What to Do if There’s Water in Your Oil Tank

Water in your heating oil tank isn’t always obvious until it causes a problem. It’s something you need to be vigilant about, as prevention is better (and cheaper) than cure! It’s no good finding that cheap home heating oil only to lose those savings on an expensive call-out! Remember, if there’s an extreme cold snap, water can freeze in the pipes, causing a blockage or even cracking them!


Where does the water actually come from?

Usually, water in an oil tank comes from either condensation or rainwater. The condensation can develop when there’s a big difference between the oil and the outside temperature. Rainwater can enter the tank in several ways:

  • The filling cap not being replaced properly, or being left off for too long;
  • faulty seals on the caps;
  • damage to the vents, and
  • cracks in the tank.

Making sure the tank cap is replaced properly is really easy, but if you think you have any of the other issues, you’ll need professional advice and help.

How can I tell if there’s water in the tank?

Water can be hard to detect because it tends to sink to the bottom of the tank. An easy way to detect it is to use a water-finding paste – this paste changes colour if it comes into contact with water. You’ll need a rod or stick long enough – a length of garden cane for example – and you apply the paste to it and place it in the tank so it touches the bottom. Leave it for as long as the instructions tell you, then examine the colour.

OK, I have water – what do I do?

If you’ve found water you’ll need to get rid of it ASAP, before it gets into your AGA or boiler. If your oil tank is metal it will probably have a sludge valve at the bottom, so you can open it and drain out the water (remember, water sinks in kerosene). If you have a plastic tank you may need to have the water removed by a hand pump, in which case you’ll need a qualified engineer.

The water that is removed will be contaminated with your oil, so it really mustn’t go down the drain or into any water body. If you remove the water yourself, contact your local council to find out how to dispose of it safely, as there’s probably a waste oil collection service or depot.

Once your tank is free of water, you should have the feed pipe flushed out, and you should also change your fuel filters, as they may have picked up some water as well.

How do I stop water getting into my tank?

There are also oil tank water soakers – these are placed at the bottom of the tank where they absorb water. They’re easy to install, but you need to insect them regularly and change them out several times a year. As with drained-off water, you need to dispose of the soakers in the right way.

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