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OIL STORAGE TANKS
ABANDONING OIL TANKS
AGE of OIL TANK
ANODES & DIP TUBES on WATER HEATERS
BURIED OIL TANK ADVICE
BURIED OIL TANKS, FINDING
COMBUSTION PRODUCTS & IAQ
DEFINITION of Heating & Cooling Terms
DIAGNOSE & FIX HEATING PROBLEMS-BOILER
DIAGNOSE & FIX HEATING PROBLEMS-FURNACE
DIRECTORY of OIL TANK EXPERTS
FILTERS, OIL on HEATING EQUIPMENT
FIRE SAFETY CONTROLS
FLOATING UP OIL STORAGE or SEPTIC TANKS
FLOODED HEATING EQUIPMENT REPAIR
FLOODED WATER HEATER REPAIR
FUEL OIL TYPES & CHARACTERISTICS
FUEL UNIT, HEATING OIL PUMPS
GALVANIC SCALE & METAL CORROSION
GAUGES ON HEATING EQUIPMENT
HEAT TAPES, Heat, Insulation prevent Freeze-Up
HEATING COST FUEL & BTU Cost Table
HEATING COST SAVINGS METHODS
HEATING OIL CLOUD WAX GEL POINT
HEATING OIL EXPOSURE HAZARDS, LIMITS
HEATING OIL - OLD, USEABLE?
HEATING OIL PIPING TROUBLES
HEATING OIL SHELF LIFE
HEATING OIL SLUDGE
HEATING OIL TANKS
HEATING OIL TYPES & PROPERTIES
HEATING OIL USAGE RATE
HEATING SYSTEM NOISES
HOME BUYERS GUIDE TO OIL TANKS
NOISE CONTROL for HEATING SYSTEMS
NOISES COMING FROM WATER HEATER
ODORS & SMELLS DIAGNOSIS & CURE
ODORS FROM HEATING SYSTEMS
OIL FILTERS on HEATING EQUIPMENT
OIL FUEL TYPES & CHARACTERISTICS
OIL FILL PIPE LEAKS
OIL SPILL CLEANUP / PREVENTION
SOOT on OIL FIRED HEATING EQUIPMENT
STAIN DIAGNOSIS on BUILDING INTERIORS
THERMAL TRACKING & HEAT LOSS
VIDEO GUIDES: Heating System Videos
VIDEO GUIDES - InspectAPedia.com
WINTERIZE A BUILDING
This article describes the causes and cures of blocked or clogged fuel oil piping or lines that are used to deliver heating oil to oil fired furnaces, boilers, or water heaters. We give emergency steps to keep heat working when the oil line is blocked and we describe alternatives to try before going on to replace an old clogged fuel oil pipe line.
We discuss using vacuum gauges, pressure gauges, and both hand pumps and CO2 blowout guns to diagnose, test, & repair clogged fuel oil piping lines. Also see HEATING OIL SLUDGE and review OIL TANK PIPING & PIPING DEFECTS.
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Symptoms of furnace, boiler, or water heater oil line clogging
What causes a heating appliance fuel oil line to become blocked?
Fuel oil piping for oil fired furnaces,oil fired heating boilers, and oil fired water heaters can become blocked due to
How to Confirm that a Heating Oil Line is Blocked
Start by checking vacuum gauge readings on the oil line as we described above.
A hand pump or CO2 cartridge oil line blowout gun can be used to pressurize the oil line between its (for this purpose disconnected) end at the oil filter and its inlet at the oil tank.
How to De-Clog or Un-Block a Clogged Heating Oil Fuel Liine
Remedies for a clogged heating oil line depend in part on an assessment of just why the line has become blocked. IN the list above we give links to some oil line blockage problem causes and solutions.
First check the oil filter for clogging or blockage
Open the oil filter canister and take a look for thick goop inside the canister and on the outside of the oil filter cartridge itself.
Pull out (and dispose of) the oil filter itself. Now look in the bottom of the oil filter canister base for thick deposits of goop.
Clean that mess out. Also look for rust in the canister bottom - an indicator of excessive water in the oil storage tank.
Now replace the canister filter, reassemble the unit, bleed out the air from the unit, and check for functional oil flow. More details are at OIL FILTERS on HEATING EQUIPMENT.
Try using a pressure and vacuum hand pump or a CO2 blowout gun with CO2 cartridge to blast open a clogged heating oil line
More generally, if the heating service tech thinks that the oil line is blocked by sludge or debris, before replacing the line s/he will often attempt to blast the debris and crud backwards from the connection at the oil burner all the way back into the oil tank. There are three approaches we've seen HVAC techs use:
Why might that approach work? Because it's common for some sludge to accumulate in the bottom of older oil tanks; the tank is installed (or should be) pitched slightly away from its bottom oil outlet port so that oil tank sludge or water that collects there (as long as it's not too much or too deep) will be kept away from the oil line.
Heating oil line cleanout or blasting is attempted using compressed air or more commonly a small portable canister whose end fittings accept a connection to the oil line flare fitting. The canister's other end accepts a CO2 cartridge. When the service tech screws the oil line blaster canister cartridge fully shut, a pin opens the CO2 cartridge, sending a blast of carbon dioxide backwards through the oil line.
If this quick and easy approach clears the oil line, you're back in business. (One may still need to bleed air from the oil piping lines after the fittings are reconnected).
Watch out: excessive pressures applied to the heating oil line can damage the piping, blow out the line, fittings, or other components, and can cause an oil spill in the building. Some oil line blowout gun models include a built-in safety valve to limit the outlet pressure to 150 psi to avoid this hazard.
Watch out: using a blowout gun or any high pressure method to try to clear a buried oil line is dangerous. The risk is that you create an underground oil leak - very costly to clean-up and repair. I'd use a hand pump or the (more popular) CO2 blowout gun that limits its output pressure to within the design range of the oil piping system, and I prefer to use only very low pressures to feel your way into clogs in buried oil lines.
Emergency steps to keep heat running with a clogged oil line
For buried oil tanks or other oil tank installations that use a dual oil line piping arrangement, one oil line is the supply (the one that has become clogged) and the second line is a return pipe that sends excess oil back to the oil storage tank.
Typically these installations insert the two oil lines through the top of the oil storage tank, and down into the tank to perhaps 6" from the tank bottom, and spread apart several feet (by bending the lines) so that the agitation of oil tank bottom sludge caused by the returning oil does not send sludge up through the oil pickup pipe.
If this is the arrangement at your oil tank and provided that the problem oil line is not totally blocked, we might keep heat running by temporarily switching the roles of the oil feed and oil return pipe.
That's because oil flowing backwards from the oil burner fuel unit (oil pump) to the oil tank has been filtered (before entering the oil pump) and will be less likely to have already clogged the return line.
Our dual heating oil line photo (above left) shows that just one oil line is in use at this oil fired heating furnace. Further investigation is needed to determine if the capped oil line is an old abandoned sludge-clogged oil pipe or if the system is limping along having been converted to a single oil line set-up.
Watch out: don't swap the oil supply and return line roles if one of these lines (probably the original supply line) is totally blocked.
Doing so can damage the oil pump at the oil burner, or worse, cause a dangerous leak of oil into the building if the higher pressure on the return line (caused by a blocked oil pipe) causes the oil pump (fuel unit) to blow a gasket.
Watch out: in a few oil tank installations at which a dual oil pipe system was installed on a oil tank that is located above ground, it may be possible to temporarily keep heat running by converting back to a single oil line system, using the "return line" now as the oil supply line.
But the oil pump unit on the oil burner will also have to be changed back to a single-oil line set-up. An internal bypass valve plug needs to be correctly installed for the fuel unit oil pump to work safely and correctly.
Replace clogged heating oil lines
Frequently Asked Questions (FAQs) about the cause and cure for blocked or clogged furnace, boiler, or water heater fuel oil line
Question: Where to buy CO2 cartridges and gun for cleaning out #2 fuel oil lines from tank to burner
I need to buy CO2 cartridges and gun for cleaning out #2 fuel oil lines. Please tell me where I can get these in Manhattan or brooklyn. Wouild home depot carry this? Thanks, D.G.
The CO2 oil line blow out gun or "oil line blaster tool" that I have and use takes a CO2 cartridge that is a bit bigger than the ones commonly sold for use in seltzer makers and similar devices. I purchase refills at my local plumbing supplier who sells HVAC tools and equipment.
If you do not have a convenient local supplier for heating system test and repair tools, you can also contact the oil line plug repair tools distributors listed in the references section of this article, just below. 
Questions & answers or comments about how to de-clog a furnace oil line, or a clogged boiler or water heater oil pipe line.
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.