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Trusted by over 500,000 customers for 20+ years
Order online or call
01480 775454
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Trusted by over 500,000 customers for 20+ years
Written by
Jenna Culy
on 06 Jun 2022
and updated on
12 May 2026
Categorised in
Tips and Advice
Very hot or wet weather can lead to water contamination in your heating oil tank. Heavy rain, condensation, and excess moisture can all allow water to enter the tank, especially if there are any small cracks or the tank is not properly secured.
Over time, moisture inside the tank can cause condensation to build up in the heating oil, increasing the risk of contamination, corrosion, and damage to your heating system. Regular tank inspections and ensuring the cap is tightly fastened can help prevent water from entering your tank.
Water contamination in your oil tank can cause serious damage to your boiler or AGA if left untreated. Because water sinks to the bottom of the tank beneath the heating oil, contamination can often go unnoticed until it begins affecting your heating system.
Over time, water in a heating oil tank can lead to corrosion, blocked fuel lines, reduced heating efficiency, and costly repairs. Identifying the signs of water contamination early can help protect your oil tank, boiler, and overall heating system from long-term damage.
In this quick guide, BoilerJuice explains the common causes of water contamination, warning signs to look out for, and practical ways to prevent problems before they become expensive.
To help prevent water contamination in your heating oil tank, it's important to carry out regular maintenance and inspections throughout the year. Taking proactive steps can help protect your boiler, improve heating efficiency, and reduce the risk of costly repairs.
Regularly inspect your tank, pipes, and fittings for signs of wear and tear, including cracks, corrosion, rust, or oil stains.
Examine the walls of your oil tank for bulging or warping, as this may indicate structural weakness and the need for a replacement tank.
Examine the walls of your oil tank for bulging or warping, as this may indicate structural weakness and the need for a replacement tank.
If you have a bunded oil tank, make sure the outer containment area is free from standing water, leaves, and debris.
Check that your tank lid and cap are tightly secured and sitting level to prevent rainwater and condensation from entering the tank.
Trim back plants, bushes, and overgrown vegetation near your oil tank to reduce excess moisture and dripping water after rainfall.
Consider using water-removal sponges or moisture-absorbing products designed for heating oil tanks to help prevent water contamination.
One of the easiest ways to check for water in your heating oil tank is by using water-finding paste. Apply the paste to the end of a long stick or dipstick and lower it to the bottom of the tank, where water usually collects beneath the oil.
Leave the stick in the tank for a few minutes before removing it. If the paste changes colour, this is a sign that water is present in the oil tank and may need to be removed to prevent contamination and heating system problems.
If you find water in your tank, it’s important to remove it. Have a look at the options below on how to remove water from the tank.
An oil tank water removal sponge will absorb the water in your tank. This sponge will remove the water without absorbing your heating oil.
There is a filter that allows you to easily drain off any water collected from your heating oil called a heating oil water trap. When you see any trapped water in the filter bowl, simply open a valve to drain the water.
Finally, the best prevention against water contamination is to keep an eye on your tank all year round. A cost-effective way to check whether you have water in your tank is to use a colour paste which can easily detect water. These tips will reduce the chances of a hefty repair bill coming your way.
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