Everything you need to know about your old cesspool

Category: Septic system
24 Jan 2023

cesspool, also called a sump pit or a soakaway, is a hole in the ground surrounded by cement, stone, concrete, brick or other material and is used to collect wastewater from the house. The material used for the pit wall is sometimes perforated to allow wastewater to seep in from the sides. In other words, cesspools provide temporary storage for wastewater before it percolates into the ground. Originally, they were not connected to a septic tank. The wastewater was not pre-treated before being discharged into it. The wastewater was sent directly to the pit. So the cesspools were not as efficient as today’s septic tanks.

They did not have a mechanism to separate solids from liquids. Cesspools polluted groundwater much more easily. They also filled up much more quickly and required frequent emptying. All of these factors explain why sumps are no longer built on new properties. However, if you buy a house that was built a long time ago, you may find a cesspit.

How does a cesspool work?

As we have seen, the walls are made of several materials, but they all have in common that they are not completely watertight to allow water to seep in. Wastewater will seep through the bottom of the pit and possibly through the sides as well. Most cesspools also have a septic tank. The septic tank is used to hold back solids so that they do not accumulate in the pit. It is the septic tank that needs to be pumped out periodically, not the cesspit.

How to know if you have a cesspool on your property

Cesspools were installed in homes built before 1970. So, if your home is newer than that, it is very unlikely that you have one. That’s because government regulations prohibited the installation of sumps on new properties from the 1970s onward. If you are unsure of the age of your home and whether you have a cesspit or a drainfield, you can check your certificate of location.

Why were cesspools banned for new properties?

Old cesspools that were not connected to a septic tank posed a considerable risk to the environment and clogged very quickly. They did not treat the wastewater, but simply disposed of it in the soil. The wastewater was concentrated in one place. Wastewater that seeped into the ground was much more likely to contaminate the artesian well, the water table and other surface waters. This had various public health ramifications as well as other undesirable environmental impacts. Cesspools that were connected to a septic tank at least treated the wastewater before it was discharged into the sump. However, the absorption area was very limited and black sludge (biomat) also accumulated very quickly. The leaching bed solved this problem by increasing the surface area of the infiltration zone. This allows the effluent to be treated much more easily as it infiltrates the receiving soil and before it reaches the groundwater.


How to know if you have a failed cesspool

Contrary to popular belief, a cesspool does not have to be completely blocked for you to know that it is no longer functioning properly. Although this is one of the most obvious signs, it’s possible that the soakaway pit is still collecting wastewater even though it’s no longer functioning properly. Here are some things to look for when inspecting your cesspool.

  • The most obvious sign of a faulty sump is when the sump is full and can no longer hold the wastewater (either on the ground or inside the house).
  • There is when the pit has contaminated a stream, wetland or drinking water well.
  • It has when the liquid level in the septic tank is higher than the drain pipe connected to the cesspool.
  • There is when the bottom of the sump sinks lower than the water table, resulting in direct contact of the sump effluent with the groundwater (this is very dangerous and should be avoided at all costs).

A failing cesspool will pollute the environment and can lead to the proliferation of pathogens that cause various diseases. Any sign of system failure should be taken very seriously and corrective action should be taken quickly. We recommend a shock treatment, which is a method of introducing billions of bacteria into the cesspit by adding biological additives.

The bacteria will help to digest the organic waste and this will help the system to function optimally again.

Should I replace my cesspool with a leaching bed?

As long as your old cesspool is not polluting, the government allows you to keep it because it is a grandfathered right. However, it will be your responsibility to ensure that the sump pit does not cause any groundwater pollution. That said, it may be mandatory to replace your old cesspool with a new septic system under the following conditions:

  • If your pit is 200 feet (or less) from a public water well, body of water or any type of drinking water supply
  • If your cesspool serves non-residential facilities or if your home becomes a multi- family dwelling.
  • If your cesspool overflows and contaminates the environment

How much does it cost to replace the cesspool?

Replacing a cesspool with a new septic system will cost between $10,000 CAD and $30,000 CAD. However, not all sumps can be replaced with a conventional septic system. On small properties and those near wells and other water bodies, it may be necessary to install an advanced treatment system instead. In addition, you may need to use a tertiary treatment system with a UV lamp to reduce fecal coliform levels. Advanced systems add a layer of treatment to the system. They cost more than conventional systems. An engineer will advise you on the type of septic system that is best for your property.


If your home was built before the 1970s, chances are you have a cesspool on the property. As long as the sump is a good distance from a drinking water source (at least 200 feet) and is not polluting the environment, you have nothing to worry about. Of course, you still need to be careful to monitor your system and maintain it properly to avoid any form of failure. However, it’s a good idea to plan to replace your old cesspool with a new septic system, as it will better treat the wastewater. Replacing the soakaway pit with a new septic system may seem costly, but considering its age, it will unfortunately be unavoidable in the years to come.

About the author


CEO at Bio-Sol

Our goal is not only to offer you the best products on the market but also to educate and empower you with the insights you need for successful wastewater treatment.


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