The Danish Soil Contamination Act (jordforureningsloven) has special rules for oil tanks of under 6.000 litres where at least half of the floor area the tank heats is used as living space. A tank like this is usually called a villaolietank (domestic oil tank). That classification determines which rules apply to the particular oil tank in your garden, and both parties to a sale have a responsibility for it. The seller must be able to document that the tank is legal and that any decommissioning (sløjfning) has been carried out correctly. If the tank is in use at handover, it is, as a rule, the buyer who, as the new owner, may be served an order by the municipality if pollution is found. Who ultimately bears the cost is something buyer and seller can only agree between themselves.
This article only covers tanks under 6.000 litres. Larger tanks and tanks for biodiesel follow other rules and are only mentioned briefly. If you are unsure which category your tank belongs to, your municipality can tell you.
The aim is to give you an accurate, source-based overview of the rules, so you know which documents to find, who is liable for pollution and what the sale should include. The article covers the types of tank and their characteristics, registration in BBR (the Danish building register) and the property data report (ejendomsdatarapport), correct decommissioning, decommissioning deadlines, the tank certificate (tankattest), liability for pollution, insurance and checklists for both buyer and seller.
The article is based on the Soil Contamination Act, the Executive Order on Oil Tanks (olietankbekendtgørelsen) and the municipalities’ guidance. It contains no recommendation of particular tanks and no ruling on specific cases, as that does not belong in a general overview. If you have a case that needs a decision, go to your municipality and the right professional.
Which oil tanks are covered by the rules
Three things determine which rules apply to an oil tank in the garden: its size, its contents and its labelling. First, find out which category your tank falls into. The table below compares the three categories.
| Tank category | Rules that apply | Decommissioning |
|---|---|---|
| Domestic oil tank (under 6.000 litres) | Sections 48 and 49 of the Soil Contamination Act on orders and compulsory insurance, plus the Executive Order on Oil Tanks, which regulates installation, operation and decommissioning | Must be decommissioned no later than the deadline the Executive Order on Oil Tanks sets for the tank type |
| Tank of 6.000 litres or more | Requirements for self-monitoring, inspection and leak testing | No general decommissioning deadline under the same rules |
| Oil tank for biodiesel and other bio-based heating fuels | Not covered by the Executive Order on Oil Tanks | Special permission must be sought from the municipality |
Once a tank reaches 6.000 litres, a different set of rules applies. Instead of a decommissioning deadline, the tank is subject to ongoing checks through self-monitoring, inspection and leak testing. Bear this in mind if your tank is close to the limit, or if you are unsure what size of tank is actually in your garden.
Biodiesel and other bio-based heating fuels fall entirely outside the Executive Order on Oil Tanks. There is no standard set of rules to fall back on here. Instead, you must apply to the municipality for special permission, whatever the size of the tank.
Labelling and location
A new oil tank must be type-approved, and CE-marked tanks made to a harmonised standard count as type-approved. A tank that is type-approved in Denmark has a rating plate showing the manufacturer’s name, the tank type and capacity, the serial number and year of manufacture, and the type-approval number. The rating plate makes it possible to work out which requirements and deadlines apply to your particular tank, and it is usually the first thing a municipality or a buyer looks for.
The labelling also tells you where the tank may be placed. The tank certificate states whether the tank is approved for indoor or outdoor installation, and on tanks from 2000 onwards you can also see it in the type-approval number: if there is a 1 in the second-to-last position, the tank is for indoor installation, and if there is a 2, it is for outdoor installation. An indoor tank must stand within the outer walls of a heated building.
A tank for indoor installation that has ended up in an unheated shed or under a carport is therefore, as a rule, not where it should be. However, tanks from before 2000 may stand indoors in an unheated room. A tank for outdoor installation, on the other hand, can stand outside. If you are unsure what the labelling on your tank means in practice, your municipality can tell you which requirements apply in your situation.
Registration in BBR and the property data report
The public registers are the first place to look if you want to know whether there has been an oil tank on the plot. Both new tanks and any decommissioning must be reported to the municipality, which updates BBR once it has received the notification. Keep the receipt for the notification and the updated BBR notice. They are part of the documentation for the tank that a sale can rest on.
The notification deadlines differ depending on whether it is a new tank or a decommissioning. A new oil tank must be reported no later than 14 days before installation begins. If a tank is permanently taken out of use, it must be decommissioned, and the municipality must be notified no later than 4 weeks after the decommissioning has taken place. The two deadlines fall at very different points in the process, so keep them apart when you read through older papers.
Where to find the information
Information about an oil tank is kept in several places, and they do not necessarily cover the same things. You will find it in BBR, in the property data report and in the municipality’s building case archive, which in many municipalities is called weblager. You can see the BBR details by searching for the address on bbr.dk.
The weblager is often where the details are kept. It holds tank certificates, notification and decommissioning forms, and maps showing where on the plot the tank has been. This material can settle whether a decommissioning was carried out according to the rules, so take the time to go through it if you want a reliable picture of the tank’s history.
Registration only goes back to 1970
The duty to report oil tanks came with the first Executive Order on Oil Tanks in 1970 and at first applied only to underground tanks. Above-ground tanks did not have to be reported until 1980, and there are examples of incomplete registration. So an empty field in BBR is not proof that there has never been a tank on the plot.
If the tank is removed from the property, you may not be able to see its history in BBR. The information is usually still kept in the weblager. If you need to document that a tank has been there and was decommissioned correctly, you need the weblager and the building case archive, not just the current BBR status. If you are unsure what is registered for your property, your municipality can tell you.
Correct decommissioning: emptying, cleaning, blanking off or digging up
Correct decommissioning requires the tank to be completely emptied of oil and sludge. The tank must then either be removed or blanked off. The work must always follow the Executive Order on Oil Tanks, and it is a good idea to have an authorised plumber carry it out. If the tank is left in place, the steps are as follows:
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Empty the tank completely of oil and sludge.
Remove the above-ground part of the fill and vent pipes.
Blank off the pipes so the tank cannot be filled again.
When emptying the tank, it is a good idea to suck out the remaining product and then flush it twice with water, sucking it out after each flush. This gives a cleaner tank with less residue.
The two methods
There are two ways to decommission an oil tank. One is to dig the tank up. The other is to leave the tank in place, remove the above-ground part of the fill and vent pipes and blank off the pipes so that the tank cannot be filled with oil again. Whichever method you use, both the tank and the pipes must be completely emptied of oil and sludge. What matters is that the work is done according to the regulations.
The blanking off should be done by an authorised plumber, a master smith or an oil heating engineer. They can vouch that the tank has been sealed correctly so that it cannot be filled.
Digging up underground tanks is not a legal requirement. It is often recommended because it gives the clearest picture of whether there is pollution around the tank. If you choose to leave the tank in place, it must be emptied and blanked off according to the regulations. Moving an above-ground tank is allowed as long as the installation requirements are met and the decommissioning deadline has not passed.
Getting the documentation in place
Once the work is done, the municipality must be told that the tank has been decommissioned and how it was done. Ask the company that emptied the tank for written documentation of the emptying, and send a copy to the municipality. The documentation shows that the decommissioned oil tank has been handled correctly. Keep it with the property’s other documents.
If you come across pollution during the decommissioning, contact the municipality immediately. You cannot wait until the work is finished, and the municipality can tell you what needs to happen.
Decommissioning deadlines for different tank types and materials
When an oil tank has to be decommissioned depends on its material, construction and type approval, and on whether the tank is above or below ground. There is no single date that applies to all tanks. The deadline is calculated from the year of manufacture, i.e. the year the tank was made, and counted as a number of years after that.
The table below shows the main decommissioning deadlines for oil tanks under 6.000 litres, as set out in sections 44 and 45 of the Executive Order on Oil Tanks. It is not exhaustive. Above-ground steel tanks type-approved as double-walled must be decommissioned no later than 40 years after the year of manufacture, and other above-ground steel tanks not listed in the table no later than 30 years after. Underground steel tanks with a type-approved external coating other than glass-fibre-reinforced polyester must be decommissioned no later than 50 years after the year of manufacture.
| Tank type | Deadline (years after the year of manufacture) |
|---|---|
| Above-ground type-approved steel tank with internal corrosion protection | 40 years after the year of manufacture |
| Above-ground single-walled plastic tank | 25 years after the year of manufacture |
| Above-ground type-approved double-walled plastic tank | 40 years after the year of manufacture |
| Above-ground tank made of a material other than steel or plastic | 25 years after the year of manufacture |
| Underground type-approved steel tank with internal corrosion protection and an external glass-fibre-reinforced polyester coating | 50 years after the year of manufacture |
| Underground type-approved steel tank without internal corrosion protection, but with an external glass-fibre-reinforced polyester coating | 40 years after the year of manufacture |
| Underground plastic tank | 45 years after the year of manufacture |
An underground steel tank with both internal corrosion protection and an external glass-fibre-reinforced polyester coating has one of the longest deadlines: 50 years. An above-ground single-walled plastic tank, on the other hand, must be decommissioned no later than 25 years after the year of manufacture.
Special cases where the deadline has already passed
Some tanks do not have an ordinary deadline. Underground plastic tanks with an unknown year of manufacture should have been decommissioned by 31 March 2015 at the latest. If a tank like that is still in the ground, it is long overdue.
Spherical underground polyethylene tanks from AJVA-PLAST A/S must be decommissioned no later than 20 years after they were buried.
If the year of manufacture can neither be found nor determined, the tank must be decommissioned, and in practice that means immediately. Without the year, there is no deadline to calculate, which is why it is important to find it.
Where to find the year of manufacture
The rating plate on the tank shows the year of manufacture and also tells you what type of tank you have. That information is the basis for the whole calculation of the decommissioning deadline, so look for the plate first.
Many old above-ground tanks have no rating plate, because one was not required when they were installed. In those cases, the year may be given on the tank certificate instead. The certificate is often the only place where the year of manufacture has been preserved.
If you can find neither a rating plate nor a certificate, you have a tank with no known year of manufacture. In that case, the rule is that it must be decommissioned immediately. If you are unsure what applies to your tank, the municipality can tell you.
The tank certificate and why it matters
The tank certificate is the manufacturer’s document for the tank. Among other things, it contains a declaration that the tank type is type-approved in Denmark, the type-approval number, the serial number and year of manufacture, and the instructions for use and siting, including whether the tank may stand outdoors. For CE-marked tanks, the equivalent document is called a declaration of performance.
The owner must always keep a copy of the certificate. It documents that the tank is legal and has been installed in line with the applicable requirements. Without the certificate, the tank’s status rests on assumptions.
Never buy a tank without a certificate
Never buy a used or new oil tank without a tank certificate. The certificate is needed to document that the tank is legal. Without it, you can prove neither that the tank is type-approved for heating oil nor that it is allowed to stand where it stands. This applies whether the tank is brand new or has stood in someone else’s garden for years.
Reusing above-ground tanks
If you want to reuse an above-ground tank, the requirements depend on the year of manufacture. If the tank is from 2000 or later, it must be type-approved and the tank certificate must be available. Above-ground tanks from before 2000 can be reused if they still have the original rating plate showing the manufacturer’s name, tank type and capacity, and the serial number and year of manufacture. Underground tanks must not be moved.
For the older tanks, it is the rating plate that carries the documentation, because the certificate did not always come with the tank in those days. If the tank has neither a certificate nor a rating plate, you have no documentation of its type and age. That becomes a problem when the tank has to be assessed in connection with a sale.
The certificate must be sent to the municipality
The tank certificate must also be sent to the municipality. The municipality must have a copy immediately after the tank has been installed, and some municipalities ask for it as early as the notification stage. When you notify the municipality of a new tank, you must also describe the installation and enclose a sketch showing where the tank will stand.
The certificate follows the tank all the way: from the manufacturer to you, on to the municipality when the tank is installed, and finally into the papers that document the tank’s history. If you are unsure what needs to be sent in, the municipality can tell you.
Liability for oil tank pollution and the Soil Contamination Act
Under section 48 of the Danish Soil Contamination Act (jordforureningsloven), liability for pollution from an oil tank lies with whoever owns the tank at the time the pollution is discovered. This also applies to pollution that arose before you became the owner. The municipality can order an investigation and a clean-up regardless of how the pollution occurred, and as a rule the costs are covered by the insurance that the tank owner must have under section 49.
If you buy a property with an oil tank in use, as a rule it is you, as the new tank owner, who may receive an order from the municipality if pollution is discovered. No clause in the purchase agreement (købsaftale) can change that. You and the seller can only agree between yourselves which of you ultimately pays. You therefore cannot count on an old leak that you only discover after the handover automatically becoming the previous owner’s responsibility. That is one of the reasons why the documentation for the tank must be in place before the papers are signed.
When the insurance obligation has ended
Once the obligation to have domestic oil tank insurance has ended, the municipality can no longer issue orders under section 48 of the Soil Contamination Act. From then on, the Act’s other rules and the Environmental Protection Act apply, and under them the municipality can, as a rule, only issue orders to whoever caused the pollution.
The difference matters in practice. As long as section 48 can be used, the current owner can be served with an order, regardless of when the pollution occurred. Once the obligation has ended, the focus shifts back to whoever actually caused the pollution. In practice, it can be hard to point to anyone if the tank is old and has had many owners. If you are unsure which set of rules applies in your case, the municipality can tell you.
The duty to report pollution
If you discover pollution from an oil tank, as the owner you are obliged to report it to the supervisory authority. The duty does not disappear just because the pollution is old or comes from a previous owner. It stays with you: you must also disclose any pollution that has been found when you later sell the property. That disclosure often leads to a price reduction, because the buyer now knows the risk and can take it into account.
If the tank suddenly springs a leak, or there is a major spill of oil or petrol, a stricter rule applies. The incident must be contained immediately and reported by calling 1-1-2. It cannot wait until office hours or the next day, and it is not the same as the ordinary report to the municipality.
Disclaimers of liability and the buyer’s claims
An order from the municipality cannot be signed away, but buyer and seller can divide liability between them in the purchase agreement. The seller can disclaim liability for pollution towards the buyer, but the clause must be clearly worded. There must be no doubt that the buyer bears the risk of soil contamination. Unclear wording may end up being read in the buyer’s favour.
If the seller was unaware of hidden pollution and acted in good faith, the buyer is, as a rule, entitled to a proportionate reduction in the price and, more rarely, to damages. The seller’s lack of knowledge does not necessarily mean there is nothing to settle financially with the buyer.
There is also a time element, as claims against a previous owner can become time-barred. When the limitation period starts to run, and how that affects your case, is for a lawyer specialising in property law to assess.
Insurance against oil pollution and its conditions
- In March 2000, the oil industry set up an insurance scheme for tank owners. The scheme covers the clean-up of soil contamination caused by oil leaking from a tank installation. It applies to owners of oil tanks under 6.000 litres used for heating, in other words the domestic oil tanks this article is about. The insurance is provided by Topdanmark, and in practice most tank owners are covered by it.
The scheme links the clean-up to an order. The municipality must issue an order under section 48 of the Soil Contamination Act before the insurance scheme is obliged to open a case and cover clean-up costs. Once the order is in place, and the other conditions are met, the insurance covers the costs the authorities have imposed on you. These can include technical investigations and the actual clean-up of the contaminated soil.
When you are insured
To be covered, at least 50% of the floor area heated with oil from the tank must be used as living space. That is the basic condition, and it decides whether your tank falls under the scheme.
If your heating oil is delivered by one of the oil companies taking part in Drivkraft Danmark’s insurance scheme, or by a supplier that gets its oil from one of them, you automatically have the liability insurance. You pay the premium through your heating oil, as part of the oil price. So you do not need to take out any insurance yourself if you buy oil through one of the companies in the scheme.
The deadlines to keep an eye on
The cover is not unlimited in time. The insurance only covers up to 6 months after the tank has been taken out of use. Once you take the tank out of service, the clock starts ticking, and after the deadline there is no longer any cover.
There is also a reporting deadline. The pollution must be discovered while the cover is still running, and the insurance company must be told straight away when you discover pollution or suspect it. If the pollution has not been reported within 6 months of the cover ending, the obligation to pay compensation lapses. So if you discover pollution shortly before the cover ends, you need to act quickly.
Cover requires a legal installation
Cover requires the installation to be legal under the Executive Order on Oil Tanks (olietankbekendtgørelsen). The requirements for the tank, pipework and operation follow from the executive order, and as the tank owner it is your responsibility to make sure the installation complies with the rules.
If the tank is illegal or should have been decommissioned, the insurance company is not obliged to cover the soil contamination. An old installation whose decommissioning deadline passed long ago may therefore be left without the cover the owner assumed was there. That is why you should take the earlier sections on deadlines and labelling seriously when you assess your own risk.
The municipality can tell you whether your tank meets the requirements and what, if anything, needs to be done before an insurance claim can be considered.
The sale: checklists for buyer and seller
On a change of ownership, the sale can be made conditional on an expert inspecting the oil-fired heating system, the tank and the pipework with no issues found. Write precise conditions into the purchase agreement on legality, correct decommissioning and the absence of pollution, including the option to pull out if pollution is discovered.
Buyer’s checklist
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Find out whether there is, or has been, an oil tank on the plot and, if so, when it was decommissioned.
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Obtain the tank certificate and the documentation for any decommissioning, so that the tank’s type, age and history can be documented.
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Check that the decommissioning was carried out according to the regulations and that it was reported to the municipality.
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Check the BBR registration and compare it with the information in the property data report.
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Consider a preliminary environmental investigation, with boreholes around the spot where the tank has stood or been buried, before the sale goes through. It typically costs 15.000-40.000 kr. and can give some, but not complete, certainty about whether there is pollution.
Seller’s checklist
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Dig out the tank certificate and the documentation for any decommissioning, so they can be put on the table.
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Make sure the decommissioning has been reported to the municipality, together with a map on which the tank’s location is marked. If the notification has not been sent, a decommissioning form must be submitted.
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Disclose any pollution that has been found, as the duty to disclose follows you to any later sale.
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Have an expert check the tank’s type, age, location and pipe connections against the Executive Order on Oil Tanks.
Be aware of what happens if the documentation is not in order. If the tank was dug up without environmental supervision, soil samples and a technical environmental report from an environmental consultant, there is still no documentation of the contamination status when the property is bought and sold. Missing documentation can create uncertainty and, at worst, financial problems later on, when there is a change of ownership, an insurance claim or an enquiry from the municipality.
Banks and mortgage lenders also assess the risk. Where pollution has been found or the site is mapped as contaminated, lending may be restricted or refused altogether. That affects both parties to the sale.
A decommissioned oil tank is not always a risk. If it was decommissioned according to the rules and documented as having had no leaks, the risk may be small. Without an investigation, no one can give a definitive guarantee, which is why the paperwork matters so much. If you have a specific case, take it to the municipality and the right professional to have it assessed.
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