Oil tank maintenance — what you need to do every year
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Most likely cause & what to check
Inspect the tank exterior annually for cracks, dents, rust, or UV degradation (if plastic). Bunded (double-skin) tanks are now required in most installations — check the outer skin for oil staining.
Check all fittings and connections for weeping or dripping oil. Any oil leak from a domestic tank must be reported to the Environment Agency and cleaned up — you can be held personally liable for contamination costs.
Test the bottom tank outlet and fire valve — this should be easy to close in an emergency. If the valve is stiff or leaking, have it replaced.
Have the tank cleaned and sludge removed every 3–5 years. Water and microbial contamination (fuel bugs) settle at the bottom of oil tanks and cause filter blockages and boiler lockouts.
Add a biocide treatment annually to prevent microbial growth — available from oil suppliers. Also add a stabiliser if the tank is not used over summer to prevent fuel degradation.
Check the vent pipe and filter housing for blockages — wasps are particularly fond of nesting in oil tank vents. A blocked vent creates a vacuum and stops oil flowing.
Ensure the tank is level and the legs or supports are structurally sound. A collapsing tank is an oil spill waiting to happen. Check for ground subsidence under plastic-legged tanks.
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