If you’re looking at a property in a rural area (or even on the outskirts of town) there’s a good chance it won’t be connected to mains drainage. Instead, it may rely on a septic tank or private drainage system. These are incredibly common across Devon, but they do come with responsibilities that many people simply aren’t aware of until they’re already mid transaction.

Residential Property expert Daisy Otton writes about the considerations in this straightforward, no‑nonsense guide to what buyers and sellers need to be looking out for before, during and after their conveyancing transaction.

What is a Septic Tank?

A septic tank is basically an underground container where waste settles. Solids sink to the bottom, and the partially treated liquid goes out into a soakaway or drainage field. Because septic tanks only remove around 30–40% of pollutants, the law says they can only discharge to the ground, not straight into a river, stream or ditch. That kind of direct discharge has been illegal since 1 January 2020 (under the 2015 regulations).

If you hear “the septic tank discharges into the stream at the bottom of the garden”, that’s a red flag straight away.

Why this matters in your property sale and purchase.

1. Compliance With the General Binding Rules

The Environment Agency has tightened the rules over the last few years, and the latest version (updated October 2023) is something both buyers and sellers need to take seriously. These General Binding Rules apply to most private drainage systems in England and Wales.

A few key requirements:

• The system can’t discharge more than 2 cubic metres a day of domestic sewage.
• It must be regularly maintained and emptied, usually annually, by a registered waste carrier.
• It must not pollute ground or surface water or be located in a Groundwater Protection Zone (SPZ1).
• And most importantly, septic tanks can’t discharge into surface water. If they do, they must be replaced or upgraded (and this is where it can get expensive).

If a system doesn’t comply, you’re looking at potential fines, delays, stress, and in many cases, mortgage lenders refusing to proceed.

2. What Buyers Need to Be Aware Of

I always tell clients that a non‑compliant drainage system isn’t just a nuisance, it can be a serious financial burden.

Buyers may face:

• Unexpected upgrade or replacement costs.
• Ongoing servicing and emptying obligations.
• The risk of fines or enforcement action if the system pollutes.  

And do keep in mind that a standard homebuyer survey usually won’t get anywhere near the drainage system. A proper drainage survey, often with CCTV, is therefore the only reliable way of assessing what you’re actually buying.

3. What Sellers Should Have Ready

If you’re selling, you’re legally required to tell the buyer that the property has a septic tank or private drainage system. But more than that, you need to give them:

• A description and location of the system
• Details of the discharge point
• Any changes or upgrades
• Maintenance instructions
• Any servicing or emptying records you’ve kept
  
  

Buyers (and their lenders and solicitors) are getting much more cautious. A non‑compliant system may:

• Affect the value of your property
• Delay the sale
• Lead to last‑minute renegotiations or indemnity insurance requests
  
  

Being upfront and getting all of this information together at the start of the transaction saves a lot of stress down the line.

The Most Common Issues

1. Septic Tanks Still Discharging Into Streams

This is probably the single biggest problem, and it’s an automatic deal breaker because it is simply not allowed. The system will need to be replaced/upgraded.

2. Missing Maintenance Records

You’re not legally required to keep them, but buyers (and their solicitors) love seeing them. It gives reassurance that the system hasn’t been neglected and is in good working order.

3. System Too Small for the Property

If the house has been extended, or the number of bedrooms has increased, the original septic tank might no longer be sufficient.

4. Tanks Installed Too Close to Buildings or Watercourses

There are specific distance requirements — for example:

• 7m from buildings
• 10m from watercourses
• 50m from private water supplies

Our Recommendations

For Buyers:

• Get a drainage survey as early as possible, please don’t wait until the last minute.
• Check whether the system is shared and who maintains it.
• Make sure the system actually complies with the current rules.
• Request evidence of regular emptying and servicing.

For Sellers:

• Gather as much information as possible before going to market.
• Consider servicing or emptying the tank before listing.
• Locate the discharge point, you will be asked to confirm this!
• Deal with compliance issues early to avoid delays or renegotiation.

One thing I can’t stress enough, whether you’re buying or selling, is the importance of understanding the General Binding Rules (often called the GBRs). These are the legal standards set by the Environment Agency for small sewage discharges, and they apply to most septic tanks and treatment plants in England and Wales. They were updated in October 2023, so they’re very current, and enforcement is definitely tightening.

This is why getting proper advice early (and commissioning a specialist drainage survey where appropriate) is absolutely vital. It protects both sides from unexpected surprises later on and helps ensure your transaction goes as smoothly as possible.

Private drainage is one of those areas that often catches people out because everything is hidden underground, until you start the conveyancing process you may not even be aware of possible issues. But with the increased scrutiny from lenders and the tougher stance from the Environment Agency, it’s more important than ever to understand what you’re dealing with.

If you’re buying or selling a property with a septic tank and want clear, practical advice (minus the legal jargon), the residential property team at Wollens are always here and happy to help. If it should turns out that planning input is needed, for example, where a new drainage field, treatment plant, or system redesign may require planning considerations, Simon Rowland in our regulatory department (our planning specialist), is on hand to assist. Together, we can make sure you get the right guidance from both a conveyancing and planning perspective to keep your transaction moving smoothly.

You can also complete an online enquiry form. One of the Wollens team will contact you as soon as they are available.