8 things to check when buying a house with a septic tank

Buying a house with a septic tank might seem like a infrequent concern, but if you're looking to live in the countryside, it might become a very real possibility.

Properties without mains drainage typically rely on a septic tank to deal with sewage and wastewater, although some may have an open cesspit. Between 300,000 and 500,000 homes in England and Wales have septic tanks, according to the Environment Agency, which conducted research of likely locations in 2009.

Meanwhile, you are unlikely to encounter this in urban areas in the UK as homes in these locations are more likely to be connected to utility company sewerage systems.

Here are eight of the key things to check if you are buying a house with this type of off grid drainage.

1. The key facts

Your conveyancing solicitor should establish key facts about the septic tank. These include its location, when it was installed and when it was last serviced. Warranties and indemnities relating to the construction and maintenance of the septic tank should also be verified.

Your solicitor should also find out if the septic tank is shared with other properties.

“Shared septic tanks add complexity to property transactions due to the need for a detailed agreement which outlines responsibilities, management protocols, and financial arrangements,” says Lucy Hawkins, senior associate director at Strutt & Parker. “These documents are usually called Shared Septic Tank Agreements and while such agreements may slow a sale down, they are vital. There are even some benefits to having a shared tank rather than having sole responsibility, including lower individual costs and collective oversight for maintenance and repairs."

They will also check necessary planning permissions and building regulations approval have been obtained. In January 2020, new laws were introduced to prevent septic tanks causing pollution, particularly relating to watercourses and land, see p.2 below.

Lucy Hawkins

Lucy Hawkins has more than a decade of experience, starting her career in Cambridge before transferring to the Cirencester office, where she is also part of the Cotswolds consultancy team.

As a charted rural surveyor, Lucy specialises in residential, agricultural and commercial properties. Her expertise covers everything from property diversification and valuation, to equine property consultancy, landlord/tenant matters and prime lettings.

2. The specialist survey

Usually called a septic tank home survey or a septic tank inspection, this is a service carried out by a specialist firm to identify any problems and check that the tank complies with current legislation.

The surveyor will check the following; the exterior of the tank for cracks, corrosion and any other structural damage, that the size is suitable for the number of people living in the property, for the presence of leaks or blockages and that the tank is not discharging into a water course or surrounding land.

During the survey, the septic tank will be emptied thoroughly to check the flow works properly. Many surveyors now use CCTV to help their investigations.

In England, the surveyor will also find out if the septic tank is lawful, meeting the General Binding Rules for small sewage discharges (SSDs), which protect rivers and streams from pollution caused by septic tanks and other small-scale sewage treatment plants. The rules are quite complex and depend on the date the system was installed. Separate legislation applies in Scotland, Wales and Northern Ireland.

“Problems which may be incurred by an old septic tank include it going into the water course, which is a big no-no, or if the pipes are old, cracked or damaged, they will need replacing,” says Paddy Pritchard-Gordon, director of buying agency Prime Purchase.

“To replace a septic tank will cost anything from £10,000 to £15,000 so it’s well worth paying on top of the standard survey, so you know what you are dealing with.”

Prices for a septic tank survey range from £250 to £300, with the average at £275, according to Checkatrade.

Paddy Pritchard-Gordon

Paddy Pritchard-Gordon studied at Cirencester Agricultural College before working in the racing industry and then becoming an estate agent. He worked as an estate agent for a national agency for 24 years, firstly in London and then in East Anglia, before joining Prime Purchase this year to advise clients buying homes in Cambridgeshire, Norfolk, Suffolk, Hertfordshire and Essex.

3. A possible asking price reduction

Armed with your survey results, there might be scope for asking the sellers to drop the asking price. “There can be a lot of environmental issues created by septic tanks and if there is a problem with the one you are buying, you should get the cost of rectifying the situation deducted from the purchase price,” says Paddy.

“Another option is for the vendor to do the necessary work themselves. But if you are about to exchange contracts, there is a limited timeframe for such works. More realistically, the cost of repairing or replacing the tank should come off the purchase price, with the work done by the buyer.”

4. Is access good?

It is really important for a septic tank to have good access because it will need regular emptying, the sludge removing and any maintenance attended to. You’ll need to be sure that there is plenty of space for the pumping vehicle to operate efficiently, or you may have problems finding a company to carry out the job.

5. How often does it need emptying?

The frequency of septic tank emptying depends on the type and size of tank, as well as its usage, but typically, for most households it should be emptied annually. “For a standard 1,000-gallon septic tank, expect to pay around £200 per emptying,” says Lucy Hawkins. “Regular maintenance not only prevents costly repairs but also ensures the system operates efficiently, protecting both the property and the surrounding environment."

6. The benefits of having a septic tank

Septic tanks, properly maintained, are eco-friendly as they don’t generally use any form of chemical to filter waste. They may include an electric pump to conduct the wastewater to the drainage field, but apart from that, require no energy.

“Another key benefit is their cost-efficiency as homeowners avoid paying monthly sewer fees in their water bill,” says Lucy Hawkins. “Septic tanks also provide a level of independence, allowing homeowners to avoid reliance on the public infrastructure, which can be especially beneficial in remote or rural locations.

Modern septic tanks are highly durable and, with regular care, can last for several decades, Lucy adds: “This makes them a reliable and long-term solution for waste management.”

7. The disadvantages

“The regular maintenance, including emptying and inspections, can add up in costs over time, but it’s vital to stay on top of it, as any type of repair is expensive,” says Lucy Hawkins. “The capacity of a septic tank can also be limited, which means overloading the system or disposing of waste incorrectly can lead to blockages, leaks, or even system failure.

Bear in mind too, that a septic tank demands sufficient space for both the tank itself and the accompanying drainage field. If you’re buying a property which you wish to extend, or develop the garden, this can be a prohibitive factor.

8. Future problems

Septic tanks do require vigilance. The sludge in the bottom needs to be removed regularly to prevent clogs and blockages in the soakaway.

The household also needs to be reminded that putting certain items, including disposable nappies, feminine hygiene products, wipes, coffee grounds and cat litter down the WC, or sink, can cause clogs.

Structural issues can also occur. The tank may crack or even collapse, causing serious leakage and allowing groundwater in, which will contaminate the system.

Buying a property with a septic tank can bring challenges, but it’s often part and parcel of living in a rural location and is not uncommon. It might also be worth taking a look at off-grid heating options as well as other off grid drainage types.