Gas Water Heater Installation Instructions

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Gas water heater installation instructions. Step-by-step guide how to install a gas water heater properly, including tank-type water heaters from Rheem, Bradford White, AO Smith, Reliance, Kenmore, GE, American and other manufacturers.

In order to provide years of the safe and trouble-free service, installing a gas water heater should be done by the professional plumber or HVAC technician and in accordance with the codes.

When installing a gas water heater, the manufacturer's instructions should be read carefully as the improper set up may result in low heater performance, lack of hot water, shorter unit life, property damage and health hazard.

Tools required

For the correct gas water heater installation one should consider using the following tools:

  • Pipe wrench

  • Screwdriver

  • Drill

  • Teflon tape or pipe sealer

  • Hacksaw for cutting the copper pipes or tubing cutter

  • Propane tank and the torch

  • Tools for sweat soldering; soft solder, wire brush...

  • Expansion tank

  • Metal drain

How to install a gas water heater

Prior to installation, always inspect all the components inside the heater's box, for possible damage. If something looks suspicious call the manufacturer and the technical support.


Safely done gas water heater installation complies with the codes and manufacturer instructions. Correct installation will eliminate possible carbon monoxide poisoning and fires, flooding, electric hazard and other problems.

Every tank type heater should be installed indoors in the vertical position, vent outside and protected from freezing. Location where the new gas water heater has to be put is especially important if the tank is leaking, for some reason. This is why an attic and the upper floors are not advisable. The recommendation is to install a gas water heater in the location with the drainage, as close to the vent terminal and where it will provide an easy access to operate and service the unit.

Avoid installing the heater directly on the carpet - use a metal or wood panel underneath the heater. Under every water heater, a suitable drain pan should be installed and piped to an adequate drain. Do not install the gas water heater in bedrooms, bathrooms or other small and closed rooms where lack of air supply might affect the clean and safe combustion.

Proper clearances from the combustible material should be given. Due to fire and explosion hazard never store flammable materials close to the heater.

For mobile and manufactured homes use a gas water heater that is designed for such applications.

TPR valve

In the process of gas water heater installation it is very important to have a listed temperature and pressure relief valve installed (it should be factory provided) and as the safety device. The TPR valve prevents any damage to the tank from the excessive temperature and pressure. From the TPR valve, there should be a tube piped to within 6" of the drain, which should not be plugged or capped – no obstructions.

Installing the expansion tank

If the gas water heater is installed in the closed water systems install the thermal expansion tank on the cold water supply, so it can lower the temperature and pressure if they increase significantly inside the system.

Shut off valve is "must" in front of the unit so you can easily install the gas heater, troubleshoot and do the repairs. The mixing valve is recommended to prevent scalding water, especially if kids are around.

Installing the venting system

Make sure that there is enough fresh air inside the room where the heater is installed. If the gas hot water heater is installed in the confined space, two permanent openings should be provided on the certain distance from the floor and top of the enclosure. The size of the opening depends on the total BTU of the unit. If the gas unit is installed in the unconfined (open) space, the air inside the room is enough for correct gas combustion.

Fresh air must be provided to the gas water heater so the flame can burn clean with the blue color. The air must enter the combustion chamber from below the unit and enter the flue vent below the draft hood - for the atmospheric vent models. It is important not to block these areas, such as using the insulation blanket. The exhaust vent has to be terminated outside of the building, made of the recommended material and properly sized.

Flue baffle has to be positioned in the flue tube, and vent connectors properly sized and securely fastened with screws. Avoid unnecessary bends, dips or sags.

Recommendations and tips

  • Read the rating plate found on the gas heater. Provided labels have useful information such as a guide for lighting the pilot light, the type of the gas, the power, etc.

  • Install the manual gas shut-off valve so gas delivery to the heater can be stopped anytime in a case of the failure or emergency.

  • Install the drip leg.

  • Install a ground joint union between the shut-off valve and gas valve.

  • Test all connections for gas leaks with the soap-water solution.

  • Use dielectric unions or couplings when connecting a water heater to a copper pipe.

  • Shut off valve should be installed in the cold water inlet pipe.

  • Install the pressure reducing valve if water pressure is above the maximum allowed.

Notes for the safe gas water heater installation:

  • Never run the water heater if it is not filled with water.

  • Do not operate your gas water heater if flood damaged.

  • Do not remove stickers and labels found on the outside surface of the water heater, there is some very useful info there.

How to maintain a water heater

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