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Rheem gas fired water heater (C) InspectApedia.comGuide to Gas-fired Hot Water Heaters
Inspection, Diagnosis, & Repair

Gas water heater guide:

How to buy, install, inspect, troubleshoot & repair gas-fired hot water heaters.

The articles at this website will answer most questions about all types of hot water heaters as well as many other building plumbing system inspection or defect topics.

LP & Natural Gas-fueled calorifiers, hot water cylinders, water heaters. 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.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

Inspection, Diagnostic, & Repair Guide to Gas-Fueled Hot Water Heaters

Schematic of a gas fired water heater (C) Carson Dunlop AssociatesHow do we Identify a Natural Gas or LP Gas-fired Water Heater?

The sketch at left shows the basic components of a gas-fired water heater and is provided courtesy of Carson Dunlop Associates, a Toronto home inspection, education & report writing tool company [ carsondunlop.com ]. It's easy to identify a gas-fired water heater:

if you can find your water heater tank at all, take a look at what pipes and wires are connected to it.

A gas-fired water heater will have two water pipes connected to it (cold-in and hot out), and a pipe or in some jurisdictions a flexible copper tube bringing LP gas or natural gas to the heater.

The gas fired water heater will have a flue or "chimney" which vents combustion gases outside, either by connection to an existing chimney or flue, or in the case of power-vented and high efficiency gas water heaters, flue gases may be vented outdoors by a plastic pipe.

You'll also see a thermostat and gas valve control which combines a temperature setting with a safety device that senses the presence of a gas flame. (If there is no flame the control will turn off the flow of gas to the appliance.) Lots of newer gas fired water heaters will also include a flue gas spill switch at the draft hood atop the water heater.

Caution: sometimes an electric or other additional 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 besides the first water heater that you see.

Other hot water sources, such as a TANKLESS COIL for making domestic hot water may also be present.

Gas-fired water heater Inspection Checklist

Gas Fired Water Heater (Calorifier, Cylinder, Geyser) Inspection Point

Gas Water Heater Hazard Details in This Article

More Information

Chimneys & Vents

Missing draft hood, blocked chimney, flue or vent, rusted or leaky flue or vent, short flue, short chimney, cold flue, shared flue with improper vent into chimney, backdrafting, flue gas spillage, blocked draft hood

Dangerous Carbon Monoxide Hazards such as venting of a water heater alone into an old masonry chimney

BACKDRAFTING HEATING EQUIPMENT

DRAFT REGULATORS / HOODS GAS HEATERS

GAS FIRED WATER HEATER VENTING CODES

GAS FIRED WATER HEATER CHIMNEY & VENTING DEFECTS - topic home

Burner & Burner Flame

GAS FIRED WATER HEATER FLAME DEFECTS

such as flame rollout, burn marks, improper flame color, uneven flame, noises, flame lift off burner

GAS FLAME & NOISE DEFECTS

GAS IGNITER DIAGNOSIS & REPAIR

Combustion Air Supply

INADEQUATE COMBUSTION AIR AT GAS WATER HEATERS

due to location in an enclosed space or where combustion air intake is blocked

COMBUSTION AIR REQUIREMENTS

COMBUSTION AIR for TIGHT BUILDINGS

Temperature & Pressure Relief Valve

GAS WATER HEATER RELIEF VALVE HAZARDS

such as improper or missing TPR valve piping, TPR valve leaks, or TPR valve inaccessible

BLEVE boiling liquid vapor explosion

RELIEF VALVE, WATER HEATER

RELIEF VALVE LEAKS

TUNDISH used in PLUMBING

WATER HAMMER NOISE DIAGNOSE & CURE

Installation Location & Position

such as located in a bedroom, installed horizontally

GAS WATER HEATER INSTALLATION LOCATION, POSITION, MECHANICAL DAMAGE
Leaks at or around the Water Heater

& other leaks such as a leak at the TPR valve or at nearby water supply piping.

LEAKY WATER HEATER TANKS

RELIEF VALVE LEAKS

Temperature Settings for Water Heater

Water heater temperature settings

may be too high: a scalding burn hazard, or too low, water is not hot enough.

ANTI SCALD VALVES & TEMPERATURE CONTROL / MIXING VALVES

GAS HOT WATER TEMPERATURE CONTROL - how to set

HOT WATER IMPROVEMENTS

WATER HEATER TEMPERATURE TOO LOW

SCALDING TEMPERATURES & TIMES

Piping & Controls

Piping materials, routing, such as leaks in the gas piping, use of plastic piping too close to the water heater, improper stop valve locations, corroded leaky piping or piping connections

FLEXIBLE GAS CONNECTOR INSTALL

GAS LEAK DETECTION, LP / NG

WATER HEATER CONTROLS, PIPING VALVES

WATER HEATERS for HOME HEATING USE?

Insulation

CHECK GAS WATER HEATER INSULATION

- add-on insulation is usually unnecessary and may be dangerous

INSULATE HOT WATER TANK?

Dip Tube / Sacrificial Anode

SACRIFICIAL ANODE & DIP TUBE OF THE WATER HEATER TANK

a failed dip tube causes loss of hot water while a corroded sacrificial anode can cause odors in the hot water supply

ANODES & DIP TUBES on WATER HEATERS

Noises at the Water Heater Water heater noises are often traced to the lime scale deposits on the water heater bottom or to water hammer (that can also cause TPR valve leaks)

WATER HAMMER NOISE DIAGNOSE & CURE

WATER HEATER DEBRIS FLUSH

WATER HEATER NOISE DIAGNOSIS, CURE

WATER HEATER SCALE DE-LIMING PROCEDURE

Odors in Hot Water Supply Water heater odors or odors in hot water, particularly sulphur or rotten egg smells are often traced to a bad sacrificial anode

ODORS IN WATER

WATER ODOR DIAGNOSIS - SULPHUR

Old or Antiquated Water Heaters

ANTIQUATED & ANTIQUE GAS FIRED WATER HEATERS

may be unreliable or unsafe

RANGE BOILER WATER HEATER

Pilot Light OFF

Assure the gas supply is working, turned on, not leaking

Re-light the standing pilot

For heaters using a standing pilot, the control provides means to ignite the pilot flame; some gas fueled heating equipment use a spark igniter or a hot surface igniter instead of a standing pilot.

GAS BURNER PILOT LIGHT PROCEDURE

GAS PILOT WON'T STAY LIT

GAS IGNITER DIAGNOSIS & REPAIR

Improper LPG <-> Natural Gas Fuel Conversion

To convert a gas fired water heater or any gas appliance between fuels requires changes to the regulator, gas orifices, and other adjustments.

Otherwise the equipment will not operate properly and is unsafe.

GAS CONVERSION LP / Natural Gas

Water Heater Safety: other concerns  

WATER HEATER SAFETY

Water Heater Exposed to Freezing  

WINTERIZE A BUILDING

Notes to the table above

Caution: no inspection checklist for any topic can ever be complete or comprehensive; important water heater inspection topics may be omitted as we're working on this section.

If you have comments, questions, suggestions, Contact Us by email.

Synonyms for "water heater" vary depending on where you live and include calorifier, hot water cylinder, geyser. The inspection points for gas water heating devices listed in this table apply equally to calorifiers, hot water cylinders and geysers.

Gas Water Heaters, Control Valves & Thermostat Manuals

Honeywell gas water heater control valve WT8840B1500/U cited & discussed at InspectApedia.com

Rheem PROTEC natural gas water heater control cited & discussed at InspectApedia.com

Rheem natural gas water heater thermostat & gas control valve AP14270G cited & discussed at InspectApedia.com

Robertshaw Unitrol Gas Water Heater Valve R110R Unitrol - at InspectApedia.com ... Water heater gas valve Robertshaw 91602 - cited & discussedat Inspectapedia.com

Below: Robertshaw 91602 Gas Control. This gas valve replaces Robertshaw AT91601 and is used on gas heaters that employ a pilot flame, Pilot Model Series: G4SM; G6A; G6A-2; G6A-3; G6A-6; G6A-6P; G6A-7; G6A-7P; GC10-1; G10-2; G10-2P; GC6A; GC6A-3; GC6A-6; GC6A-7; GC6AA-7P; GC6AA-A8; GC6AA-8P; GC10-2; GC10-2P; GC10A-2.

Robergshaw 110-series Gas Control Valve & Thermostat for water heaters - cited & discussed at InspectApedia.com ...Robergshaw 110-series Gas Control Valve & Thermostat for water heaters - cited & discussed at InspectApedia.com

 

Gas Water Heater Flame Defects

Solid gas flame at the burner of a Cal-o-Rex glass lined LP gas water heater in Pozos, Guanajuato, Mexico. The flame dispersing cone is damaged. (C) Daniel Friedman (2015)

Check for flame color indicating inadequate combustion air, damaged gas burners, gas flame roll-out burn marks, dirty or obstructed gas burner orifices, uneven flames.

See GAS FLAME & NOISE DEFECTS for details

Inadequate Combustion Air at Gas Water Heaters

Check for proper combustion air supply for your gas fired water heater.

Failure to provide sufficient combustion air is dangerous: lack of adequate combustion air will cause a gas burner to produce dangerous, potentially fatal carbon monoxide gas.

Gas Water Heater Relief Valve Hazards

Check 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 details also at RELIEF VALVES - TP VALVES

Gas Water Heater Installation Location, Position, Mechanical Damage

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.

Leaky water heater tanks & other leaks

Leaks at a hot water heater (C) Daniel Friedman

In our photo at above left a gas-fired water heater is leaking.

That puddle on the floor needs investigation. Look for leaks at valves and piping around the water heater, leaks in the water heater tank itself, and look for leaks at the pressure/temperature relief valve.

Check the settings of the Gas Water Heater Control Temperature settings

Gas water heater control and thermostat (C) Daniel Friedman

Watch out: Water heater temperatures set above 120F risk scalding the building occupants unless a mixing valve or anti-scald valve system has been installed.

See details at GAS HOT WATER TEMPERATURE CONTROL - instructions for setting the temperature control on gas fired water heaters

For a water heater temperature set too low, providing water that is not hot enough.

see WATER HEATER TEMPERATURE TOO LOW.

On a gas fired water heater the heater temperature control is usually on the gas valve itself - the black dial shown in the photo above..

See ANTI_SCALD VALVES & HOT WATER QUANTITY for details about safe hot water temperatures.

Check Gas Water Heater Piping, Valves, Controls

Improper water heater control valve installation (C) Daniel FriedmanCheck the 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 (blue arrow in our photo at left)..

There should be no shutoff valve installed on the hot water line (red arrow in our photo) leaving the water tank.

Check for Gas Leaks: In addition to a characteristic odor that you may smell associated with LP or natural gas leaks, a prolonged gas leak may leave telltale dark stains on the gas piping or control.

See GAS LEAK DETECTION, LP / NG for details.

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.

See this Carson Dunlop sketch of a vacuum relief valve [image].

Plastic piping used for hot water distribution & connected to a water heater

Leaks at a hot water heater (C) Daniel Friedman

In our photo above a gas-fired water heater is connected to plastic water supply piping. The pressure rating of plastic water piping systems is usually specified in terms of the temperature as well as pressure in the piping system.

Watch out: hot water temperatures may reduce the permitted pressure rating of plastic water piping in some installations, depending on the brand and product type of plastic water piping installed.

The risk is a burst water pipe, scalding, or flooding in the building.

On some plastic water piping systems you may also find a hot water expansion relief valve installed to provide added protection to the system.

An expansion tank or additional pressure/temperature relief valves can prevent these problems and may also extend the life of the water heater. Details are

at HOT WATER EXPANSION TANKS

and at HOT WATER EXPANSION VALVES

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

Corrosion & leaks at water heater piping & connections

Corrosion & leaks at water heater piping & connections (C) Daniel Friedman

Our photo above shows corrosion at dissimilar metals at the top of a water heater tank. When the connections at the water heater top are sufficiently rusted and corroded the heater will be un-repairable.

Check Gas Water Heater Insulation

Look for insulation that has been improperly added to the water heater tank - it may be unsafe and may violate the manufacturer's installation instructions and warranty.

See INSULATE HOT WATER TANK?

Antiquated & Antique Gas Fired Water Heaters

Just below we show a still-working Standard Combination Gas FIred Boiler / Water Heater manufactured by Keystone Supply in Philadelphia, PA. I think this water heater is more than 80 years old.

Gas water heater control and thermostat (C) Daniel Friedman

The antique wall-mounted gas-fired water heater shown below is installed in the Gaudi Apartments in Barcelona, Spain.

Gas fired water heater, antique Barcelona Spain Gaudi Apartments (C) Daniel Friedman

By modern standards this is an unsafe water heater, venting directly to the indoor space. I suspect that originally it vented outdoors.

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

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

The dip tube on many water heaters 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 hot water tank from early failure due to corrosion.

Here Carson Dunlop Associates' sketch shows the location of the sacrificial anode on an electric water heater.

If your water supply happens to be highly conductive or corrosive

see WATER TESTING GUIDE for details

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.

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

Check the Gas-fired Hot Water Tank Temperature and Pressure Safety Relief Valve

Please see TESTING the Water Heater Temperature Pressure RELIEF VALVE

Gas Fired Water Heater Chimney & Venting Defects

LP Gas water heater fire (C) Daniel Friedman Gogorron San Luis Potosi MexicoThis discussion has moved

to GAS FIRED WATER HEATER CHIMNEY & VENTING DEFECTS - topic home

where we include a discussion

of GAS FIRED WATER HEATERS VENTING & COMBUSTION AIR HAZARDS

Our photo shows an LP gas fired water heater that caught fire. This outdoor water heater installation was observed at the Ex Hacienda, Gogorron, San Luis Potosi, Mexico.

The complete absence of a venting chimney on this heater may have been a factor in its poor operation.

The water heater inspection dog was a volunteer.

Check for proper exhaust venting of combustion products from your gas fired water heater (calorifier, geyser, hot water cylinder).

See also

 




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Reader Comments, Questions & Answers About The Article Above

Below you will find questions and answers previously posted on this page at its page bottom reader comment box.

Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2021-02-18 - by (mod) -

So the frozen point is somewhere in the common cold-in to the water heater or in the hot-out from the water heater before it branches off to all of those various locations.

Take a look at the suggestions at PIPE FREEZE-UP POINTS https://inspectapedia.com/plumbing/Pipe_Freeze_Points.php

and then grab a hair dryer and see if you can thaw the freeze-point; when you find it you'll know where you need to add a heat source and fix cold drafts so as to avoid having the problem over and over.

On 2021-02-17 by Yvette

0° weather cold water is working and running fine and flowing fine. Hot water line in all faucets tub in bathroom bathroom sinks kitchen sinks the hot water line is not flowing at all. I have a gas water heater and the gas is on.

On 2021-01-06 - by (mod) -

Justin Heck said:

I drained a water heater at my mothers house that was over 30 years old and had never been cleaned. it was over 1/3 of the way full of black goop. The sediment had built up so much i ended up replacing the Unit. Proper Maintenance would have prevented this.

On 2020-06-18 - by (mod) -

Willie

Please forgive the delay in my answer, I have been in an area where new internet was available.

Let's start by inspecting every Plumbing connection above or near the top of the water heater and also the temperature pressure relief valve connection on the side of the water heater.

If any of those is leaking water could be running down inside the jacket of the water heater and out at the bottom. If you are absolutely confident that there are no plumbing leaks into the heater body or insulation jacket that it sounds to me as if the unit is defective and needs to be replaced under warranty

On 2020-06-10 by Willie Roberts

new water heater leaking from the bottom

On 2018-11-27 - by (mod) -

Jose

Qual forma de calentador usas: electrico, gas?

Si es electrico, cheque primero al panel por luz.

On 2018-11-27 by Jose

Mi calentador de agua dejo de trabajar. como si se hubiera apagado de repente. como trato de solucionarlo.


...

Continue reading  at GAS FIRED WATER HEATER CHIMNEY & VENTING DEFECTS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see GAS FIRED WATER HEATER FAQs - questions & answers about gas water heaters, cylinders, calorifiers, posted originally on this page

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