buying house off mains drainage

Are you considering buying a house that is in an off mains drainage area?  Here are some key points to consider and questions to ask before making that big decision!

As a homeowner, you are responsible for ensuring that any off mains drainage system is not causing environmental harm or pollution.  Failure to comply with regulations may result in fines, so it is vital to ensure that your system complies.

Gaining knowledge and having the necessary information will facilitate a more seamless decision-making process, preventing unexpected surprises post-sale.

Know the System

Identify the existing system in place.

  • Questions to Ask

    • What system is currently in place?  For example, septic tank, sewage treatment plant, converted septic tank or cesspool?
    • How old is the system that is in place?
    • Is the system just serving the property you are looking at, or is it a shared system?  If shared, is there currently an agreement in place with regards to maintenance, repairs or replacement?
    • Does the existing homeowner know where the rainwater and surface water is going to?  Is it combined with the foul, or on its own setup?

Inspection is Key

Before sealing the deal, get a thorough inspection of the system.  Ensure it’s in good condition, so there are no hidden issues that may cost you later.

  • Questions to Ask

    • Has a home buyer drainage survey been carried out?
    • Does the system comply with the General Binding Rules (GBR)?  Make sure the system complies with rules and regulations.
    • Look for signs of soggy ground or unpleasant odors.

Size Matters

Understand the size of the system.  It should be appropriate for the size of the household to avoid overloading the system.

  • Questions to Ask

    • If it’s a sewage treatment plant, what ‘person equivalent’ is the unit?
    • If it’s a septic tank or cesspool, how many litres does it hold?

Maintenance is a Must

Off mains drainage systems require regular emptying and maintenance.  This will be specified by the manufacturer or building control.  Get an idea of the system’s history.  A well-maintained system is less likely to cause headaches.

  • Questions to Ask

    • Has the system been regularly maintained and emptied?
    • Request paperwork that confirms regular maintenance and emptying of the system.
    • Does the current homeowner have any pre-existing maintenance agreements in place for the system?

Location, Location, Location

Know the location of the system, and where it is discharging to.

  • Questions to Ask

    • Are there any parts of the system that are located outside of the property’s boundaries?
    • Where does the current system drain to, for example, drainage field, ditch, borehole?

Budget for Repairs

Like any system, off mains drainage systems may require repairs.  Be prepared financially for unexpected expenses, and consider adding a contingency to your budget.

  • Questions to Ask

    • What do the existing homeowners pay currently for emptying, maintenance, power, etc?
    • Have they recently had any repairs carried out on the system?

Being informed is crucial when buying a house in an off mains drainage area.  Do your due diligence to purchase your off mains drainage property with confidence.

Contact us for advice

If you would like some advice, please contact us on 01255 853890, or email  We provide a free site survey to provide advice on the best solution for you.