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Heating Oil Tank Sludge Problems & Cures InspectAPedia®  -     Heating Oil Sludge: a cause of oil piping or filter clogs and loss of heat - diagnosis and prevention of heating oil tank, line, filter, nozzle clogging problems How to save on heating costs

Here we explain the causes and cures for heating system problems due to sludge in home heating oil tanks, including problems of clogged oil piping, clogged oil filters, oil burner malfunctions, and loss of heat due to sludge in the oil tank. This website answers most questions about all types of heating systems and gives important inspection, safety, and repair advice. Criticism and content suggestions are invited from heating service technicians, home inspectors, and home owners.

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Problems With Heating System Reliability When Heating Oil Additives are Used or Low-Level Oil Tanks are Filled

When we serviced and installed heating equipment we often recommended use of heating oil additives to remove small amounts of water or sludge in oil storage tanks, or to act as a pour point depressant for outdoor aboveground oil storage tanks. But while these are good products, things didn't always go well. We discuss the problem of sludge in heating oil tanks, lines, filters, and oil burner nozzles in more detail at Oil Tank Sludge Problems & Solutions

Heat System Failure (heat loss) due to Sludge Clogging of Heating Oil Lines, Filters, Nozzles, or Tanks

Why is Modern Heating Oil Showing a Sludge Problem?

When we serviced heating equipment in the early 1970's, we often found oil fired heating boilers or furnaces that had worked ok for years without any oil filter installed whatsoever!. We were amazed until we learned the history of heating oil cleanliness. We're not talking about the number of BTU's per gallon of heating oil, just how clean or dirty it is.

Before the 1970's oil crisis when much of the heating oil sold in the U.S. was from the middle east, if you put some heating oil in a bottle and examined it, it was a lovely clear yellow color, much like cooking oil. Currently (2008) heating oil in most of the U.S. is black goopy stuff with lots of large molecules that tend to settle out as black sludge in an oil tank, heating oil line, or oil filter.

Heating oil companies are not to blame for this messy stuff. Heating oil is being produced by "cold cracking" - it is chilled and centrifuged rather than distilled into clear oil as in the "old days".

A result of this change in heating oil manufacture is that even overnight in a heating oil delivery truck, a driver may see evidence that some components of heating oil in the tank are settling out as sludge material. The same thing happens in a home heating oil tank. What problems does sludge in an oil tank cause?

• Sludge in a home heating oil tank: Sludge settles to the bottom of an oil tank where, if the oil line to the oil burner exits at the tank bottom, it readily enters the oil line and over time can clog that piping system.
  
  
• Oil tank sludge leads to loss of heat: sludge, even suspended in heating oil, can clog an oil burner filter, resulting in oil burner shut down if the filter is not changed frequently enough. Heat Doctors, in Poughkeepsie, NY convinced us to install a "System 2000" High Efficiency oil fired heating boiler in a rental house. From the time of new installation we never made it through a heating season without a no-heat call for this new system.
  
  Eventually we traced the problem to sludge in the oil tank which was clogging the new, high-efficiency filter on our oil burner. Our installer suggested the solution was to install a new heating oil tank.
  
  Since the oil tank was not leaking and was otherwise in good condition, and because removing the old and installing the new tank would cost thousands of dollars we were not happy with this "advice". We asked instead for a new, larger capacity oil filter to be installed to keep oil flowing between annual service calls. That step seems to have helped.
  
  
• What else does Sludge in an Oil Tank Clog?: besides the oil line itself, sludge in the oil tank can clog the "Fire-o-Matic" safety valve on the oil line, the oil filter, the oil burner nozzle, internal strainers inside of the oil burner fuel pump, or orifices in the oil burner fuel pump unit itself. Any of these can lead to a loss of heat.

What to Do About Sludge in an Oil Tank - The Basic Problem, The Basic Solution to Oil Tank Sludge

In addressing heating oil waxing and oil line clogging in cold weather, we discussed use of oil tank additives to reduce the temperature at which this problem occurs. That article is at HEATING OIL CLOUD WAX GEL POINT. But taking our own advice taught a new lesson in oil tank sludge problems.

Sludge causes rapid oil filter clogging: We have seen problems with rapid clogging of heating oil filters and thus loss of heat from sludge that was brought out of an old oil tank and into the filter.

What Happens when we use an oil tank additive to break up sludge? When we added a pour point depressant to our heating oil we hoped it would also break up the sludge - after all, the product also claimed to break up sludge - which sounds good if the oil lines are old and perhaps partly blocked with sludge.

But in this case the combination of use of a heating oil additive with a "de-sludger" combined with the sludge agitation up from the bottom of the oil tank during filling of a nearly empty oil tank led to loss of heat from filter clogging.

Emergency Measures: what to do if you run have run out of oil and had sludge in your oil tank?: Oil companies may recommend that if you have to fill an old maybe sludgy oil tank that was nearly empty, turn off the boiler or furnace for a few hours to let the sludge return to the bottom of the tank (and be sure your heating equipment is fed fuel from the tank top tappings not from the tank bottom tapping.

Products to Gradually Remove Oil Tank Sludge Without System Clogging: An example of a heating oil additive used by some oil companies to both prevent sludge build-up in modern heating oil tanks and also to (over time) remove sludge in an existing older heating oil tank is "Ultra Guard" a product from Beckett Additives. http://www.beckettadditives.com/

One of our local heating oil delivery companies (Nash Oil, Dutchess County NY) informs us that they are the only local heating oil delivery company who uses this additive in their heating oil. The oil tank delivery truck drivers base their opinion on what they see. We're told that the interior of the Nash Heating Oil Truck Tanks is visibly clean as a result of using heating oil with a "maintenance dose" of Ultra Guard(TM).

Some heating oil technicians may recommend that a "treatment dose" of this additive be tried in an older oil tank which has been suffering from a sludge problem in the tank or oil lines. If this product works as claimed (there is evidence for it) you may be able to avoid an expensive oil tank replacement for an older oil tank which is sludge-contaminated but not leaking. Ask your heating oil company about this or similar products.

Note that this product is not a pour point depressant to avoid waxing or gelling, but sludge, too, can lead to a loss of heat which may be exacerbated in cold weather. (More frequent deliveries, running the oil tank too low on oil, stirring up sludge during oil delivery, clogging the oil burner filter or nozzle as sludge passes through the system all can lead to loss of heat in a building.

A List of Priorities & Steps to Correct Sludge Problems in a Heating Oil Tank

We are not sure how much trouble someone wants to go through in dealing with oil tank sludge, but because tank replacement is so costly I would take several steps to try to work out the sludge problem without replacing an old sludgy but otherwise good-condition oil tank.

• Emergency Oil Tank Sludge Measure - Turn off The Heat: If you know that the oil tank has a sludge problem, if you can't do anything else, at least try turning off the heat for a time during and after the oil delivery. (Don't let the building get so cold that pipes freeze or other damage occurs.) We MIGHT have avoided our oil filter sludge-clog problem discussed above if we'd been able to keep the heat OFF for 3 to 6 hours from the time of the delivery. The idea is to let the worst of the sludge stirred by the delivery settle out to the tank bottom.
  
  
• Emergency Oil Tank Sludge Has Clogged Oil Lines - Line Blowout: If the oil line(s) from tank to burner become badly clogged with oil tank sludge, you need help from a heating oil service technician. Sludge often clogs heating oil lines, especially if the oil lines leave the bottom of the oil tank en route to the burner. A service tech finding a clogged oil line (diagnosed by opening the oil line at the burner or by measuring the line vacuum when the burner fuel unit is running) can temporarily "blow out" sludge in the line using a CO2 cartridge and special fittings.
  
  This is a short term fix that may keep things going until the sludge has been removed. It usually works but not always. If the CO2 blowout fails you need to replace oil lines between tank and burner as well as deal with the sludge. Oil lines that come off of the top of the tank, since they don't pick up oil (and sludge) from the very bottom of the tank, will be less prone to clog by sludge in the oil tank, so this is another approach to consider if sludge-clogged oil lines between oil tank and burner are a problem.
  
  
• Ultra-Guard(TM) heating oil additive won't un-clog a blocked heating oil line but heating oil additives can be used to break up sludge rapidly (watch out!) or gradually by using the additive in a "treatment dose". Treatment doses of sludge breakup chemicals can be added by an oil company who has that product - not all companies carry it since it adds cost to their heating oil deliveries.
  
  I don't think you can buy it yourself in a consumer-sized quantity. (Let me know if your local suppliers will sell it to you - I'm doubtful). The "maintenance dose" of Ultra guard � included by a heating oil company in an oil delivery will probably be insufficient, at least in just one or two oil deliveries, as a "cure" for a serious sludge problem if yo are already seeing sludge clogging.
  
  
• Other sludge break-up products which can be added to an oil tank (4-In-One Hot (TM) was an example I tried) might also work to remove sludge (as well as water and also to avoid waxing or cold weather jelling or waxing of heating oil in the case of some products) and are commonly available from many oil companies. These heating oil additive products are always added manually to an oil tank whereas a "maintenance dose" of UltraGuard™ (and there may be other products like it) is included in heating oil deliveries by some oil companies (not all of them).
  
  
• Sludge treatments can also lead to an immediate problem even though they're "fixing" the sludge: As I discussed above, it was using one of these other sludge-break-up products in an oil tank that taught me that the de-sludger can also contribute to a no-heat call IF its use is combined with an oil fill-up of a sludgy-oil tank which was run nearly out of or fully out of oil - the delivery stirred up the sludge, probably more so because of my additive, and the stirred goop immediately clogged the oil filters at my oil burner leading to loss of heat.
  
  
• Handle Oil Tank Sludge By Increasing Heating Oil Filter Capacity: This approach can keep the heat working while we're waiting for our sludge solvents to do their job over a longer time. In a property where we were having sludge clogging problems at the filter but where the oil tank was both in good condition and also difficult to remove even if we wanted to, we took a much less costly approach by doubling the oil filters.
  
  Adding a high capacity oil filter at the burner, or adding two oil filters in parallel at the oil burner should not be too costly and is another way to keep the oil burner going when sludge is moving through the oil lines to the burner where it might otherwise clog a filter, strainer, or nozzle.
  
  
• Replacing a sludged heating oil tank is a last resort: even though your oil company will take the safe route and recommend this much more costly solution, you may not need to replace your sludge-contaminated heating oil tank UNLESS the heating oil tank is itself one that should be replaced for other reasons anyway, such as:
  • You have an oil tank which is buried and can be replaced by one that is indoors and less of an environmental risk.
  • You have an oil tank which is leaky and needs replacement anyway.
  • You have an old oil tank which is not yet leaking but is in badly rusted condition with indications that rust perforation is a serious risk.

What to Do About Sludge in the Oil Storage Tank - Suggestions

What the Oil Company Recommends for Sludgy Old Oil Tanks:

The oil company will advise you to replace the tank - that's the safest advice for them to give, doesn't cost them a dime, and is most profitable too. The concern faced by the oil company is whether or not the sludgy tank will

• result in a loss of heat, burst pipes, water damage, costly mold cleanup
• leak into the building resulting in a costly oil spill cleanup.

The oil company is concerned that these problems are most likely to occur when an oil tank is being stressed by the increase in pressure that occurs in the tank during fill-up. That pressure increase risk is still greater if the tank is not properly vented or if the tank vent is clogged.

Possible Alternatives to Replacing a Sludged Oil Tank

A possible alternative to simply replacing an old oil storage is to have the tank steel thickness measured - if the tank is not corroded and thus not at unusual risk of failure, it makes sense to try to clean out the sludge - a service some oil companies can provide.

If your oil company provides a tank cleaning service we recommend that step. The sludge, debris, and water in the tank are removed by a vacuuming procedure. Because these contaminants are normally sitting on the bottom of the oil tank, this procedure can be used even when the tank is full of heating oil.

You can add an oil tank additive like 4-in-one hot that also breaks up sludge, but if there is a lot of it in the tank it could take a very long time to pass the suspended sludge out and risks clogging the oil filters (and loss of heat) to boot. When adding an oil tank pour point depressant that also is intended to remove water and also to break up sludge in the oil tank, the risk is that the additional suspended sludge caused by the additive, especially right after filling a low-nearly-empty oil tank will clog the oil filters. See A Guide to No. 2 Heating Oil Waxing, Gelling, or Clouding - for a discussion of additives.

What we recommend if you are unable to find a local company who can remove the oil tank sludge:

• Test and confirm that the tank steel thickness meets minimum standards. If the tank steel thickness does not meet your oil company's recommendations, the tank should be replaced.
• Inspect and confirm no visual evidence of oil tank or oil piping leaks, damage, or improper/unsafe/leak-prone oil fill, vent, or delivery piping such as plastic piping or under-sized vent.
• Instruct the property occupants not to let the tank get to "empty" before re-filling it - filling a nearly empty tank stirs up more sludge and risks clogging the oil filter.
• Clear any clogged oil lines between tank and burner, or simply replace these lines.
• Route oil lines out of the top of the oil tank that delivers oil to the burner, not out of the tank bottom. This installation will keep the oil pick-up pipe inside the oil tank a few inches from the bottom, or above the sludge top. If your oil tank piping uses a two-pipe system (supply line and return line to the tanks) then sometimes swapping the role of the two lines will help clear out a partly-blocked supply line.
• Where a pair of tanks is installed, wait until the tanks are nearly empty and, catching any spillage, replace the oil line that is intended to flow oil between the two tanks.
• Blowing out a clogged oil delivery line with a CO2 cartridge may help, but as long as that oil pipe has to be disconnected to do the blowout, it may be a better long term solution to just replace it. If a larger diameter line can be fitted, better still.
• Install a pair of double-sized oil filters in parallel on the oil line at the oil burner - this helps assure that heat will keep running without oil filter clogging between annual maintenance service calls (when the filter cartridges are replaced).

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HEATING LOSS DIAGNOSIS-BOILERS
HEATING LOSS DIAGNOSIS-FURNACES
HEATING OIL CLOUD WAX GEL POINT
HEATING OIL SHELF LIFE
HEATING OIL SLUDGE

ODORS FROM HEATING SYSTEMS
OIL BURNERS
OIL BURNER INSPECTION GUIDE
OIL BURNER NOISE SMOKE ODORS
OIL BURNER SOOT & PUFFBACKS
OIL FUEL TYPES & CHARACTERISTICS
Oil Odors: Leaky Oil Tank Piping
OIL SAFETY VALVES
OIL TANKS
OIL TANK GAUGES
OIL TANK LEAKS
OIL TANK SLUDGE
OIL TANK TESTING
OIL TANKS, BURIED

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

• Our recommended books about building design, inspection, and repair, and about indoor environment testing, diagnosis, and cleanup are at the InspectAPedia Bookstore.
• Carbon Monoxide Gas Toxicity, exposure limits, poisoning symptoms, and inspecting buildings for CO hazards
• Oil Tanks - The Oil Storage Tank Information Website: Buried or Above Ground Oil Tank Inspection, Testing, Cleanup, Abandonment of Oil Tanks
• Oil Tanks Above Ground, UL Standards, guidance for home owners, buyers, and inspectors
• Domestic and Commercial Oil Burners, Charles H. Burkhardt, McGraw Hill Book Company, New York 3rd Ed 1969.
• National Fuel Gas Code (Z223.1) $16.00 and National Fuel Gas Code Handbook (Z223.2) $47.00 American Gas Association (A.G.A.), 1515 Wilson Boulevard, Arlington, VA 22209 also available from National Fire Protection Association, Batterymarch Park, Quincy, MA 02269. Fundamentals of Gas Appliance Venting and Ventilation, 1985, American Gas Association Laboratories, Engineering Services Department. American Gas Association, 1515 Wilson Boulevard, Arlington, VA 22209. Catalog #XHO585. Reprinted 1989.
• The Steam Book, 1984, Training and Education Department, Fluid Handling Division, ITT [probably out of print, possibly available from several home inspection supply companies] Fuel Oil and Oil Heat Magazine, October 1990, offers an update,
• Principles of Steam Heating, $13.25 includes postage. Fuel oil & Oil Heat Magazine, 389 Passaic Ave., Fairfield, NJ 07004.
• The Lost Art of Steam Heating, Dan Holohan, 516-579-3046 FAX
• Principles of Steam Heating, Dan Holohan, technical editor of Fuel Oil and Oil Heat magazine, 389 Passaic Ave., Fairfield, NJ 07004 ($12.+1.25 postage/handling).
• "Residential Steam Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
• "Residential Hydronic (circulating hot water) Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
• "Warm Air Heating Systems". Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
• Heating, Ventilating, and Air Conditioning Volume I, Heating Fundamentals,
• Boilers, Boiler Conversions, James E. Brumbaugh, ISBN 0-672-23389-4 (v. 1) Volume II, Oil, Gas, and Coal Burners, Controls, Ducts, Piping, Valves, James E. Brumbaugh, ISBN 0-672-23390-7 (v. 2) Volume III, Radiant Heating, Water Heaters, Ventilation, Air Conditioning, Heat Pumps, Air Cleaners, James E. Brumbaugh, ISBN 0-672-23383-5 (v. 3) or ISBN 0-672-23380-0 (set) Special Sales Director, Macmillan Publishing Co., 866 Third Ave., New York, NY 10022. Macmillan Publishing Co., NY
• Installation Guide for Residential Hydronic Heating Systems
• Installation Guide #200, The Hydronics Institute, 35 Russo Place, Berkeley Heights, NJ 07922
• The ABC's of Retention Head Oil Burners, National Association of Oil Heat Service Managers, TM 115, National Old Timers' Association of the Energy Industry, PO Box 168, Mineola, NY 11501. (Excellent tips on spotting problems on oil-fired heating equipment. Booklet.)
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