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Oil tank risks

Risks to you

If your oil leaks into the ground, local river, stream or lake it can be expensive. The lost oil can cost you hundreds of pounds, but the clean-up costs are regularly more than £20,000. If groundwater or drinking water is affected, these costs can quickly escalate to six figures, unless dealt with swiftly by specialists.


You will likely be without heating or hot water, and need to deal with significant damage to your home; not to mention the disruption to daily life whilst you sort it all out.


If you live above groundwater used for public water supply it is likely that some of your property will need to be dug up to find and remove the oil before it causes too much contamination. In the most serious cases, this can mean moving out of your home for a prolonged period whilst the works are underway.

It's also important to check that your home insurance covers you for this risk. You need to be covered for a 'gradual environmental spill' not just 'sudden, accidental loss'. Search for an insurance policy that covers you properly if your insurer doesn't.

Oil tank in poor condition


Checking your oil tank

You should be checking your oil tank every month and before you place an order and getting annual checks by a competent person usually at the same time as a boiler service.

What to look for

You should look for anything on or around your tank installation that could indicate a leak is likely to happen, or oil has been lost to the environment. You should:

  • make sure that the tank installation isn’t becoming over grown with vegetation that would hide the condition of the tank

  • check the tank base or supports for cracking or subsidence

  • ensure the tank has a working contents gauge; if this has a valve make sure it’s closed

  • check all visible pipework, valves and filters for damage and signs of leaks, such as dampness or staining, especially around joints

  • check vegetation around the tank for signs of die-back

  • check secondary containment (tank bunds) for liquid or rubbish

  • check that drip trays for remote fill pipes haven’t got any oil or water in them, check the waste oil information for how to dispose of any liquid

If you have a plastic tank you also need to check for:

  • whitening, cracking and splits in the plastic

  • bulging or deformation of the tank profile

If you have a metal tank you also need to check for:

  • signs of rust, pitting and blistering of paint

  • oil dampness on seams and welds


If you see anything you’re worried about or that’s changed since you last looked you should take advice from a qualified oil heating professional. A plastic oil tank can’t be repaired; if it’s starting to show signs that it’s deteriorating you are likely to need a replacement tank.

If your oil use suddenly increases unexpectedly, you should check your tank and pipework immediately for leaks. Tank monitoring devices are available that give early warning of a rapid drop in oil level.

If you are concerened about the quality of your oil tank, Portsmouth Water offer free inspections to homeowners in groundwater vulnerable areas. To find out more and if you're eligible please click here.

Environmental impact

Oil pollution can have a devastating effect on the water environment, it spreads over the surface in a thin layer that stops oxygen getting to the plants and animals that live in the water. Oil pollution:

  • harms animals and insects

  • prevents photosynthesis in plants

  • disrupts the food chain

  • takes a long time to recover

Wildfowl are particularly vulnerable, both through damage to the waterproofing of their plumage and through eating the oil as they preen. Mammals such as water voles may also be affected too.

In the ground and soil oils coat or kill the organisms which are necessary to maintain the environmental balance.

Human impact

Contamination can make water unsuitable for irrigation and damage how water treatment plants work.

Oil spills can make drinking water sources unfit for use and is very expensive to put right.

If oil is spilt near to a building the oil vapours could enter the building making it unsafe for habitation. This could mean the building becomes unusable until expensive restoration work is completed, or in extreme circumstances the building may need to be demolished. If this is your home or place of work this can be devastating.

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