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Heating oil explained

Heating oil tanks

By Sarah Ingrams

Article 3 of 3

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Heating oil tanks

Read our guide to heating oil tanks to understand about the different types, prices and sizes, plus how to maintain your oil tank and protect yourself against oil theft.

Heating oil tanks are made from fabricated steel or plastic and can be installed inside, outside or underground. 

Keeping your tank and system well maintained will keep them as efficient as possible, which helps to keep your costs down and reduce the risk of breakdown.

The oil in your tank is valuable, so it’s also important to protect it from theft as best you can.

Read on to find out all you need to know about heating oil tanks, including the types, essential measures to safeguard against leaks, and maintenance. Click on the links below to jump straight to the section you need:

If you're thinking of updating your heating system, see our oil boiler reviews to find out which have been rated the most reliable by customers and heating engineers.

Heating oil tanks: the essentials 

Made from either fabricated steel or plastic, heating oil tanks can be single-skinned, double-skinned (where the tank has two layers) or integrally bunded (a bund is a protective layer).

Integrally bunded tanks have one tank sitting within another. The outside tank houses the main tank's fittings and vents (see image gallery below). These tanks give better protection than double-skinned tanks, as there is more room between the two layers to prevent oil leaking externally.

Most single and double-skinned tanks need to have a bund built around them for protection, although this will depend on where you live and the position of your tank. The bund can hold 110% of the tank's contents.

Where can I buy a heating oil tank? 

Heating oil tanks are available online or through a local, independent company. Before you buy a tank, check that it's manufactured to Oftec standards. An Oftec-registered technician can help you choose the type of tank and where to put it so that it complies with location regulations (to limit environmental and fire risks) and building regulations, both of which vary across the UK.

You can visit the Oftec website to find one in your area, or contact the Environment Agency for further advice.

Heating oil tank prices 

Prices generally range from around £500 for a small single-skinned tank to more than £2,000 for a large integrally bunded one. Price will also depend on size, which can vary from around 1,000 to more than 3,500 litres (although these tend to be used commercially).

How much heating oil do I need? 

1,000 litres could last up to a year, but it depends on a number of factors, such as:

  • the size of your house
  • how long you have your heating on
  • whether your oil boiler is efficient.

Try to work out how much you're using by keeping tabs on your tank gauge over time. 

All heating oil tanks should have a gauge in one form or another to indicate how much oil is left in the tank. This may be on the tank, next to it, or displayed remotely. 

If your tank doesn't have one, you can buy one separately. They cost anything from £25 for a basic gauge, to more than £80 for a digital remote one. 

It's important to keep a close eye on your oil tank gauge so your supply doesn't get too low. Make sure you order more oil before it becomes less than a quarter full, especially in winter. 

It's worth noting that you should only fill your tank to around 80-90% of its capacity to avoid spillages. 

Don't pay more than you have to for heating oil. Read our expert advice on how to get the best price for heating oil.

How often should my oil tank be serviced? 

Get your tank inspected annually to ensure it's in good working order. Some manufacturers recommend six-monthly checks. A technician registered with the oil-firing industry trade association, Oftec, should carry out the service. Find an Oftec-registered technician here.

Inspections cost around £70-£100. If you've moved into a new property and ‘inherited’ your heating oil tank, it's worth arranging an inspection as soon as possible.

Steel tanks have an oil-resistant coating, which needs to be maintained to prolong the life of the tank. Check with the manufacturer to find out what maintenance is needed besides yearly servicing. 

You should also have your oil boiler serviced annually. Find a trusted local engineer using Which? Trusted Traders.

Oil tank checks you can do yourself 

Besides an annual service, there are simple checks and precautions you should take to make sure your tank is in a good condition:

  • Check for signs of damage, such as bulges, deep scratches, cracks, discolouration, rust or major dents.
  • Look out for any oil that has leaked out externally, particularly around pipes, valves and seams.
  • Make sure that any external protection, such as a bund (scroll up to find out more), isn't filled with large amounts of water, oil, rubbish or weeds.
  • Keep access to and around the tank clear, and don't allow plants to grow near it.
  • Make sure vents, gauges and access points are closed and protected so that rainwater, insects or dirt can't get into them.
  • Check that gauges and alarms are working correctly, and in particular the batteries. Consult the manufacturer for advice on how to do this.
  • Keep an oil-spill kit with drain blockers, leak-sealing putty and absorbent materials.
  • Make sure your tank is only filled to around 80-90% of its capacity to avoid overfilling, and ensure your tank has an overfill protection device or alarm.

What you should do if your heating oil tank leaks 

Oil is toxic and harmful to the environment, including animals, plants and water sources. It's against the law to cause pollution, so any defects found should be fixed immediately by a professional.
If oil is escaping from the tank, call the Environment Agency's 24-hour incident hotline (0800 807060).

It can cost thousands to clean up an oil spill, so you should get insurance that:

  • has a high enough liability limit to cover the cost of cleaning up your property or neighbouring land
  • covers the cost of replacing lost, leaked or stolen oil
  • covers environmental clean-up for accidental loss.

Not all insurance policies cover oil leakage. See our guide to home insurance for more information, and to find which insurance companies are highly rated by its customers.

If you need to change your current tank, it's important to get one that's manufactured to Oftec standards (OFS T100 for plastic tanks or OFS T200 for steel tanks).

Heating oil tank problems: sludge, water and cold weather 

If sludge or water get into your tank, they can clog up the pipework, damage your heating system and reduce the efficiency of the oil. Water might get in if it’s raining when your oil is delivered, or from condensation. Sludge tends to build up in tanks where oil has been stored for a long time.

Look for signs of a darkened area at the bottom of the tank; this can be caused by erosion due to sludge. You can also buy water-finding paste which changes colour to indicate whether water is present. 

A technician can remove water and sludge and clean your tank, as well as fixing whatever's causing the problem.

Even when it’s very cold in winter, heating oil doesn’t technically freeze into a solid lump. However, in very cold weather (usually -39°C), heating oil can ‘wax up’, which is where it forms crystals that stop it from flowing as easily. Kerosene is less likely to become waxy than gas oil, but you can buy additives to help prevent crystals forming. These cost around £15 per 1,000 litres of oil.

Heating oil theft 

Heating oil is pricey, so it can be attractive to thieves. Adding locks or lockable valves will help to prevent theft, and in some cases is a legal requirement. Your engineer or supplier can advise you on this.

It's also wise to shield your tank from the road so it isn't visible. However, in doing this you must ensure that access to it isn't restricted and it complies with guidelines. Ask an Oftec-registered technician for details.

You could also install motion-sensitive security lighting to alert you if there's a problem, or an alarm (costing around £80) that will react if the oil level drops suddenly – which is also useful for notifying you of an oil leak.

It's cheaper to order your heating oil in bulk, but some people prefer to order less and more often so that, if the oil is stolen, there is less to lose. One way to reduce the price when ordering a smaller amount is to join a heating oil club. Find out more about these in getting the best price for your heating oil.

Know your rights with heating oil suppliers 

Price changes: Some customers have complained that suppliers have changed the price of a heating oil order between order and delivery. Check the terms and conditions of your purchase, as some can specify that the contract isn't formed until the oil is dispatched.

If a contract allows for the price to be increased after it has been agreed, it should generally give you a right to cancel if the new price is too high.  

To reduce the risk of getting a nasty surprise when you receive your bill, always get a written confirmation of the order that includes the amount of oil you're ordering, the price and delivery timescales.

If you order over the phone, this is classed as a distance selling contract. So your supplier must give you certain information, such as the price agreed. Where this isn’t possible, it should show how the price will be calculated, as well as any additional payments.

But the cooling-off period under the Consumer Contracts Regulations distance selling regulation, where you can cancel within 14 days, doesn't apply to heating oil. Find out full details about distance selling rights and regulations in our full guide to the Consumer Contracts Regulations.

Problem with the oil: If the oil delivered is sludgy and unusable, you have the same consumer rights as you do for most other goods and services, which are covered in law by the Consumer Rights Act. Our full guide to the Consumer Rights Act can help if you're having problems with your heating oil order. 

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