How to clean & restart flooded heating equipment or restore a flooded water heater to service:
This article describes procedures for inspection and repair of flooded heating appliances: flooded heating boilers, furnaces, and water heaters. We include post-flood start-up procedures for air conditioners, air handlers, heating boilers, furnaces, and water heaters.
Area flooding due to storms or building flooding due to a fire or burst water pipe can leave heating appliances inoperative as well as unsafe to use unless adequate inspection, cleaning, and repair or replacement of certain parts are made.
Different depths of flooding have different implications for inspection & repair of heating appliances after hurricanes, rising flood waters, burst pipe leaks, of sewer backups. We describe recommended safety checks, inspections, & repairs for flood-damaged water heaters, boilers & furnaces. Our page top photos shows a client pointing to the level reached by flood waters in a building basement - the heating boiler, water heater, and other basement appliances had been inundated with muddy water from area flooding.
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This article describes air conditioning & heating system components that you need to inspect, clean, repair or replace after the equipment has been partially or completely flooded or otherwise damaged by a flood or other disaster.
For each component we explain what needs to be done to safely return the component and the system to safe reliable operation to provide building heat or hot water.
We include links to articles giving further details about cleaning, troubleshooting, or repair if needed.
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 filter, but are having problems getting oil to feed through the lines I was wondering if there were suggestions. - Antoinette
When an oil fired water heater has been flooded, such as by hurricane Irene that flooded the Northeastern U.S. in August 2011, there are a number of concerns that need to be addressed.
Before addressing flooded water heaters, boilers, or furnaces, if your building has been flooded, see FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP for advice about priorities of entry, diagnosis & repair of homes or other buildings after flooding from any cause.
CMHC provides this nice summary statement, for which we provide actual how-to details in this article:
If they have been soaked, consult an HVAC (Heating,Ventilation and Air Conditioning) contractor to replace the furnace blower motor, switches and controls, insulation and filters.
Inspect all flooded forced air heating ducts and return-duct pans and have them cleaned out or replaced. Seek advice from your local utility about a water heater that has been wet. Refrigerators and freezers may need to be replaced. 
Now to the flooded water heater: you report having taken two important post-flood steps by changing parts (motor and oil filter) but below we have listed suggestions that might help get the water heater (or a flooded heating boiler or furnace) running again and also assure its safety and forward life.
The extent of disassembly, inspection, and replacement of parts of any heating appliance (water heater, furnace, boiler) after building flooding depends on the height reached by floodwaters and perhaps also the duration of flooding.
Our flood damage photo at the top of this page shows our client pointing to flood water markings on the heating system expansion tank - water had nearly filled the basement of this home - the heating boiler had been completely under water. Our oil fired water heater sketch (left, - Courtesy Carson Dunlop Associates, used with permission) shows the internals of that appliance and illustrates what gets wet at different flood water levels.
Certainly any water heater, boiler,or furnace component that was under-water or soaked needs to be inspected, and as appropriate, cleaned or replaced. On the other hand, basement flooding that did not even reach the level of the oil burner assembly may have left that component intact, but still may have entered and damaged the heating appliance combustion chamber.
We list and describe procedures for every post-flood inspection and repair point for air conditioner air handlers, boilers, furnaces, and water heaters in the text below.
The level of cleaning, repair or replacement of a flooded air handler used for air conditioning or warm air heating depends on the depth to which the unit was flooded and on just what components have become wet or flooded.
If the heating equipment was exposed to just a wet floor or even an inch of water it may be possible to quickly return the system to operation.
But if the heating equipment was soaked (such as during extinguishment of a fire) or flooded (by rising floodwaters) then its safety controls, motors, switches, combustion chamber and other components that were wet or flooded will need cleaning, repair, or replacement, as we will describe below.
For detailed assistance with heating or cooling equipment that won't run after you've cleaned and replaced parts, see these articles:
The sketch at left illustrates basic parts of a conventional gas fired warm air heating furnace; image courtesy of Carson Dunlop Associates.
The level of cleaning, repair or replacement of a flooded air handler used for air conditioning or warm air heating depends on the depth to which the unit was flooded and on just what components have become wet or flooded. We discuss gas burners or oil burners separately below.
Our photo (above right) shows that the oil fired heating boiler was flooded enough to place all of the oil burner key parts under at least some water - this system should not be operated before it is cleaned and restored by an expert.
Our photo (above left) provides two heating equipment flooding observations
For detailed assistance see these articles:
Safety controls (see below) and insulation in heating equipment are usually replaced after flooding or other wetting disaster events like hurricanes or storms.
Inspect the heating piping, baseboards, or radiators for leaks or mechanical damage, especially if there is any evidence of movement of or in the building.
If hot water heating system pipes were drained or if pipes broke and lost water, you will need to purge air from the system and to check circulator pump(s) and zone valves (if used);
If pumps or valves or control relays were submerged most heating service professionals will replace controls and will dry and test electric motors before returning them to service.
See AIRBOUND HEAT SYSTEM REPAIR by WATER FEED VALVE for assistance with purging air out of heating piping, baseboards, or radiators.
A cracked, plugged, or leaky chimney can cause fires or carbon monoxide poisoning.
Be sure you check metal and brick chimneys for cracks, damage, signs of movement, as well as for obstructions by dirt, debris. Also check for visible gaps, or leaks before lighting the furnace or a fire.
In addition, a thorough inspection of the combustion chamber for damage and debris must be conducted before the equipment is returned to service. Mud, sludge, debris anywhere inside of the heating appliance (combustion chamber, heat exchanger, chimneys, flues) has to be removed and the appliance cleaned. In addition, if area flooding sent flood waters inside of chimneys or flues (don't forget the chimney base and cleanout door) those areas need to be opened, inspected, cleaned.
Most oil fired heating equipment use a masonry (fire brick) or synethetic fabric combustion chamber liner. The liner heats to very hot during oil burner operation - a condition that helps assure complete combustion of fuel oil being sprayed into the combustion chamber.
Watch out: Firing up a flooded oil fired heating appliance before the combustion chamber liner has been dried or replaced risks damaging that component and possibly damaging the heater itself. Ask your service technician about the condition of the combustion chamber.
Heating appliance (water heater, boiler, furnace) safety and limit switches and controls that have been flooded, in our OPINION, should be replaced. These include controls such as an aquastat, cad cell relay, stack relay, or fan limit control switch.
Circulator pump relays, while not safety devices themselves, may be inoperable after flooding without disassembly, dryout and cleaning - a procedure that may cost more than the cost to replace the control. Other electrical components such as electrical wiring may be re-usable after inspection.
Watch out: electrical panels and circuit breakers that have been flooded should be replaced as even if they "look" fine, we're not confident that internal working parts have not been damaged by water, corrosion, or even silt and debris. The risk is that a flooded circuit breaker has become mechanically damaged or corroded internally such that it may not trip properly in response to an overcurrent or short circuit that may occur when you are restoring power to the building or later in the future. The risk is thus a shock or fire.
The inspection points listed above pertain to oil fired heating devices that have been exposed to flooding or sewer backups. In addition, for building heating systems, the heat distribution system may also have been flooded, damaged, or require repairs and cleaning.
If the gas has been turned off at the main valve serving your home, you need to have a professional restore gas service to your home, relight pilot lights, and do a final check of the system.
If the gas valve serving only one appliance is turned off, then you can probably turn gas service back on, check for leaks, and then relight that appliance.
First, make sure the room is well-ventilated (open windows & doors to outside) and that there are no open flames anywhere. Then turn on the gas valve. Check for leaky pipes. Let the gas run for a minute or two to clean any air and impurities out of the pipes. Then turn the gas off for a minute to allow the gas in the air to go away before you light the appliance.
Watch out: if you smell gas, do not turn on or off electric switches, use a telephone or cell phone, nor use any other equipment or control that can create even the smallest spark. Doing so risks a catastrophic gas explosion.
For detailed assistance see these articles
Propane, LP gas, or butane fuels are kept in pressurized tanks, so there is no electric pump to turn on, and provided that the tank was not empty, no flood water would be expected to enter the tank.
Watch out: check the gas tanks for signs of movement or floating. If the tank has moved at all from its original position, inspect the gas piping for loose or damaged connections, and repair them before attempting to turn on the gas.
Then follow the instructions above for gas systems.
In the reader question above s/he said that the "motor" was replaced. If you are not sure whether just the electric motor on the oil burner was replaced or whether the whole oil burner assembly was replaced,
see OIL BURNERS for an illustration of the different parts involved. If the oil burner was submerged, and if only the oil burner's driving electric motor was replaced, additional disassembly and cleaning are probably in order to be sure that the oil burner nozzle, blower assembly, and other parts are clean and working properly.
Make sure your main oil valve is turned off. Check your heating oil oil pump and oil burner assembly. If it got wet, have the oil burner and pump professionally checked and cleaned. If you want to clean it yourself, keep in mind that you will need replacement parts like oil burner nozzle, fuel unit screen, oil filter cartridge, and a clean heating oil supply ready to use when bleeding air and water from the system.
Look carefully for any signs of leaking oil; if you see any, call a professional. Look for signs that the pipes or oil tank moved during the flood. Oil tanks, even buried ones, will float when flooded. After you have turned the electricity back on, open the main valve and turn the pump on. Check for leaky pipes.
The amount of cleaning and parts replacement necessary for a heating system depends on the depth of flooding to which the equipment was exposed. A heating boiler or furnace whose oil or gas burner was not submerged may be got running with a careful cleaning and inspection of the combustion chamber and (if hot air heat) duct system, and chimney. But if the oil or gas burner was flooded it will need to be disassembled, cleaned, some controls and parts replaced, and tested.
Watch out: Rather than risk the fire or safety hazards that ensue if a heating system safety control is not reliable, heating professionals will generally replace any heating system control (like an aquastat, cad cell relay, stack relay) that has been soaked or submerged.
This article continues to list all of the major components of oil fired heating equipment and how they should be cleaned, inspected, repaired or replaced after a flood or other disaster.
For detailed assistance with oil burner inspection, cleaning, repairs see:
It makes sense to replace an oil filter cartridge after a building has been flooded; the cartridge canister is normally air tight and thus water tight. But repair steps, movement of equipment, or other events may have contaminated the canister itself or oil tank or piping, sending more debris into the canister and filter. For this reason it makes sense to not just replace the filter, but inspect and clean the canister that holds the filter.
Remove the oil filter cartridge and replace it; we don't recommend operating the heating equipment without a cartridge and filter in place because of the high probability of debris clogging that will occur in the oil pump or oil burner nozzle. Remove any water found in the oil filter canister as well as sludge or debris before you replace the oil filter with a new one.
Debris, sludge, water, rust particles are often found in the bottom of the oil filter canister. If these enter the oil burner's oil pump (properly, the fuel unit), its internal filter screen may also be clogged - I'd be sure that the fuel unit has had its filter screen replaced.
Debris in the oil burner fuel unit will clog its internal check valves and the oil burner nozzle too, damaging the pump and leading to improper, even unsafe oil burner operation or total loss of heat later on. Also a clogged filter screen can prevent the fuel unit from being able to pump oil from the tank - and could be mistaken for a blocked oil line.
If oil piping has become contaminated with sludge, it may be possible to blow the lines clear, but if not, oil line replacement will be needed unless the piping has been broken, kinked or mechanically damaged (as can occur if flooding cause an oil tank to float or move).
Oil lines between an oil tank and the water heater can become blocked with sludge, silt, mud, and even water or sewage if the lines are open to the flooding environment. If you have this problem, when the oil burner motor runs (the oil fuel unit is trying to pump oil) and you try to bleed air from the oil piping system you will find that no fuel is flowing from the oil tank to the burner motor.
But 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.
Also be sure the service tech was following proper procedure for bleeding air out of the oil piping during service restoration. Details are at How to bleed air out of oil piping and oil burner fuel units.
So how might debris enter and clog oil piping after a building flood? 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).
Watch out: if a buried oil tank or even an above ground oil storage tank was not sufficiently full of oil during area flooding the tank may have floated up out of the ground or off of its (above ground oil tank) supports. The result of such movement will be bent, damaged oil piping, possibly leaks and an oil spill, and water and debris may have entered the oil storage tank. See
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.
A fusible link oil piping shutoff valve should be found at the oil burner (just before the oil filter) and perhaps also at the oil storage tank. A valve at the oil tank is often used for service convenience if the oil piping exits at the tank bottom. If oil piping or the oil tank were open to floodwaters debris often collects right at the control valve.
See FIRE SAFETY CONTROLS for a discussion of oil piping fire safety valves.
this important safety device should be flushed and tested as per the manufacturer's instructions. Dirt or debris in the relief valve interior could prevent its proper operation or, more often, it can cause the valve to leak if it has not been adequately cleaned.
See these detailed articles on relief valves
Most heating appliances (water heaters, furnaces, boilers) include an insulated outer jacket or "skin" that helps keep heat and noise inside the device and that improve its operation.
If the insulation on a flooded appliance is still wet when the appliance is turned back on you might get lucky and dry it out during the next operating cycle. Or equipment might be damaged, or the insulation might need replacement. Ask your service technician about the condition of the appliance insulating jacket.
Watch out: flood waters in a disaster often contain sewage and other pathogens that can enter and contaminate any kind of building or appliance insulation. You might, at least temporarily, take a chance on using an appliance like a water heater whose insulation was partly wet, but floodwater contaminated insulation in equipment like an air handler or inside of duct work that is made of or lined with fiberglass insulation is unsanitary.
Blowing air from an air conditioner or heater into a building through pathogen-contaminated ductwork or air handlers is unsanitary and risks illness or disease. Such components should be replaced.
To get a water heater working after flood, hurricane, earthquake or other disaster damage the steps needed depend on the type of heater that you have installed.
Most likely in all cases of tank type water heaters you'll want to drain and possibly sanitize the tank along with building water supply piping as well as flush and test (or replace) the pressure / temperature relief valve and discharge tube.
For gas or oil fired heaters, see the fuel and burner inspection and restoration procedures listed in this article. For other types of hot water equipment see or home page at x or see
For additional water heater inspection & cleaning procedures also see
Here Carson Dunlop's sketch shows the location of the sacrificial anode on an electric water heater. 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. For details of how to inspect or replace the sacrificial anode or dip-tube on a water heater, please see Water Heater Anodes & Dip Tubes or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.
This article series 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.
Continue reading at OIL TANK WATER REMOVAL or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.
Or see BUILDING DAMAGE ASSESSMENT & REPAIR - home
Or see FLOOD DAMAGE CLEANUP & REPAIR GUIDE - home
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(May 12, 2015) Gunther said:
Can a gas hot water Boiler be fixed after immersion by a flood
Not to be glib, anything can be fixed. The question is whether or not there is damage beyond economical repair. The answer depends on just what got flooded. It's common to replace just lower portions, for example a burner and controls, that got flooded - often the boiler itself can be salvaged. In sum as Florida expert Mark Cramer says ... It Depends.
A professional inspecting the boiler for flood damage will see how deep the water came, what components were under water, and what components need to be repaired or replaced. If the total of those repairs approach the cost of a new boiler then it's new boiler time.
But often a flood of just a few inches on the floor or even flooding that covered the oil burner or gas burner does not destroy the boiler itself nor the controls and components that were mounted high enough to stay out of the water and that remained dry. In that case, particuarly if the boiler is cast iron, it's likely to be salvageable after a complete cleanout, replacing the combustion chamber liner and replacing the burner and any other controls that were soaked.
Watch out: even if the heater will "run" after having been flooded it may not be safe to use without inspection, repair, and perhaps replacement of any controls that were wet. A safety control that has been wet may become corroded internally such that later it will fail to do its job.
(Dec 26, 2014) xMargie said:
My electric furnnace is flooded and won't riun what can ido
Watch out: Leave the system off. It is dangerous to turn on flooded electrical components or fuel burners before the whole system has been inspected or repaired as needed. Turn off electric power to the heater at the electric panel.
Watch out: don't even try to touch the electric panel or any other electrical devices or switches if your home is still flooded, wet, or if you are staning in water.
When we've faced this problem before, rather than turn on flooded and unsafe equipment we borrowed or rented portable heaters to help dry out the building or to provide needed heat.
(Dec 5, 2014) Surrey Furnace Repair said
Thanks author for your useful site and great shared to Plumbing Service. WOW !! Really awesome blog and information. I got valuable info here about Repairs for Heating Systems.
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