Complete Guide:

Selling a House With a Septic Tank (2023)

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Many houses in the UK (half a million, in fact) are not connected to the sewerage system. 

If your house is more than 50 meters from a mains sewer, you might have a septic tank on the grounds. 

Septic tanks deal with all wastewater from the house. 

This includes water from the sinks, baths and showers, kitchens, and toilets. 

There are a few things you need to be aware of if you’re selling a house with a septic tank.

Laws relating to pollution changed recently, and you’ll need to make sure your septic tank is up to code. 

This guide will walk you through what this means exactly, and give you actionable advice on selling a house with a septic system.

Table of Contents

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1. How to sell a house with a septic tank?

Some septic tanks are essentially storage units. 

Every 3-5 years, sewage will be collected by a drainage contractor. If your wastewater is collected, you don’t need to worry so much about the new regulations.

Many septic tanks, however, drain into ditches, rivers, tidal waters, or soakaways (drainage fields). 

In this case, the best thing to do is to replace your septic tank with a modern sewage treatment plant. 

This means the discharged wastewater will be properly treated, and much less harmful to the environment. 

You’ll be complying with Environmental Agency regulations which will be a huge help to your sale. 

2. What are the new laws for septic tanks?

Septic tank laws changed on the 1st of January 2020. It’s now illegal to allow wastewater to drain directly into a river, stream, or pond. 

This is to prevent dangerous bacteria harming people, fish, wildlife, and natural ecosystems. 

Because of this change, many septic tanks across the country are now out of date. 

You’ll need to make sure that your wastewater is being processed safely to comply with General Binding Rules (more on these below).

Homeowners were given 12 months from the 1st of January 2020 to update their sewage systems. 

If you’ve not yet done it, you’re risking fines and even prosecution from the Environmental Agency (EA). Because these fines are unlimited, it’s just not worth the risk. 

If you need to sell a house with a septic tank, it’s even more important to update your septic system. It’s one of the first things your buyer’s solicitor will ask about. 

3. What are General Binding Rules?

General Binding Rules are regulations set out by the Environmental Agency. They ensure peoples’ drainage systems aren’t causing harm to the local environment. 

You can find the full set of rules on the government website

If you don’t comply with General Binding Rules, the Environmental Agency can take action to issue fines and even take you to court. 

Remember, there is no limit on the fines you can receive.  

On top of this, you’d also need to pay for a ‘clean up’ operation. 

This is where specialists clear any pollutant substances from the local environment. 

This can be very expensive. The costs are likely to far outweigh those of installing a new septic tank.

If your septic tank has caused pollution because of a faulty installation, the installers may well be held responsible instead of you. 

If you’ve done everything right by hiring a professional fitter, you shouldn’t have to worry. 

The fitter can be fined and/or prosecuted if they’ve failed to do the job properly.

4. What can I do if my septic tank doesn’t comply?

There’s no need to panic if your septic tank drains directly into a water course.

If a septic tank has been fitted in the first place, it’s unlikely you’ll be able to connect to mains sewage draining. 

Sewage systems rarely change. But it might be that new development has extended the sewage network, so it’s worth checking. 

In the likely scenario you’re not near enough to mains sewage to connect, there are two routes you can take. 

  • Install a new septic tank or sewage treatment plant.
  • Divert the course of the wastewater.

Modern sewage treatment plants are different from septic tanks. 

They treat the wastewater, as opposed to separating it. Which type you choose will depend on your budget and also the status of your land.

Your installer will be able to advise you on which model is best.

Installing a new septic tank

This is the most common option, and often the best. 

Modern sewage treatment facilities are much more efficient than old-style septic tanks. 

They actively treat the water, meaning everything that comes out is safe and non-pollutive.

This means that even if your wastewater is still draining into a nearby water source like a river, it won’t cause any harm. 

New septic tanks and sewage systems come with certification. 

There are certain standards they have to meet to satisfy the EA’s requirements. 

These are really important to be aware of, but it can get a little complicated. See section 5 – ‘Understanding septic tank certification’ for more info. 

Diverting the course of wastewater

This option is only possible if you have spare land to use as a drainage field. 

Known as a ‘soakaway’, this method involves diverting wastewater into a large area of natural soils. 

The nitrates and minerals in the soil help to slowly break the waste product down over time. 

Unfortunately, natural soil drainage tends to be poor in developed areas. 

This means that even if you install a system to divert wastewater from a stream or ditch to a field, it might not pass environmental tests.

Before going ahead with an installation, you’d need to check that the land is not in a Groundwater Source Protection Zone. 

You can find this out with the EA’s postcode search tool

You’d then need to have a Trial Site Assessment and a Percolation Test

These test the suitability and absorbability of the soil. 

It’s almost always easier and cheaper to install a new sewage treatment plant. 

Diverting wastewater involves so much testing, digging, and underground pipework. 

What’s more, there are often much better things you can do with spare land than turning it into a soakaway. 

5. Understanding septic tank certifications

New septic tanks and sewage treatment plants must comply with BS EN 12566-3 Certification. You might like to take note of that number so you can check it with your installers.

Naturally, all installers will be aware of the rules. They should provide septic products that meet this standard. 

However, there’s something else that’s important to check.

The above 12566-3 Certification only measures the system’s ability to reduce pollutants. It doesn’t guarantee the output is safe enough for Environmental Agency standards.

Selling a house with a septic tank

Also, the 12566-3 Certification can be based on systems for 4-person houses or 6-person houses. 

So if your septic system has been tested to handle a 4-person household, it might not meet the requirements for a family of 6. 

So again, you might have the certification, but if the septic tank is overused it can harm the environment.

What you’ll need to do is ask for the manufacturer’s independent test reports. 

Here’s another set of numbers to write down: 20:30:20 (BOD:SS:NH3). 

This is the measure of a septic tank’s ‘effluent standard’. 

This is the standard the EA requires. Having the 12566-3 Certification doesn’t guarantee this standard. So it’s best to have both.

It sounds complicated, but all you need to do is take note of those two sets of numbers, and ensure your septic tank installers are complying with them. 

6. Am I responsible for my septic tank or is my buyer?

The truth is there’s no official answer.

As with many things relating to selling a house, there might be some negotiation on who actually makes the repairs or upgrades. 

Your buyer (or their solicitor) may insist that the septic system is brought in line with current regs before the sale can complete. 

Or, you might choose to put the house on the market flagging that the septic tank will need updating. 

Whatever is agreed will become a ‘condition of sale’ as part of the legal paperwork. 

The latter option might be appropriate if you’re selling the house as a renovation project. 

In that case, the buyer will come into the situation already prepared to do major works. 

It would also be appropriate if you’re selling through probate. 

Selling a house on behalf of a family member who’s died can be very emotionally challenging. You might be busy coordinating things like the will and the funeral. 

You’ll likely be less familiar with the property than if it were your own. It’s fair to ask your buyers if they’re prepared to do the work themselves.

If neither of these situations apply, your buyers might not be prepared for the time and expense. 

Insisting that they take on the burden might cause tension during the conveyancing process. 

If you’re still unsure, your solicitor will be able to advise you best.

7. Is it best to sort out my septic tank before I sell?

As a general rule, it’s usually best to ensure major facilities on your property are in good working order before you go to market.

Conveyancing is a complicated and lengthy process. 

Unnecessary disagreements can result in delayed completions and even sales falling through. 

This can be costly in terms of both time and money.

If you’re selling a house with a septic tank but can’t agree on who replaces it, you might be able to make an arrangement or compromise. 

For example, your buyers might offer you £5,000 – 10,000 under your asking price to cover the cost of replacement.

Or you might agree to cover the expenses if your buyers coordinate the works.

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Either way, you’ll need to provide details of the septic draining system to your buyers’ solicitor. It’s now a legal requirement to provide this in writing. 

They’ll ask for as much paperwork as you can provide, like invoices for maintenance, and your home-buyer’s drainage survey if you had one when you bought the property.

You’ll need to disclose things like:

  • Where the tank is located on the property
  • Where it drains to
  • How old it is
  • Details about the manufacturer, servicing, and any past changes or repairs
  • When the system was last emptied.

It almost goes without saying, but if you’ve decided to go ahead with a septic tank repair or replacement prior to selling, keep your receipts!

You’ll also be given a warranty which will be reassuring to your buyers, and useful for their solicitor. The more information you can provide, the less of an issue the septic tank will be.

8. How will my buyers know if the septic tank needs replacing?

If you have a septic tank, it’s almost guaranteed your buyers will ask for a survey. 

Especially if the property is very old, as is often the case with properties off the mains utilities system. 

Your buyers will need to have a ‘homebuyer’s drainage survey’ to assess the state of the tank (a standard building survey won’t cover it). 

It’s very common for your buyer’s solicitor to request one of these on the buyers’ behalf.

In this event, a surveyor will visit to drain the tank. 

They will check its condition and that it complies with current laws. 

Either way, if you’re selling a house with a septic tank on the property, you must tell your buyers it’s there. 

Your estate agents will need this information too. Honesty is always the best policy. 

Properties in some of the UK’s most desirable locations, like the New Forest and the Lake District, often come with off-mains drainage. 

So don’t worry about putting people off. Most people are aware that older, more rural houses often come with off-mains facilities.

9. How much does it cost to install a new sewage treatment plant?

According to CheckATrade, the average cost of the system itself is between £1,700 to £3,500

The cost of having it installed is where the real expense comes in. Most fitters will charge between £7,000 to £10,000 all in. 

The cost will depend on a few different factors. 

  • Size. Four-person systems are cheaper than 6-person systems. 
  • What’s already there. Old systems or septic tanks that need to be dismantled first will likely add to the cost. 
  • The land. If major works need to be done on the land before installation (like excavation or levelling) this can increase costs significantly. 

It sounds like a lot of money, but these systems are designed to last around 25 years. 

They’re also cheap to maintain. They’re simple systems and they’re extremely sturdy. You shouldn’t need to spend much more than £200 a year on maintenance and servicing. 

10. Using a home buying service to sell your Property (with as septic tank)

Selling a house is always stressful, but some situations are worse than others.

Needing to sell a house with a septic tank quickly is a big burden. 

It’s the kind of thing we spend precious hours out of our day trying to sort out, and hours at night worrying about it. 

If you’ve got a house you need to shift, using a traditional estate agent is rarely the quickest way. This is where home buying services come in.

Say for example you’re selling a house following a split, through probate after the death of a family member, or to release equity. 

You’re likely already dealing with considerable emotional stress. You may be spending your energy working through a divorce, looking after children, or acting as an executor of a will. 

A home-buying company simply takes away one major responsibility from your to-do list. 

Those selling a house in need of major works sometimes opt for house buying services too.

Perhaps the biggest benefit is that the service will buy a house no matter the condition. No quibbling, no demands, no long and drawn out negotiations. 

If you’re selling a house with septic tank issues, there’s no back and forth about who makes the repairs. 

The house buying service will simply take the property off your hands and get the cash into your bank account. This can sometimes be done within a week. 

You may never have to hear the words ‘septic tank’ again!

Resources for further help

We really hope this guide has helped you with selling a house with a septic tank. We hope you’ll feel much more informed and empowered to arrange your house sale with this guidance in mind. 

We’ll leave you with a handful of resources you can take action with today:

A full breakdown of the new septic tank legislation (Click Here).

Government General Binding Rules in full (Click Here).

Postcode search tool to check if you’re in a Groundwater Source Protection Zone (Click Here).

This handy guide breaking down the costs of different types of tanks, plants, and cesspits (bear in mind this is a company website featuring their pricing only. Always get quotes from 2-3 contractors before you go ahead (Click Here).

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To understand why going through us is both better and safer, instead of going directly to your home buying company of choice, click below.

We want to help out as many people as possible. That’s why we created this comprehensive article.

If you are looking to sell your property, call us on 0333 242 2814 or message us through the live chat.

Depending on your preference and circumstances, we’ll connect you for free with one of our strictly vetted, ethical partners. 

They will help you sell your property for the best offer you can realistically achieve.

They will take care of all of the legal processes and fees and you’ll get the cash straight into your bank account. 

With our partners you can achieve a very fast sale or a slower one if you’re not pressed on time.

Faster sales usually yield a lesser price but they save you time.

It all depends on your circumstances and preference.

Final thoughts

In this article, we explored selling a house with a septic tank and all of its nuances.

If your house is not connected to the sewerage system, you most likely have a septic tank on the grounds.

Septic tanks deal with all wastewater from the house. 

This includes water from the sinks, baths and showers, kitchens, and toilets.

And even though selling a house with a septic tank seems complicated, it doesn’t have to be. 

If you decide to use a quick home buying company, they will take care of everything and you can receive the money for your property in less than 7 days. 

If speed-of-sale is something that interests you, this might be your best option.

Of course, by choosing speed, you have to sacrifice a bit of your property’s selling price.

But that’s a very reasonable trade off for many people.

Therefore, if your house has a septic tank and you don’t have time to check if it’s working properly, troubleshoot and repair it, consider working with one of our strictly vetted house buying partners.

They will buy the house from you fast and you will won’t have to deal with any septic-tank-related issues, nor any other house-related issues at all.

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