How to Clean a Filter on an Outside Oil Tank Safely, or Replace the Filter

How do you change the filter on a heating oil tank?

Turn off the furnace or boiler power, close the oil shut-off valve at the tank, catch drips in a pan, swap the filter cartridge and gasket, then reopen the valve, restore power and bleed air from the burner pump until oil flows steadily. Check for leaks while the burner runs.

Do not clean a used cartridge with solvent or gasoline. Replace it. If you smell strong fuel, see sludge or water, or have a leak, stop and call a licensed technician.

Safety and supplies before you start

• Heating oil is flammable. No smoking, open flames or sparks nearby, and never work while the burner is running.
• Wear gloves and eye protection. Heating oil can irritate skin.
• Have a drip pan, rags, absorbent pads and a sealable container for old parts.
• Buy the exact replacement filter and gasket for your canister or spin-on housing. Check the model on the old part.
• Many homeowners do this themselves, but local rules and your insurer may require a licensed technician. Check before you start.

The filter normally sits on the oil line between the tank and the burner pump, often near the tank. Some filters mount directly on the tank outlet. Most residential tanks have no internal filter.

How to change a heating oil filter: 10 steps

1. Switch off power to the furnace or boiler at the emergency switch.
2. Close the oil shut-off valve at the tank. Lever valves are closed when the handle is across the pipe. Some stem valves close in the opposite direction from what you expect, so check the valve.
3. Put a drip pan under the filter.
4. Open the housing: unscrew the canister base, or use a filter wrench on a spin-on filter.
5. Remove the old cartridge and gasket. Do not reuse the gasket.
6. Wipe the inside of the canister with a clean rag. Note any sludge or water. Heavy sludge means the tank may need service.
7. Fit the new cartridge and a new gasket in the same orientation as the old one. Hand-tighten the housing and do not over-tighten.
8. Open the shut-off valve slowly and check the filter for leaks.
9. Restore power and bleed air from the burner pump.
10. Watch the burner run for several minutes. Look for leaks, steady ignition and normal operation.

Replace the filter about once a year, ideally before the heating season, and again mid-season if you see clogging or poor performance.

How to bleed air from the oil line after changing the filter

Air in the line can make the burner fail to ignite or shut down. Follow your burner manual, and in general:

1. Find the bleeder valve on the burner pump, or the vent screw on the filter housing.
2. Hold a container under it, and open it a little while the burner runs.
3. Close the valve as soon as oil flows steadily with no bubbles.
4. Let the burner run and confirm it stays lit.

If the burner locks out, limit resets to what the manual allows. Repeated resets are not safe. If it keeps locking out, call a technician.

When to call a licensed heating technician

• You smell strong fuel oil, or see oil on the floor or ground. Shut off the burner and valve if it is safe, ventilate, and call your fuel supplier or technician. Follow your state’s spill reporting rules.
• The filter shows water, heavy sludge or rust, which can mean tank problems.
• The tank or lines are buried or damaged, or the shut-off valve will not close.
• The burner will not stay lit after bleeding, or keeps locking out.
• You are not sure what you are doing. A service call is cheaper than a spill cleanup.

Dispose of the old filter and any oil responsibly. Check your local household hazardous waste site, and read our guide on where to dispose of used oil.

Oil tank filter FAQ