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Dealing with Water in Your Heating Oil Tank

January 20, 2014 | Heating Oil Tanks

It may not be obvious that you have water in your heating oil tank until you have a problem with your boiler or Aga. It is something you need to keep an eye on and try to prevent if possible to avoid expensive call outs.

In extreme weather, it is possible that the water in your tank can freeze causing a blockage in the supply pipe.

Where Does the Water in my Oil Tank Come From?

The two main sources of water in your oil tank will come from condensation or rainwater. Condensation can build up on the walls of the tank when there is a temperature difference between the tank and its contents and the outside temperature. Rainwater can enter your tank for a number of reasons including:

  • The filler cap being left off or not closed properly.
  • Faulty seals.
  • Damaged vents.
  • Cracks or splits in the tank.

Whilst making sure the filler cap is closed correctly is relatively simple, if you have one of the other problems you will need to seek professional advice from an OFTEC registered engineer.

How do I Know if I Have Water in my Heating Oil Tank?

Water in you heating oil tank can be difficult to detect visually because the water will sink to the bottom of the tank. The easiest way to detect it is to buy some water finding paste. This will change colour if water is detected in your tank. Water detecting paste is applied to a stick or rod that is long enough to touch the bottom of your tank (a clean garden cane can be a good solution). The stick is placed into the tank so that it touches the bottom of the tank. You may need to leave it for a couple of minutes (check the manufacturer’s instructions) and then withdraw the stick carefully. If there is water present, the water finding paste will have changed colour.

How to Remove Water from Your Oil Tank

Once you have tested your tank and have found water, it is really important to remove it as soon as possible so that it doesn’t get into your boiler or Aga. If you have a metal heating oil tank you may find you have a sludge valve at the bottom of the tank which will allow you to drain off the water. If you have a plastic tank, you will need to have the water pumped out with a hand pump. This will need an OFTEC registered engineer.

You should also take care when disposing the water that is extracted as it will be contaminated with heating oil. You should NOT under any circumstances put it down the drain. Take it to a local authority waste disposal site which should have a waste oil collection tank. If you aren’t sure where this is, contact your local council for advice.

You may need to have the boiler feed pipe flushed and the fuel filters changed once the water has been removed.

Our heating oil tank water removal kit is the perfect solution to this issue. It includes water finding paste and a water absorbent tank sponge to soak up the water and remove it.

How do I Prevent Water Building up in my Tank?

The most obvious way to prevent water entering your tank is to make sure it is in good condition. Have it inspected annually by an OFTEC registered engineer and visually inspect it on a regular basis. See our tips on oil tank inspection.

To prevent condensation causing a problem in your oil tank, you can purchase oil tank water soakers that sit at the bottom of the tank and absorb the water. They are easily installed but they do need to be inspected regularly and changed every few months (depending on the manufacturer). As with contaminated water, the tank water soaker will also have to be disposed of correctly to avoid contamination.

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  1. This is some really good information about heating oil tanks. I had no idea that water can build up in the tank. It seems like you want to make sure that it does build up. I wonder if making sure that your oil levels don’t get too low will help prevent that.

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