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Heating oil explained

Maintaining and fixing problems

By Liz Ransome-Croker

Article 4 of 5

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Maintaining and fixing problems

Find out how to protect and maintain your heating oil tank, plus what your rights are if you're having problems with your heating oil supplier.

From preventing leaks and stopping heating oil from becoming sludgy in icy weather, to keeping your oil safe from thieves, we tell you all you need to know about maintaining and fixing your heating oil tank.

Follow our checks and advice to keep your heating oil safe and save you money in the long run. We've also got expert advice on what to do if you're having problems with your supplier. 

Heating oil tank checks

You should have your heating oil tank serviced once a year by a technician registered with Oftec (the Oil Firing Technical Association). You can visit the Oftec website to find one in your area. 

There are also some simple checks and precautions you can take yourself to ensure 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 (take a look at our page on heating oil tanks to find out more), isn't filled with large amounts of water, oil, rubbish or plants. 
  • 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 doesn't get into them.
  • Check 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. 

If your boiler's on its last legs, make sure you get a reliable replacement. Take a look at our oil boiler reviews to find a reliable model rated highly by customers and heating engineers.

Heating oil leaks

Oil is toxic and harmful to the environment, including animals, plants and water sources. It is against the law to cause pollution, so any defects found should be fixed immediately by a professional. 

In the case of oil escaping from the tank, you should call the Environment Agency's 24-hour incident hotline (0800 807060). 

It can cost thousands to clean up an oil spill, so it's advisable to 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.

Be aware that not all insurance policies cover oil leakage. Take a look at our guide to home insurance for more information, and to find which insurance companies are highly rated by its customers. 

All heating oil tanks should have the correct protection around them, such as a bund (secondary containment), according to regulation. The amount of protection varies across the UK and depending on where your tank is situated. 

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

Go to heating oil tanks to find out more about the types of heating oil tanks and changing heating systems.

Will heating oil go bad? 

If it gets into your tank, sludge or water can affect your heating oil by clogging pipework, damaging or corroding heating systems and reducing the efficiency of the oil. 

Water can get in if it's raining when you have a new oil delivery, or due to condensation. You should take precautions to ensure any damage is fixed and openings are closed, and your delivery driver should do the same when filling your tank. 

Sludge tends to build up in tanks where oil has been stored for a long period. 

To detect water or sludge, look for a darkened area at the bottom of the tank.

To detect either water or sludge, look for signs of a darkened area at the bottom of the tank, which may have been caused by erosion. 

You can also buy water-finding paste which you would need to attach to a long stick to put into the tank. The colour the paste turns will 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. 

Find out if you can cut your energy bill by installing a wood burning stove. See our guide to stove costs and savings.

Will heating oil freeze?

Heating oil won't technically freeze and become a solid lump. However, in very cold weather (usually minus 39 degrees), heating oil can ‘wax up’, which is where it forms crystals that stop it from flowing as easily.

There are two types of heating oil - gas oil and kerosene. The latter is less likely to become waxy. You can also buy additives to add to your oil that will help prevent crystals from forming. For 1,000 litres of heating oil, expect to pay around £15 for additives.

Buying heating oil in winter

Regularly check how much oil you have left to avoid suddenly running out in cold weather - particularly on those occasions when a supplier can't get to you, such as during heavy snow.

Order more oil before your supply gets less than a quarter full. To avoid risks and save money, order most of your oil in summer, then simply top up in early winter before the weather gets too bad. 

If you run out unexpectedly, contact your supplier. If it can't reach you with an oil delivery it may have small supplies you can collect from a depot, if you can get to it. 

Need a new car you can rely on? We reveal the best SUVs and 4x4s.

Heating oil theft

Heating oil is pricey, so it can be attractive to thieves. Adding locks or lockable valves if possible will 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, although in doing this you must ensure 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 is 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 is 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. 

For more information on cutting your costs, take a look at our guide to getting the best heating oil price

Heating oil supplier problems

Some heating oil customers have complained that suppliers have changed the price of a heating oil order between it being ordered and delivered. It's worth checking what the terms and conditions of your purchase are, 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.  

But if there is an issue with the oil, such as it being sludgy and unusable, you have the same consumer rights as you do most other goods and services, which is covered in law by the Consumer Rights Act. Our full guide to the Consumer Rights Act can help if you are experiencing problems with your heating oil order. 

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 it will be calculated as well as any additional payments.

But it's worth noting that 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.

Make sure your supplier has written confirmation of where your tank is and how to get to it. 

Boiler maintenance

As with your heating oil tank, your boiler should be serviced once a year by an Oftec-registered technician. 

You can find a trusted, local technician to repair or service a boiler in your area by using Which? Trusted Trader, and find out more about the best oil boiler brands rated by customers and heating engineers in our guide.