Single skin or bunded oil tank?

Choosing an oil tank

Choosing an oil tank can be tricky as there are many shapes, sizes and capacities to choose from. However the most important decision should be made at the outset, which is whether you need to install a single skin or bunded oil tank.  In commercial installations all oil storage tanks above 200 litres in capacity must be bunded. In domestic installations the regulations are more complicated and can vary from region to region, for example it is now illegal to install a heating oil tank without bunding in Wales. Oil tank installations are classed as notifiable works by Building Regulations and must be installed to the correct standards and therefore if you are planning on installing a single skin tank it is important to check with the Building Control department of your local Council, that the building regulations in your region do not require mandatory bunding. Obviously the safest way to achieve compliance (as well as safe and secure oil storage) would be to install a bunded tank. 

Bunding or secondary containment as it’s sometimes called can be achieved in a couple of ways. The first is a single skin tank which is situated in an open bund which is constructed from masonry and then sealed with an oil proof render. The bund must hold 110% of the primary tanks capacity. The disadvantages of this system are that the bund can fill up with rainwater and leaves etc. and therefore requires ongoing maintenance and if the water becomes contaminated with even a few drops of oil it will need to be tankered away as contaminated waste, which is a costly exercise. The second option is an integrally bunded tank which is effectively a tank within a tank; this usually results in a sealed bund.

Single Skin Tanks

Generally to install a single skin tank the following conditions need to be met:

• The capacity of the oil tank must be less than 2500 litres
• The tank must not be with 10m of controlled water (this includes watercourses such as rivers, streams, ditches and also septic)
• The tank must not be located where a spillage could run into an open drain or loose fitting manhole cover (this includes sink wastes and domestic drainage systems)
• The tank must not be located within 50m of a well (even disused), borehole or spring.
• The Tank must not be located over hard ground that could enable spillage run off to reach controlled water (so if the tank was located at the top of a concreted driveway and it failed could the oil travel down the drive to the storm water drain at the bottom of it?)
• The tank isn’t located in a position where the vent pipe is not visible from the fill point (this is for instance where the tanker connects onto a fill pipe at the front of the property and the tank is fitted at the rear)
• The tank doesn’t supply heating oil to a building other than a single family dwelling (e.g. office or other commercial property, multiple occupancy buildings)
• The tank isn’t located within a Ground Source Protection Zone 1 (this can be checked by visiting the Environment Agencies website)
• The tank is not in an area where regional regulations require mandatory bunding – for example Wales.
• There are no other potential environmental hazards
• Your home insurance policy doesn’t require the tank to be bunded

If you are confident that all the above conditions can be satisfied a single skin tank can be installed, but it is also worth checking with your neighbours that they do not have well in their garden or a loose fitting manhole cover on the other side of the fence by your oil tank.

As well as the actual regulations, it’s also worth considering how you would feel if your tank leaked and polluted your neighbour’s garden or the village pond?

Bunded tanks

Bunded tanks are the safest way to store oil, giving them many advantages, some of which are:

• A longer manufacturer’s warranty for extra peace of mind – most single skin tanks have 2 years, whilst bunded plastic tanks have 10 years.
• If a tank fails, the oil can be recovered from the bund and reused.
• Improved security as they usually have a lockable outer lid.
• Less chance of water ingress or condensation gaining access into the inner tank as it’s protected by the bund.
• Bunding can prevent expensive (and inconvenient) insurance claims for oil spill remediation

Without doubt, the safest and most compliant way to store oil is in a bunded oil storage tank and this is probably why integrally bunded tanks are the most popular choice for home owner who wants to store their oil responsibly and to protect their liquid assets.