Which Heating Oil Tank?

At the heart of any oil heating installation is an oil storage tank. When correctly installed and maintained, today’s oil tanks can provide many years of safe, secure and environmentally responsible fuel storage.

To bund or not to bund?

At above-ground, domestic oil storage installations, it is important to determine whether or not you require either a single skin or a bunded  oil tank. A bunded oil tank consists of a tank within a tank. The oil is stored in the inner tank, whilst the outer tank is designed to act as a containment area in the event of a spillage originating from the inner tank e.g. as the result of an overfill.

Bunded oil tanks are now a requirement at all new agricultural, commercial, industrial, institutional and most domestic installations too, including all domestic installations with an installed capacity of 2,500 litres or greater. To determine whether or not a bunded oil tank is required, an Environmental Risk Assessment should be undertaken at the proposed installation site by a competent person:

Environmental Risk Assessment – Above Ground Oil Tanks


  • Will the oil tank be positioned within 10 metres of a watercourse e.g. sea, lake, river, stream, drainage ditch etc?
  • Will the oil tank be located in a position whereby a spillage could run into an open drain or reach a loose fitting manhole cover?
  • Will the oil tank be situated within 50 metres of a well, borehole or spring?
  • Will the oil tank be positioned in such a manner whereby any spillage could pass over hard ground and enter a watercourse?
  • Will the oil tank be used for any purpose other than the storage of fuel for heating and / or cooking purposes at a private, domestic dwelling occupied by a single family?
  • Will the oil tank be situated in a position where the vent point is not visible from the fill point?
  • Will the total installed capacity be greater than 2,500 litres?
  • Will the oil tank be installed within a Groundwater Special Protection Zone 1 area?


  • Will the oil tank be installed in the Channel Islands or Isle of Man?
  • Will the oil tank be installed within an Area of Special Scientific Interest, a National Park or an Area of Outstanding Natural Beauty?

If the answer is ‘Yes’ to any of the above questions, or if you are unsure if any of the above factors apply – then a bunded oil tank must be installed.

Fitting a single skin oil tank where a bunded oil tank is legally required, is a criminal offence. All Risk Assessments should only be undertaken or confirmed by a suitably competent fuel tank installer e.g. an OFTEC Registered Technician.


Single Skin Oil Tanks

Even if a single skin oil tank will currently suffice, it should be noted that single skin oil tanks do not incorporate any form of inbuilt secondary containment. Therefore in the event of a spillage, a pollution incident will result and hence at any installation, serious consideration should be given to the installation of a bunded oil tank.

Which capacity?

The ideal capacity for any oil tank installation will depend upon three factors;

  • The size (output) of the boiler
  • How often the boiler is used
  • The size of the house

As a rule of thumb, we would suggest making an allowance of 500 litres per bedroom – subject to a minimum heating oil tank capacity of 650 litres. Therefore at a three bedroom house, we’d suggest the optimum tank will be around 1,500 litres or greater; at a 4 bedroom tank we’d suggest a tank capacity of c.2,000 litres or greater; and at a 5 bedroom house, we’d suggest a tank capacity of c.2,500 litres or greater. Subject to minimum delivery volumes, you can of course opt for a smaller tank – but this will require refueling more often than a larger tank.

Your boiler manufacturer or fuel tank installer can also provide guidance as to optimum oil tank capacity and likely fuel consumption. Additionally, it is worth giving serious consideration to buying a slightly larger oil tank than may be required. This allows you to stock up with heating oil when prices are lower and extends the period between refills.

Cooking with oil?

Oil is a popular cooking fuel in non-mains gas areas throughout the United Kingdom. At many installations, an oil fired boiler and cooker will often be fed from the same oil tank – assuming that they consume the same fuel type. Your fuel supplier or cooker manufacturer can advise if required.However, where a separate oil tank is required to supply fuel to the cooker, or where the primary boiler burns a fuel other than oil, we would recommend consideration is given to a tank with a capacity between 650 litres – 1,000 litres.If you require further advice, please do not hesitate to contact us or e-mail TankDepot.co.uk’s Technical Support Team directly for further assistance.
IMPORTANT INFORMATION Every effort is made to keep this area of the site up to date. However, TankDepot.co.uk cannot be held liable for errors and omissions. Legal compliance is the user’s responsibility. If you have concerns over compliance, you must seek professional advice, or contact your or local building standards or environmental authority. Additionally, TankDepot.co.uk recommends that all storage tanks should be installed only by a competent person e.g. an installer registered with The Oil Firing Technical Association (OFTEC). Please note that TankDepot.co.uk will not be responsible for any installation which is non-compliant with prevailing statutory requirements.