Tips for Buying a Property with a Septic Tank, Cesspit or Treatment Plant

Tips for Buying a Property with a Septic Tank, Cesspit or Treatment Plant

If you are considering purchasing your first property without a connection to the mains sewer then this guide is for you. This guide will also be useful to those who have not owned this type of property for a number of years as there have been several significant regulation changes and it is critical you understand your legal responsibilities. Here are our top tips to guide you through buying a property with off the mains sewage systems.

Know the regulations and your responsibilities

Familiarise yourself with the General Biding Rules for small sewage discharges, which came into effect on the 1st January 2015. As the property owner, legal compliance is your responsibility. The Environmental Agency (EA) provides a grace period of 12 months for new homeowners to ensure their sewage systems adheres to the rules. If your system does not adhere to the General Binding Rules and you do not have a permit, the discharge is illegal.

Read our guide on all the latest General Binding Rules here. 

Before purchasing the property, we would strongly recommend having the drainage system surveyed. The survey will be able to tell you whether the system complies with all the General Binding Rules and provides insight into the system’s overall condition. Investing in a through survey with a written report can save you from a potential costly surprise once you move in. At CountyClean Group, we offer home buyer’s and pre-purchase surveys across the South of England to help put your mind at ease and guarantee your drainage system doesn’t put the dampeners on buying your dream home.

Buying a house with a septic tank, cesspit or sewage treatment plant

What to ask the seller before purchasing the property?

The seller has a legal obligation to provide documented evidence to the following questions:

  1.  A description of the treatment plant and drainage system
  2. The location of the main parts of the treatment plant, drainage system and discharge point
  3.  Details of any changes made to the treatment plant and drainage system
  4. Details of how the treatment plant should be maintained and the maintenance manual, if they have one
  5. Copies of any maintenance or service records, if they have them.

If the seller of the property is unable to provide documented evidence of any of the above, it is advisable to consult your solicitor or seek a specialist to conduct an investigation and report their findings. The environmental agency’s General Binding Rules explicitly state:

“If you sell your property, you must tell the new operator (the owner or person responsible for the sewage treatment plant) in writing that a sewage discharge is in place.

Point 13 – Environment Agency General Binding Rules

What are the different types of off mains sewage systems?

Cesspits, also known as cesspools are simply holding tanks that store sewage without any treatment. Cesspits require regular emptying, and the effluent must be collected and disposed of correctly. Before purchasing a property with a cesspit, ensure you understand the regulations, the frequency it requires emptying and the costs entailed to empty and maintain the cesspit.

A septic tank usually consists of 1 to 3 chambers, designed to separate solids from the liquid. The liquid is directed into a drainage field where it filters into the ground. The solids are retained within the tank and require “pumping” out periodically.

To identify if a septic tank is installed at the property, you should be able to look into the tank and see an outlet. If you are unable to inspect the tank prior to purchasing the property, we would recommended asking the current owner for a copy of their emptying receipts. The typical cost for septic tank emptying ranges between £100 and £300 per year but this will depend on various factors such as the size of the tank and the size of the household.

Tips for buying a property with a cesspit, septic tank or treatment plant

The clue is in the name: a sewage treatment system, put in simple terms, treats sewage. It operates in a similar way to a septic tank but is more advanced and has moving mechanical parts to create an environment to facilitate the growth of bacteria.

The bacteria plays a crucial role in breaking down the sewage and solid materials, generating a clean and non-polluting effluent discharge. In some cases this treated effluent can be discharged into a waterway or absorption trench, provided all the relevant legal permissions have been obtained.

Check that the seller has had their sewage system emptied regularly

All sewage systems need to be emptied or ‘desludged’ regularly to keep the systems in optimal conditions. The frequency of how often you should have your septic tank being emptied will depend on a variety of factors, with the main one being it’s size. The smaller the tank, the quicker it will fill up and require more frequent emptying. The number of people in the household will also affect the frequency as more waste is being generated and going into the tank. To prevent any build-up, sludge and floating scum, it is recommended to have the septic tank emptied/pumped out once a year. Regular emptying and servicing is the cheapest and more effective way to maintain your septic tank system and keep it in top working order.

For sewage treatment plants, most manufacturers recommend having your sewage treatment plant emptied at least once a year. Although the purpose of a sewage treatment plant is to treat the wastewater as thoroughly as possible while dealing with much more waste than a septic tank, they still require emptying annually. Over time, the sludge can build up in the treatment plant so it’s beneficial that the sludge in the system is emptied annually or as advised by the manufacturer and installer to keep the sewage treatment plant in optimal condition.

As cesspits are simply a holding tank without an outlet, they do required to be emptied more frequently. It is recommended that cesspits should be emptied anywhere between bi-monthly and quarterly to avoid the build-up of solids. The actual frequency will vary depending on your usage and how many people live in your home.

Check that the seller has had their sewage system serviced regularly

Under current legal regulations. Most cesspits and septic tanks do not require official servicing. In contrast, sewage treatment plants, as per the Environmental Agency’s general binding rules; “must be installed and operated in accordance with the manufacturers specification”. Most manufacturers recommend annual servicing to ensure compliance with these regulations. Therefore, scheduling sewage treatment plant servicing at least once a year is necessary.

It is recommended to schedule an empty at the same time so your mechanical and electronic components can be serviced at the same time.


In conclusion, purchasing a property with a septic tank, cesspit, or treatment plant requires thorough understanding and careful consideration of legal responsibilities and system maintenance. Knowing the regulations, conducting a pre-purchase drainage survey, and asking the right questions to the seller are crucial steps in making an informed decision.

Tips for Buying a Property with a Septic Tank, Cesspit or Treatment Plant

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