaves, cement or other debris. This is common after floods or especially while a house is being built or renovated.

The most common cause, however, is a result of the many things we flush down toilets and sinks and it is the Black and Grey water drains that are most likely to get blocked.

Hair, food waste, nappies (diapers), wet wipes, sanitary items, condoms and cotton buds cause the most problems. Many of these items are made from plastics and so they don't break down. They can easily get caught in a joint or bend in a pipe and we have the start of a blockage.

Fats, oils and grease can also cause serious problems. As they cool down, coagulate or mix with other substances they may change their chemical structure (known as saponification) forming a soap like consistency which can be very difficult to remove.

Grease and fat is a particular problem for restaurants and cafes which is why they always install grease traps to collect grease before it gets into the drains.

Hospitals sometimes have problems with bathroom drains becoming blocked by body fat and soap.

Many blockages start by simply going to the toilet. Toilet paper "scrunchers" are people who use lots of toilet paper and scrunch it up into a ball which can block toilets. Folded toilet paper flushes away far more easily while water spray washers are best with no personal contact and no paper waste to flush down the toilet.

How to stop drains getting blocked

  • Do not flush wet wipes, nappies, diapers, condoms, sanitary products or cotton buds down your toilet.
  • Do not scrunch toilet paper into large balls, either fold it or, better, use water spray.
  • Do not pour cooking oils or fats down the kitchen sink.
  • Remove leaves from gutters downpipes and drains.
  • Do not let soil, sand or cement wash into drains.

How to protect yourself from blocked drains

  • Make sure you have a plumber or MEP engineer to design and advise you about black, grey and rain water installations.
  • Install "U" bends on floor and shower drains, washbasins, kitchen sinks, and bath drains. Toilets have U bends built into their design.
  • Make sure drains are a large enough diameter. 4 inch for toilets, 2 inch for grey water.
  • Make sure drains have sufficient slope for the water to run correctly.
  • Use round bottom rather than square bottom drains. This concentrates the water flow in the bottom helping to keep them clean.
  • Keep bends to a minimum and use 45 degree bends rather than 90 degree bends in underground pipework.
  • Install "cleanouts" (access poiunts) in drains to allow access for pipe cleaning equipment.
  • In restaurants and cafes make sure you have a grease trap installed and clean it out regularly.


Chemical Drain Cleaners (or Drain Openers)

There are a number of chemicals available for unblocking drains which are acid or alkaline based. You pour the chemical down the drain, it dissolves the blockage to clear the drain. Alkaline cleaners usually contain sodium hypochlorite (bleach) sodium hydroxide or potassium hydroxide and they may be liquid or solid form. Acid cleaners usually contain sulphuric acid in high concentrations and are usually in liquid form.

To work effectively they must have high concentrations of very nasty chemicals. They work best for smaller, easy to access blockage such as washbasin U bends. They are not effective at dissolving blockages far from the drain opening. Solid forms need to be placed in close contact with the blockage itself (usually not possible) or they can actually make the problem worse.

My advice is don't pour these very nasty chemical into your drains, they are dangerous and can give serious burns, they can cause corrosion of metal pipes and fittings, they destroy the bacteria that make septic tanks work and are disastrous for the environment.

Plungers And Hand Pumps

The good old plunger (a rubber cap on the end of a wooden handle) can work well for small blockages not far from the drain opening of sinks, washbasins, toilets, floor drains. They may not fully remove blockages so recurrence of the blockage may occur. They are low cost, easy to use and can give very useful temporary relief. Everyone should have one.

Hand pumps are a more sophisticated version of the same device that generates more intense and sustained pressure to release a blockage.

U Bends

Make sure you have U bends fitted to all washbasins, sinks, floor drains and shower drains. Toilets have them built in. U bends have two functions:

  1. They provide a water trap to stop bad smells or bugs coming from the sewer or drain.
  2. They catch things (anything from sand, nail clippings to wedding rings) that may fall into the drain.

Blockages are often caused by U bends becoming filled up. First try a plunger to see if that will clear it. If not then with sinks and washbasins you can remove the U bend, clean it out and replace it. With floor drains you may be able to remove the drain cover to clean out the U bend. If you still can't clear it you probably need to call a plumber who has specialist drain cleaning equipment.

Snakes and Augers

Plumbers use Augers (steel rods) and snakes (long steel spring like cables) that they push down the drain to clear out blockages. Augers can only be used in straight sections of pipe while snakes can get around bends. In both cases operating lengths are limited.

Drain Cleaning Machines

To avoid having to dig up pipes, drain cleaning machines are necessary for clearing serious blockages. Two types of machines are used and both require skill and experience to be effective.

A. Water Jetting Equipment

Water jet cleaners pump water at high pressure through a high pressure hose that is pushed into the drain. I specially designed nozzle on the end has jets pointing backwards that pulls the hose into the drain and round bends. A powerful jet on the front breaks up blockages and can even cut through tree roots. Water jet machines can clear blockages many metres from the drain access point. The downside is that these machines use a lot of water which can end up flooding the room where the drain access is. These machines are best for outdoor drains with outdoor access.

B. Rotary Steel Snake Machines

These use the same principle as the hand held snake already mentioned but with a machine that rotates the snake. Sections of the spring cable can be added at will to reach blockages a long way from the drain access point and a range of different tools can be attached to the leading end of the snake to cut through or fish out blockage material.

Dig The Pipe Out

If all else fails then all that is left is to either dig out the pipe to clear it or to install a new pipe bypassing the blocked section.

A Final Word Of Advice

To successfully unblock drains without causing damage to either your drains or your house requires experience and the right specialist equipment. Make sure you have a plumber you can trust and will not charge an exorbitant fee.

Further Assistance


  1. you need further advice or
  2. you have as blocked toilet and you are in Bali

you can contact us here: Contact

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Copyright © Phil Wilson 17th October 2021
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