Guide to Heating Oil Piping Defects & Leaks InspectAPedia® -
Heating oil piping errors, defects, leaks, and safety hazards
Heating oil piping leaks, loss of heat, oil burner puffback causes
Heating oil tank fill and vent pipe requirements
Where should oil line fire safety valves and check valves be located?
How to de-clog a blocked heating oil line pipe or tubing
Questions & answers about fuel oil piping for oil-fired heating equipment & water heaters
This oil burner fuel piping article describes defects in heating oil piping, filters, safety valves, and oil tank fill and vent piping. All of these oil storage tank and piping installation defects can easily be found by visual inspection. We include considerations of oil pipe leaks out (fuel oil leaks), oil piping leaks in (air in the system), clogged, damaged, noisy, or mis-routed fuel oil piping, and oil fill and vent piping size and location requirements. We also discuss the need for and location for heating oil or fuel oil filters and safety valves.
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Beyond the costly problem of leaky oil piping, this document lists other important safety or
oil-fired equipment operational defects in home and light commercial heating oil storage and piping systems. If your heating appliance fuel is LP gas or natural gas, see GAS PIPING, VALVES, CONTROLS.
OIL PIPING LAYOUTS & OIL TANK PIPING DEFECTS - Reporting Oil Piping Defects by Visual Inspection
Here we also include sample home inspection report language that may assist home owners or home buyers in understanding
risks associated with both buried and above ground oil or other fuel storage tanks at their property.
The oil tank and oil piping inspection report language explains the need for action and indicates where
more information can be obtained.
Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.
Also see text and oil tank defect photographs at Visual Inspection of Oil Storage Tanks.
NOTICE: while example report language is provided here, reproduction of this or any of our web pages or their contents online at other websites
or in printed documents for sale is prohibited. Readers are welcome to use the text directly in home inspection reports, with citation of the website source.
UNDERSIZED OIL FILL & VENT PIPES
As Carson Dunlop's sketch shows, oil filler or vent piping that is too small can result in too much pressure in the oil tank during filling, resulting in a burst oil tank and serious oil leakage.
Oil tanks are usually filled under pressure (not by gravity like your car). We also do not like to see plastic oil piping used for these applications, out of concern that it may be broken, leading to a serious oil spill.
Carson Dunlop's sketch at left shows typical oil fill and vent piping details for an oil tank installed inside of a building. Usually these pipes are located together and against the building wall.
Sometimes we see that the oil filler pipe for an outdoor buried oil tank will be directly over the tank (and perhaps too close to ground level to keep water out), while the installer may have placed the vent pipe some distance away, against the building wall.
This may have seemed to be a neat job for the installer, but you should know that the oil delivery driver listens to the oil vent pipe to hear when the oil tank has been filled. Placing the vent line too far from the oil tank fill line is risky.
OIL FILL OR VENT PIPE CAPS LOST
As Carson Dunlop's sketch shows (above left) and as we show in Arlene Puentes' photo (above right), you are asking for water in the heating oil tank or insects clogging the fill or vent line (probably the vent line) if the caps have been lost from these pipes.
We've been informed of oil tank fill difficulties (perhaps even leading to a burst or oil tank leak) when insects clogged the oil tank vent pipe.
If the screen is lost from your oil tank vent pipe be sure to replace it to keep the wasps and mud-daubers out of this line. And be sure the screen on the oil tank vent pipe has not been blocked by painting over it - as we explain at OIL TANK PRESSURE for an explanation. this can cause an oil tank leak during an oil delivery.
NO OIL TANK VENT PIPE - Oil Tank - No Vent Pipe or Blocked Oil Tank Vent Pipe
Be sure that you can find a proper oil tank vent pipe. On occasion we find that a filler pipe was installed but no vent pipe was run outside. Improper oil tank venting such as no tank vent at all, a too-small oil tank vent, or a vent which is improperly installed, routed, or has become blocked, can cause a catastrophic oil spill in a building or outdoors at a buried tank. See OIL TANK PRESSURE for an explanation.
Oil fumes and even heating oil may spill into the building. The tank should be
vented to outside to avoid dumping noxious and possibly combustible or obnoxious fumes into
the living area.
OIL FILL PIPE EXPOSED - Oil Tank - Fill Pipe Exposed to Roof Drainage
Check to see if the oil tank fill pipe is in a location where roof drainage may fall directly on or into it.
Water in an oil tank can lead to loss of heat and costly related damage from that condition or
it can accelerate rust and corrosion from inside the oil tank, leading to oil leaks and a costly
environmental cleanup. The tank should be tested for the amount of water in it and if in question,
it should be tested for leaks. And protect the fill pipe and vent from water entry. Details are at
CAULK OIL TANK FILL & VENT PIPE ENTRANCES - Oil Tank - Caulk pipe entrances
You should caulk the opening where tank supply and vent pipes
penetrate the house wall, to prevent pest or water entry at this point. This is
an inexpensive item. This repair/maintenance item may be deferred.
OIL LINE EXPOSED - Oil Line Exposed to Damage
Check to see if the the oil lines are exposed atop the floor where they can be stepped-on. These flexible copper lines can be easily damaged, causing loss of heat or dangerous leaks.
The heating oil piping lines should be protected by means approved by your heating service professional. This should be an inexpensive
SINGLE HIGH OIL LINE - Oil Line Problem: single line routed high may lose prime
SERVICE NOTE: if an oil burner's fuel unit is served by a single line from a buried oil tank, or if the oil line is routed from even an indoor heating oil tank up high beneath the ceiling and back down to the oil burner, in some circumstances this installation may tend to lose prime in oil piping system, become air locked, or these events can lead to loss of heat and possible damage to the building from frozen pipes.
This problem occurs commonly if the oil tank is remote and buried (oil burner pumps don't have much lift capacity), or when an indoor tank is very low on oil. You should review this installation
detail with your service person.
See our discussion of check valves and the Tigerloop™ product at OIL TANK PRESSURE for alternatives to conversion of a single line to a two line oil supply piping system.
OIL LINE LEAKS - Oil Line leaks found - can lead to oil heat system puffback and loss of heat
Watch out: leaks in heating oil appliance piping or filters can be much more serious than just a drip spot on the floor. The same leak that allows oil to drip out of the oil filter or piping connections allows air to be drawn into the system when the oil fuel unit (oil pump for the water heater, oil fired boile or furnace) is running. That air leak into the system results in improper oil burner operation, soot clogging, and even a loud bang at oil burner start-up or worse, a dangerous puffback.
Example of inspection report where leaks or drips are found in heating oil piping:
Caution: we saw a possible oil line leak:
... wet oily sections of piping at
... oil stains on the floor at
...
Oil leaks may be hazardous and also, as air may be drawn into the oil line when
the fuel unit is pumping, they can lead to improper system operation and even
loss of heat in the building.
It may come as a surprise but drawing air into the oil burner from a leak in the oil line can leave an air bubble in the oil burner nozzle. When the oil burner shuts down the pressure inside the nozzle area drops from 100 psi or more down to ambient pressure of just a few pounds.
The reduction in pressure causes that little air bubble to expand, pushing extra oil out of the oil burner nozzle where it dribbles into the oil heating system boiler or furnace combustion chamber. The next time the oil burner starts-up this un-burned oil residue forms a mini explosion - you may hear a sort of "bang" when the oil burner starts. This malfunction can lead to a serious puff back blowing soot into the home, or worse. This is an unsafe condition caused by what looks like a tiny innocent drip such as the one we show in our photo above.
This item should be checked/corrected by your
service person promptly.
SINGLE HEATING OIL LINE on a BURIED HEATING OIL TANK - Single oil line on buried oil tank risks lost prime, no heat
A single oil line was found coming from tank to oil burner.
Recommended practice is use of two pipes, for several reasons: avoiding loss of
prime, providing alternate pipe if supply pipe clogs, and reducing the lift
load on the pump.
Note: some experts recommend that the fire-safety valve for these systems be
installed ONLY on the supply line, with only a simple check valve on the
return line. This procedure reduces the risk of burst gasket at the oil pump
and spray of heating oil into an existing fire should a valve on the return
line close before the valve on the supply line during a fire.
DUAL HEATING FUEL OIL LINE - improper installation of oil line shutoff valves
On oil fired heating equipment systems that use an open loop oil piping system or dual oil line piping arrangement (such as used with buried oil tanks and at other installations where the oil burner fuel unit may otherwise lack adequate lift and pumping capacity), the fusible-link type heating oil line shutoff/safety valve should be located only on the oil supply line at the oil burner.
Do not install a second fusible-link fire safety valve (OSV) shutoff-valve on the return oil line. Use a check valve instead. Details are at DUAL OIL LINE 2 VALVES
OIL LINE SHUTOFF VALVE - missing or improper location
The proper location for the oil line shutoff valve with a fusible link (Fire-o-Matic™ type valves) is just before the oil filter and close to each individual oil burner. Details about oil line valve installation and operation are at OIL LINE SAFETY VALVES.
HEAT TAPE HAZARD - Heat Tapes on Heating Oil Piping May Be a Fire Hazard
As we cited at OIL TANK INSPECTION REPORTS, outside above ground heating oil storage tanks in cold climates are exposed to jelling of the heating fuel. On these systems the oil piping is sometimes fitted with
a heating tape in an attempt to avoid freeze-up in the oil line itself. This is a potential fire hazard.
Heat tapes should not be used on heating oil lines.
Safety Recommendation: unless the heating tape is specifically designed for the purpose and is protected against short circuits, do not use electric heat tapes to keep fuel oil lines from
plugging during cold weather. Such measures are an obvious fire hazard.
Watch out: as we explain at Heat Tape Guide, some models of heat tapes used for freeze protection can cause a building fire if the tapes are not installed according to the manufacturer's recommendations, particularly if the tape crosses over itself.
As Ryan Duffy points out, connecting the heat tape to a GFCI-protected circuit can substantially reduce the risk of heat tape fires. However if the GFCI-protected heat tape circuit trips-off during typical current leakage conditions and without drawing attention of the building occupants, the risk of freeze damaged piping, leaks, water damage, and mold damage will be increased.
The US CPSC recommended in 1994 that HUD consider dropping its no-GFCI-on-Heat-Tape-Circuit provision, and that heat tape powering electrical circuits be be protected with a GFCI device in the electrical panel rather than at the electrical receptacle or "outlet". Ground fault protection was first required in the 1987 NEC for heat tapes that did not have a metal covering. In 1996/1999 the NEC expanded the requirements for GFCI protection and specified that mobile homes would have at least one heat tape receptacle. [A significant number of heat tape-related fires occurred in mobile and manufactured homes.]
Pipe insulation to prevent freezing is discussed at Pipe Insulation.
Steps to prevent freezing building drains and traps are discussed at Drain Pipe Protection.
HEATING OIL FILTER - NONE - No Oil Filter Installed on Oil Fired Equipment
If we do not find a heating oil filter installed on the system this is a defect that risks loss of heat.
Most modern oil heating equipment will have an oil filter installed, such as the one shown in our photo at left.
Notice that there's a heating oil leak below the connection to the filter outlet? This leak will suck air into the oil burner when it's running, leading to improper and possibly unsafe operation, risking a puffback.
Unless you find or the owner can point out a filter already in place, we recommend
installation of one - to be located at or very near the burner and "downstream"
of a fire-o-matic safety shutoff valve to permit easy service. Failure to
provide adequate filtering may lead to loss of heat and subsequent damage to
the building.
Frequently Asked Questions (FAQs) about troubleshooting & clogged or leaky heating oil appliance piping & oil piping connections
Question: how to get the heating oil line flowing after hurricane & flood damage
I am having problems restarting the water heater ever since hurricane irene slammed into New Jersey and my basement flooded. We changed the motor and oil fiter, but are having problems getting oil to feed through the lines I was wondering if there were suggestions. - Antoinette
Reply: Guide to How to clear or un-block a clogged heating oil line by CO2 blasting, filter changeout, or oil line replacement
Antionette,
When an oil fired water heater has been flooded, such as by hurricane Irene, there are a number of concerns that need to be addressed. You have taken two obvious steps by changing parts (motor and oil filter) but I can add a few suggestions that might help:
Oil lines can become blocked with sludge, silt, mud, even water if the lines are open to the flooding environment. Normally an oil line between the oil tank and oil burner, say at a water heater, is always full of fuel oil, and sealed against oil leaks out and air leaks in to the piping system. So dirt or water from outside the system would not easily enter the piping system.
But if the oil tank itself were flooded you might have water and mud or silt and dirt on the tank bottom - if your oil line feeds from the tank bottom all of that crud would enter the oil line. So a further check of the condition of the oil tank is in order.
A buried oil tank should, like the oil piping, be sealed against outside water entry (though in times of area flooding a partially empty oil tank might float-up and break lines or cause leaks).
An above ground oil tank should be ok IF flood waters never rose high enough to enter the oil tank vent or fill piping.
If your oil tank itself checks out as not contaminated with water and dirt, and provided we are sure that the oil burner assembly was itself entirely replaced and that the oil pump (fuel unit) is working properly, and if you are unable to draw oil from the tank, the usual step employed by the service tech is to use a CO2 gas cartridge and special "gun" assembly that connects to the oil line and attempts to "blow out" an obstruction. If you are unable to make the line usable following that procedure, and provided we remain convinced that the line is the culprit, I'd have the service company run a new fuel line between the oil tank and the burner.
I'd also be sure the service tech was following proper procedure for bleeding air out of the oil piping during service restoration.
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Additional technical contributors & reference sources for this article are listed below.
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[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.
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
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