Expert advice on replacing an oil tank

How to know when to replace your oil tank?

We recommend that you have your oil tank inspected by one of our qualified OFTEC engineers if any of the following apply:


  • Oil Tank and pipework has not had an annual inspection;
  • Signs of corrosion or degradation is observed. This includes: oil staining, rust, discolouration, or cracks on the surface;
  • The oil tank has been damaged;
  • You can see signs of distortion or bulging;
  • Your oil tank is overgrown;
  • Any changes in the oil tank’s supporting structure or base;
  • Any signs of oil staining on the tank, supports or surrounding ground;
  • The level gauge is not working correctly;
  • Your oil tank is over 20yrs old.

How close to my house can I have my Oil Tank?

An oil tank has to be a minimum of 1.8 metres away from any part of a building or construction that isn’t fire resistant, such as doors, windows, eves, fences and cladding.

What rules and regulations should be followed when installing an Oil Tank?

Oil storage tank installations need to comply with regional Building Regulations. In England and Wales, OFTEC registered technicians can self-certify their own work without involving Local Authority Building Control. If you choose to use someone who isn’t registered with a ‘Competent Person’ scheme like OFTEC, then you will have to obtain a Building Control Notice.

Under oil tank building regulations for England and Wales, if the oil storage tank’s capacity is:

Over 2500 litres – it must have secondary containment (bunding).

Up to 2500 litres – it may need secondary containment (bunding) depending on the outcome of an individual site pollution risk assessment.

However, oil tanks with less than 2500 litre capacity must be bunded if the tank is:

  • Within 10 metres of controlled water
  • Located where spillage could run into an open drain or to a loose manhole cove
  • Within 50 metres of a borehole or spring
  • Over hard ground or hard surfaced ground that could enable spillage run-off to reach controlled water
  • Located in a position where the vent pipe outlet is not visible from the fill point
  • Supplying heating oil to a building other than a single family dwelling.

We would also recommend that you refer to OFTEC for more detailed guidelines and regulations regarding fuel and also see the UK Oil Tank Storage & Building Regulations.  

Do you have water in the fuel tank?

Condensation and leaks can occur in most Heating Oil tanks, allowing water to collect and build up over time. The presence of water can contaminate your fuel which can lead to a central heating boiler, or aga, failure. Your annual boiler service should include a tank inspection with a water dip made. If water is found your engineer will be able to remove the water, using something like a Tank Sponge which contains super absorbent polymers that remove water from the tank.

Average life of an oil tank?

OFTEC suggest a typical oil tank can have an expected working life of twenty years. This can increase with good maintenance, but might decrease with neglect.


A guide to preventing oil leaks




A guide to checking the level of heating oil in your storage tank?

Avoid running out of heating oil, causing costly damage to your boiler, and the need for an emergency delivery.

Set a regular day to check

However you choose to monitor your heating oil, it is a good idea to set a regular day to check your tank's oil level.

Whether you have a fuel gauge or not, popping a reminder in your phone or marking a specific day on your calendar can make all the difference and gets you into a routine.

And please do remember to check that your gauge is in working order. If it hasn't moved in a month and you know you've been using your heating there's a good chance it's not recording the level correctly.

Get to know your fuel oil tank

It may sound obvious but it’s helpful to know your starting point. If you’re unsure of the size of your tank and its capacity you should find a label on the tank that tells you. On more recent tanks, it may be on the front or side.

To measure, some tanks have simple float gauges or sight level tubes that allow you to keep an eye on your oil level. Make sure you turn the sight gauge lever when you check the level. It should be left in the off position to minimise the chance of leaks.

When your gauge indicates that the tank is still about one quarter full, it is a wise time to order. The winter months are the busiest time for fuel oil companies so ordering in plenty of time will avoid leaving it too late.

If you have a digital monitor

If your tank has a digital monitor that plugs into an electric socket inside the house, such as an Apollo or Watchman, ordering when the digit reaches 1 or 2 (1 or 2 bars) is usually the ideal time.

Most systems are designed to flash at either Level 1 or Level 2. When the monitor first starts flashing at these levels, there’s no need to panic or turn off your heating  as you have oil left in the tank - the flashing is merely a visible reminder to place your order.

A correctly set up tank should never have the sensors placed on the bottom of the tank so even when the monitor registers zero or zero bars there will still be approximately 10% of fuel left in the tank.

Can't beat a dipstick

If your tank has no gauging system, or you want to double-check the accuracy of your gauge, the best and most basic method is to measure and monitor how much oil you have with a dipstick by dipping the tank.

To avoid contamination, make sure you use a clean dipstick and that it is used solely for your oil tank.

To measure your tank manually Mister C says; take the cap off the top of the tank, which is where the fuel goes in, and put the dipstick right down to the bottom of the tank. When the stick is withdrawn, the oil will leave a mark on the stick consistent with the level of oil. When your tank level gets down to around the last 12 inches (approx. 30cm), we recommend it’s time to order your fuel.

What is a Watchman?

A Watchman is an automated oil monitoring device which is fitted in your home heating oil tank and sends a radio signal to a digital readout in your house. It allows you to easily monitor the oil levels in your tank and prevent run outs. Watchmans have replaced sight tubes on many domestic heating oil tanks over the last few years.

If the receiver detects a low battery a warning message is displayed on the unit in the home. It shows the oil level in the tank plus a constantly flashing warning triangle.

The lithium battery fitted to your Watchman will have a long service life, but it will eventually become exhausted and will need replacing. The battery model required is: VARTA CR2430, and they are available locally from good photographic shops or chemists or can be purchased online.

How to replace a watchman battery

9 Steps to replacing the battery:

  1. Switch off your Watchman display in the house
  2. Remove transmitter from tank
  3. Take transmitter indoors, into a clean dry environment
  4. Using a cross point screwdriver, undo the four screws, located under the main body of transmitter
  5. Remove the top cover, Flip out battery, Clip in new battery, Re-fit cover
  6. Evenly tighten all four screws - do not over tighten
  7. Replace transmitter on the tank
  8. Switch on your Watchman display in the house
  9. Wait 5 minutes for the oil level to refresh

Other possible Watchman error messages:

F = Full

Red Light Flashing with no level = No Signal

Red Flashing Light = Tank is low on fuel

Fluid Level Low & “BAT LOW” = New power tube needed

C = Connection fault replacement needed

Further information can be found here. Watchman Ultrasonic Installation Instructions

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