Heating Boiler, Furnace or Water Heater Oil Line De-Clogging Guide
InspectAPedia^® -

Causes of fuel oil piping clogging and blockage: oil tank sludge, water, waxing fuel, kinks, dirt, rust, etc.
Cures for oil line blocked: how do you de-clog or un-block a clogged heating oil fuel line?
Guide to Unclogging a blocked furnace, boiler, or water heater fuel oil pipe line
Where to buy & how to use hand pumps, fittings, vacuum gauges, pressure gauges, & CO₂ blowout guns to diagnose, test, & repair clogged fuel oil piping lines
Questions & Answers about how to de-clog a furnace oil line, or a clogged boiler or water heater oil pipe line

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.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers nor with topics or services discussed at this website.

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.

© Copyright 2012 InspectAPedia.com, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use page top links to major topics or use links at the left of each page to navigate within topics and documents at this website. Green links show where you are in a document series or at this website.

How to clear or un-block a clogged heating oil line

Symptoms of furnace, boiler, or water heater oil line clogging

Often there are symptoms of a clog or blockage problem developing in a heating appliance oil line before the line is totally blocked.

These can include intermittent failures of the oil burner to ignite or to keep running, the system going "off on reset", a poor oil burner flame, and ultimately simply loss of heat when the burner will no longer start.

If your heating appliance includes an oil vacuum gauge on the oil piping (sometimes but not usually installed) you may see abnormally high oil line vacuum readings - the fuel unit is sucking away on the oil line but is having trouble pulling oil through the system.

Keep in mind that a high vacuum can also develop if the gauge is downstream from a blocked or dirty oil filter. Vacuums greater than minus-10 psi may indicate a blockage.

Westwood Products [2] and other suppliers distribute pump tester gauge sets (Reillo pump testers and vac-probe oil line access port testers) that can als be used to detect problems with the heating appliance fuel piping system such as blockages and leaks.

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

A bend or kink in the oil line that reduces flow and collects debris upstream of the blockage
Sludge passing from the oil tank out into the fuel line, particularly in systems whose oil piping is supplied from a connection at the bottom of the oil tank
Mud or other crud that enters the oil tank or heating equipment when a building is flooded during a storm, hurricane, etc. - see Question: how to get the heating oil line flowing after hurricane & flood damage
Rust from an oil tank entering the oil piping
Heating equipment being left off for long periods of time
Heating oil that waxes or gels due to exposure to cold weather where the oil storage tank is located outdoors or is otherwise in an unheated area - see HEATING OIL CLOUD WAX GEL POINT
Water or ice entering or blocking the heating fuel oil line in freezing climates where the oil storage tank is located outdoors or is otherwise in an unheated area - see OIL TANK WATER CONTAMINATION and also OIL TANK WATER REMOVAL

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.

If no pressure develops, then the oil line is clear.
If pressure is developed but falls, you may be successfully pushing the blockage back into the oil tank. If pressure is developed and does not fall, the oil line is blocked and you are not clearing it.

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

Before assuming that the heating oil line has become clogged with sludge, rust, waxed heating oil or ice, check the oil filter condition.

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:

a CO₂ blowout gun is attached to the oil line at the fuel unit and used to send a blast of carbon dioxide backwards through the oil supply line
a hand pump is attached at the oil line and is used to try to clear the oil line
a small canister of compressed air along with appropriate fittings is used as the CO₂ blowout gun method

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).

CO₂ blowout guns and replacement CO₂ cartridges are sold by HVAC suppliers, including Westwood Products.[2 ]

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

If the heating oil line cannot be cleared with one to three blast-out tries using the CO₂ cartridge, the heating service tech will most likely recommend replacing the oil piping.

We recommend using newer plastic-coated oil lines for better protection from corrosion and /or mechanical damage.

If the old oil line was just 3/8" ID or smaller, you might want to go to a 1/2" ID oil line to further protect against clogging in the future.

At "Question: how to get the heating oil line flowing after hurricane & flood damage" we describe using a CO-2 canister and cartridge to try to blast open a sludge or mud or debris-clogged fuel oil pipe or line following a building flood.

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.

Reply:

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. [2][3][4]

Questions & Answers regarding this article

Questions & Answers about how to de-clog a furnace oil line, or a clogged boiler or water heater oil pipe line.

Ask a Question or Search InspectAPedia

HTML Comment Box is loading comments...

Recommend / Share this Article

...

Technical Reviewers & References

InspectAPedia.com^® - Daniel Friedman - Publisher & Editor.
InspectAPedia Bookstore lists recommended books, organized by topic & available for purchase. Most of our articles also list books on the specific article topic as well as other references, and information sources.
Critique, contributions wanted: Contact Us to suggest corrections or additions to articles at this website, and if you wish, to receive online listing and credit as a contributor. Particular thanks are due to the many experts and also consumers who read and critique technical articles at InspectAPedia.com.
Additional technical contributors & reference sources for this article are listed below.

Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

OIL LINE CLOGGING FIX

OIL TANK PIPING & PIPING DEFECTS

[1] "Fuel Oil Piping and Storage", 2006 Mechanical Code, Chapter 13, International Code Council, 500 New Jersey Avenue, NW, 6th Floor, Washington, DC 20001, Tel: 888-ICC-SAFE (422-7233); Website: iccsafe.org/, Email: webmaster@iccsafe.org, Customer Store (buy publications) 800-786-4452. Also see 2009 International Codes and 2012 International Codes.
[2] Westwood Products Inc., 330 William St., PO Box 610, South River, NJ 08882-0610 Phone: (732) 651-7700 Toll-Free: (800) 442-1630, Website: westwoodproducts.com, emailwestwoodproducts.com
[3] Mitco Manufacturing, 137 Puncheon Creek Drive, Andrews SC 29510, Tel: 800-338-903, website: mitcomfg.com also produces tools for clearing plugged heating equipment oil lines including their4 Kwik-Purge CO₂ Blow-out Gun.
[4] Charles Gallo Drain Gun, uses CO₂ to blow out A/C condensate drain line clogs, is distributed by DiversiTech Corporation 6650 Sugarloaf Parkway Duluth, GA 30097 800.995.2222 Website: diversitech.com. This tool includes an adapter kit to allow use of the blowout gun on oil burner lines.
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. Thanks to Alan Carson and Bob Dunlop, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education including the ASHI-adopted Home Inspection Training Program (home study course), publications such as the Home Reference Book, report writing materials including the Horizon report writer, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
Arlene Puentes, an ASHI home inspector in Kingston, NY, contributed the example photograph of an outdoor aboveground oil tank. Ms. Puentes can be contacted at ap@octoberhome.com
Audels Oil Burner Guide, Installation, Servicing, Repairing, Frank D. Graham, 1940's edition (obsolete). Updated versions of this guide are available in various editions, 1947, 1950, 1955, 1958, 1959, 1962, 1965, 1967, and at prices from around $3.00 to nearly $70.00 - useful for simple, clear, but not current, explanation of how heating equipment works. The original retail price was $1.00.
Dave Ferris - M&S Environmental Systems, Dutchess County, New York. Mr. Ferris was an HVAC expert. Personal communication to DJF 1987. Remove the firematic or fusible oil supply line valve on return oil-line side - in case of fire if this one closes first the pump continues to run, blows its seal, and sprays oil all over the fire. Proper installation is to have a fusible link valve only on the supply side, and to install a check valve on the return line to prevent back-siphonage from the tank.
"HUD Regulation for Manufactured Homes; Requirement that Heat-Tape not include a GFCI [ copy on file as /plumbing/GFCI_Heat_Tapes_HUD_CPSC_Letter1994.pdf ] - ", Meeting Log, US CPSC, HUD, Dennis McCoskrie, ESEE, 2/14/1994

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
...

Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair

Ask a Question or Search InspectAPedia

How to clear or un-block a clogged heating oil line

Symptoms of furnace, boiler, or water heater oil line clogging

What causes a heating appliance fuel oil line to become blocked?

How to Confirm that a Heating Oil Line is Blocked

How to De-Clog or Un-Block a Clogged Heating Oil Fuel Liine

First check the oil filter for clogging or blockage

Try using a pressure and vacuum hand pump or a CO2 blowout gun with CO2 cartridge to blast open a clogged heating oil line

Emergency steps to keep heat running with a clogged oil line

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

Reply:

Questions & Answers regarding this article

Ask a Question or Search InspectAPedia

Technical Reviewers & References

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

Try using a pressure and vacuum hand pump or a CO₂ blowout gun with CO₂ cartridge to blast open a clogged heating oil line

Question: Where to buy CO₂ cartridges and gun for cleaning out #2 fuel oil lines from tank to burner