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WATER HEATERS
ALTERNATIVE HOT WATER SOURCES
  High Efficiency Water Heaters
  Indirect-fired Water Heaters
  Instantaneous Water Heaters
  Multiple water heaters in parallel
  Multiple water heaters in series
  Range Boiler Water Heaters
  Side Arm Coil Water Heaters
  Solar Water Heaters
  Tankless Coil for Hot Water
ANTI SCALD VALVES
CHIMNEY INSPECTION DIAGNOSIS REPAIR
Clogged Piping & Hot Water Flow
ELECTRIC WATER HEATERS
GAS FIRED WATER HEATERS
  DRAFT HOODS - gas fired
  Gas BTUH & Cubic Feet
  GAS PIPING, VALVES, CONTROLS
  SPILL SWITCHES - Flue Gas Detection
HOT WATER IMPROVEMENTS
HOT WATER QUANTITY IMPROVEMENT
  Alternative Hot Water Sources & Methods
  Anti-Scald Valves & Hot Water Quantity
  Clogged Piping & Hot Water Flow
  Extra Tanks to Increase Hot Water
  Insulate Hot Water Piping
  Insulate Hot Water Tank?
  Larger Diameter Water Supply Piping
  Tankless Coil Hot Water Increase
  Temperature of Hot Water is Too Low
INDIRECT FIRED WATER HEATERS
ODORS IN WATER
OIL FIRED WATER HEATERS
  DRAFT REGULATORS - barometric dampers
  OIL BURNERS
  OIL BURNER NOISE SMOKE ODORS
  OIL PIPING
  OIL TANKS
MIXING VALVES
RANGE BOILERS
RELIEF VALVES - TP Valves
SEWER GAS ODORS
SOLAR HOT WATER HEATERS
TANKLESS COILS
  Clogged Piping / Tankless Coil & Hot Water Flow
  Mixing Valves
  Tankless Coil Leaks
  Tankless Coil Hot Water Increase
WATER HEATER PROPERTIES
  Electric, Gas, Oil Water Heater Efficiency
  Water Heater Life Expectancy Comparisons
  Water Heater Operating Cost Comparisons
  Water Heater Purchase & Maintenance Costs
  Water Heater Water Quantity Comparisons
  Water Heater Recovery Speed Comparisons
  Water Heater Safety Comparisons

BOILERS, HEATING
CARBON MONOXIDE/DIOXIDE
FURNACES, HEATING
HEATING SYSTEMS
HOT WATER SUPPLY
NO HEAT - BOILER / FURNACE DIAGNOSIS
PLASTIC HEATER VENT
PLUMBING
SAFETY DURING HEATING INSPECTION


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Oil fired water heater with a backpressure sooting problem (C) Daniel FriedmanGuide to Oil-Fired Hot Water Heaters - Inspection, Diagnosis, & Repair
PlumbingAPedia ©

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  • Oil fired Hot Water heaters: how to inspect, test, adjust, repair
  • How to choose among types of hot water heaters
  • Guide to inspection of electric water heaters
  • No Hot water? how to get more hot water flow, quantity, performance from your water heater
Our site offers impartial, unbiased advice without conflicts of interest. We will block advertisements which we discover or readers inform us are associated with bad business practices, false-advertising, or junk science. Our contact info is at inspect-ny.com/appointment.htm.

This collection of articles on oil hot water heat will answer most questions about oil-fired water heaters as well as many other building plumbing system inspection or defect topics. This page contains links to in-depth articles on inspecting, testing, and repairing problems residential hot water heaters of all types, including their parts, controls, and alternative sources for hot water as well as tips for improving hot water temperature, hot water pressure, and hot water quantity. Reproduction of this web page electronically at other websites is prohibited. Our photo at page top shows an oil fired hot water system with the main components easily available, and with evidence of an oil burner operating problem.

© Copyright 2008 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left.

Inspection, Diagnostic, & Repair Guide to Electric Hot Water Heaters

How do we identify an oil-fired water heater?

Schematic of an oil fired water heater (C) Carson DunlopThe sketch at left shows the basic components of an oil-fired residential hot water heater and is provided courtesy of Carson Dunlop. It's easy to identify an oil-fired water heater:

  • An oil burner will be mounted (usually) near the bottom of the hot water tank, fed by home heating oil from a local above ground or buried oil tank. See OIL BURNERS and OIL BURNER NOISE SMOKE ODORS
  • A flue vent connector or "stack pipe" will leave the top or upper rear side of the water tank and continue on into a chimney (or directly outside if your water heater is a "direct-vent" or "power vent" system. See CHIMNEY INSPECTION DIAGNOSIS REPAIR and see DRAFT REGULATORS - barometric dampers.
  • Two water pipes will be connected to the water heater: cold-water in, and hot water out. The hot water tank shutoff valve is normally installed only on the cold water supply line.
  • A pressure and temperature relief valve should be installed right on the water heater, coming off of the tank top or upper area of its side. See Relief Valves - TP Valves for details.

But watch out: sometimes an electric water heater is installed as an additional or backup hot water source, so you'll also want to see if you have other hot water heating equipment installed, such as a Tankless Coil for Hot Water. In our photo below at left an oil-fired water heater and an indirect-fired water heater are installed in tandem.

Here are a few things to check on your oil-fired water heater:

(WARNING: This is an INCOMPLE LIST and important water heater inspection topics may be omitted as we're working on this section. If you have comments, questions, suggestions, Contact Us.)

Leaks at a hot water heater (C) Daniel FriedmanCheck the pressure and temperature relief valve on your water heater: look for evidence of corrosion, leaks, improper installation, etc. A missing, modified, blocked, or leaky pressure relief valve is extremely dangerous and can lead to a catastrophic BLEVE boiling liquid vapor explosion that can cause severe damage or even fatalities at a building. See Relief Valves - TP Valves

Look for evidence of leaks in the hot water tank, or mechanical damage, or improper installation. For example most water heaters are intended to be installed in a vertical position. Installing a hot water tank horizontally or in a hole in a crawl space is likely to cause early failure of the heater, violate the manufacturer's guidelines, and may be dangerous.

In our photo at left that puddle on the floor needs investigation.

Look for the draft regulator/barometric damper. If your conventional oil fired water heater does not have its own, personal draft regulator installed, it is impossible for the heater to have been tuned for optimum performance - you may be wasting money and heating oil. See DRAFT REGULATORS - barometric dampers

Check the settings of the water heater temperature: See Temperature of Hot Water is Too Low

Look for insulation that has been improperly added to the water tank - it may be unsafe. See Insulate Hot Water Tank?

Oil fired hot water heater showing visible signs of improper, possibly unsafe operation (C) Daniel FriedmanLook for signs of improper oil burner operation: such as sooting, draft problems, or back-pressure burns around the oil burner or around the combustion chamber inspection port.

Soot blowing out of the barometric damper or flue pipe, soot and burn marks, oil leaks, stumbling, rumbling, noisy oil burners, odors, are examples of improper oil burner operation that need prompt service.

Our page top photo and our photo at left show examples of improper oil burner operation on an oil fired water heater: both systems show soot blow-out at the water heater's combustion chamber inspection port. Our photo at left also shows that the discharge tube is missing from the relief valve - a safety concern.

Often these soot marks are a symptom of excessive pressure or "back pressure" inside the combustion chamber.

This problem can be caused by an oil fired water heater that is way past due for cleaning (soot blocks the exhaust flue), by a blocked chimney, by improper draft regulator adjustment, or other defects.

See OIL BURNERS and OIL BURNER NOISE SMOKE ODORS

Check the hot water piping and control valves connected to the water heater for leaks, support, and for proper location of shutoff valves. An improperly installed shutoff valve on a water heater can be very dangerous, risking an explosion. Usually the "hot water tank shutoff valve" is installed only on the cold water pipe coming into the water tank. There should be no shutoff valve installed on the hot water line leaving the water tank.

Check for leaks at the water heater drain valve. Most water heater manufacturers recommend that their water tank be drained periodically. This process will help remove sludge and debris or mineral deposits that may have accumulated at the bottom of the water heater tank. Removing this debris can extend the life of the hot water tank, especially where electric and gas fired water heaters are involved. But since few people remember to open and drain the tank it may be that the drain valve does not open easily, or worse, it won't close.

  • Tips On Draining the Water Heater Tank: Don't try opening the hot water tank drain valve without first noting these warnings and tips:
    • The water heater heat source should be turned off and the water tank cooled down (or run hot water out through building fixtures) before attempting to drain the tank - there can be a serious scalding hazard otherwise
    • You can connect a garden hose to drain the water heater tank to a suitable destination
    • If it's a Sunday - you may have trouble obtaining spare parts or emergency plumbing service if a problem occurs
    • Be sure to have a spare garden hose cap to install over the end of the drain valve in case it drips and won't shut off completely
    • If you have trouble turning the water heater tank drain valve to open it - don't force it - if break off the valve stem you may have a leak that you cannot shut off except by turning off cold water supply to the water heater
    • After opening the heater drain valve, if you forgot to turn off the cold water supply coming into the water heater, you may find that water just shoots out of the drain forever - you'll need to turn off the cold water supply to the water heater.
    • You will probably need to open a nearby hot water tap to let air into the plumbing system and through it into the water heater tank so that water can drain out at the tank's bottom. We don't recommend opening the pressure/temperature relief valve for this purpose as you may find that the TP valve won't shut successfully afterwards.

Check for heating oil leaks and oil piping defects: see OIL TANK PIPING DEFECTS

If plastic water piping is installed, such as polybutylene water supply piping, it should be at least 18" from the water heater.

Vacuum relief valves are required at water heaters in some communities, to protect against collapse of the water storage tank and to prevent backup of hot water into the cold water piping should cold water pressure drop. Here is Carson Dunlop's sketch of a vacuum relief valve.

Oil Fired Water Heater Controls & Operation

The principal controls on an oil fired water heater include the following water tank and oil burner parts and controls:

  • BOILER CONTROLS & SWITCHES (many controls on oil fired heating boilers are the same on oil fired water heaters)
  • Aquastat Functions - simple aquastats may be used as upper and lower limit controls on oil fired water heaters
  • Cad Cell Relay Switch Flame Sensors - turns off the oil burner if it does not achieve proper flame ignition
  • Circulator Pumps & Relays - may be used if the water heater is connected to a continuous hot water loop plumbing system or in (more rare) cases where an oil fired water heater is being used as a building area heating device (usually not code-approved)
  • Limit Switches, Boilers simple aquastats may be used as upper and lower limit controls on oil fired water heaters
  • Mixing Valves - used to permit keeping the water heater at high temperature (more total hot water will be available) without risking scalding the building occupants
  • Relief Valves - TP Valves - required on every pressurized tank, including oil fired water heaters
  • Stack Relay Switch - an older safety switch used to turn off the oil burner if successful burner flame ignition does not occur

Check the Sacrificial Anode & Dip Tube of Your Water Heater Tank

Schematic of a sacrificial anode on a hot water tank (C) Carson Dunlop

At Temperature of Hot Water is Too Low we explained that a leaky dip tube in a water tank can result in hot water temperatures that are too low.

But the dip tube on many water heaters also functions as a sacrificial anode, as we show here. By constructing the dip tube of a metal which is more readily corroded than the steel of a steel hot water tank, the anode protects the tank from early failure due to corrosion. Here Carson Dunlop's sketch shows the location of the sacrificial anode on an electric water heater.

If your water supply happens to be corrosive (see WATER TESTING GUIDE) then the dip tub/sacrificial anode in the water tank may indeed corrode away until it leaks (dropping the hot water temperature) or disappears entirely.

It's a relatively small plumbing job to disconnect water pipes from the water heater and then pull and check, and replace the dip tube/sacrificial anode if necessary.

If your hot water smells like rotten eggs, you should definitely check the condition of the sacrificial anode on the hot water heater, no matter what kind of water tank you've got installed.

The articles listed below describe the inspection, operation, diagnosis, repair, and improvement of each type of water heater, and we include detailed advice about how to improve hot water supply in buildings as well as inspection and correction of leaks, high hot water costs, odors, noises, and safety problems.

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.

Technical Reviewers & References

Particular thanks are due to experts and also consumers who read these articles and suggest corrections, changes, and additions to the material. Content suggestions, technical corrections and content critique are invited for any of the content at our website.

  • Daniel Friedman - principal author/editor of the InspectAPedia TM Website
  • Thanks to Alan Carson and Bob Dunlop, Carson Dunlop, Associates, Toronto, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education, publications, report writing materials, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
  • Critique, contributions wanted: Contact Us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.

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PLUMBING TOPICS
HEATING SYSTEMS
WATER HEATERS
ALTERNATIVE HOT WATER SOURCES
WATER HEATER PROPERTIES
ANTI SCALD VALVES
CHIMNEY INSPECTION DIAGNOSIS REPAIR
Clogged Piping & Hot Water Flow
ELECTRIC WATER HEATERS
GAS FIRED WATER HEATERS
HOT WATER IMPROVEMENTS
HOT WATER QUANTITY IMPROVEMENT
INDIRECT FIRED WATER HEATERS
ODORS IN WATER
OIL FIRED WATER HEATERS
MIXING VALVES
OIL & GAS PIPING
GAS PIPING, VALVES, CONTROLS
OIL TANKS
RANGE BOILERS
RELIEF VALVES - TP Valves
SEWER GAS ODORS
SOLAR HOT WATER HEATERS
TANKLESS COILS
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