Gas Water Heater Installation
Step-by-Step Guide
(updated 2018)

Find out how to install a gas water heater properly using the provided step-by-step guide and easy to use instructions. See what is the best location for the large cylinder, what are the venting and plumbing requirements, what tools are needed, and how to avoid problems.

During the gas water heater installation, state and local codes and manufacturer instructions must be followed, to ensure reliable and safe operation. One of them, for example, is an installation of the expansion tank on the incoming water supply line and in a closed heating system. Some codes also require a special license to connect gas line to your heater, vacuum relief valve, venting regulations and more.

Gas water heater installation is not an easy DIY job and can be really costly, if not done correctly. For the proper installation and worry-free operation, you have to have some knowledge and experience to deal with the electricity, plumbing, and gas, including the building codes.

And if you are not comfortable doing such a work, contact a professional plumber.

Required tools

Either you are replacing an old or installing a new gas water heater, most of the required tools are found in almost any handyman home, and these include:

  • Adjustable plumbing wrenches
  • Power drill
  • Pipe cutter
  • Screwdriver
  • Garden hose for draining
  • Plumbing sealant or tape
  • Also: pipes, fittings, valves

Choosing the right location for a gas water heater

Before installing a gas water heater you should carefully choose an indoor location as its placement is very important for the safety of the occupants, economical and efficient use of a unit. Keep in mind that the tank-type water heaters, as opposed to tankless, can only be installed indoors.

Your gas water heater should not be installed in the area where gas or water leakage from the water heating system can damage adjacent areas and lower floors and cause the damage to the structure.

The risk of the water and gas leak, difficulties to maintain, service, handle, remove and control, are the reasons why some plumbers do not recommend attic installation, even knowing that some homes (especially those with the slab foundation), already have it installed.

To ensure the proper water and gas flow, the floor, where the unit will be standing, must be on a level surface. Certain local codes might require a stand to raise a heater and provide a required clearance.

That is the reason why it is important to provide the right drainage solution under the water heater, like drain line or drain pans. Since the burner and air inlet are located in the lower part of the tank your drainage solution must not restrict this entrance.

The selected location must provide an adequate clearance for servicing and maintenance. Do not put the tank directly on the carpet, but if you have to, put the piece of metal or wood panel beneath.

During gas water heater installation, keep in mind that combustible and flammable products, like paint, propane, gasoline, should never be stored in the same room or close to this unit. Most modern water heaters are equipped with the FVIR system, which ensures that there will be no ignition of the flammable vapors outside the combustion chamber.

In order to reduce the energy waste and in a case if the water line is too long, insulate the pipes to protect them from exposure to the freezing temperatures. You can always wrap the heater with an insulated jacket or blanket and reduce the standby loss. Or before you install the unit, make sure, if possible, to place it close to the most used application and power source.

Install your tank-type gas water heater only in the designated room, but not in bathroom, bedrooms or any unprotected outdoor location. You will want to place your water heater close to the external wall to make a room for the vent pipes. This is why garages, laundry rooms, and basements are good spots.

Venting requirements

Install your gas water heater close to the external wall to ensure an unobstructed venting, short vent pipe run and sufficient fresh air for normal operation.

When planning to install a gas water heater in the confined space, two openings have to be made for sufficient combustion and ventilation air intake. One opening is located within 12" above the floor and the other 12" from the ceiling. The total free area of the opening depends on heater's BTU.

Check also are the vent connectors properly secured, flue baffle installed in the flue tube, connected to the chimney or vent pipe system, and at a safe distance from other combustible materials. Also supported with the metal hanger on a specified distance. Do not operate the unit if the flue baffle is not installed. The manufacturer instructions must be followed.

Note: Venting requirements, either dealing with the power vented, direct vent or atmospheric water heaters are dictated by the building code. It is required to install a unit per code and with the potential problem that might arise, it is recommended to contact a professional technician.

If the vent kit is supplied with the water heater it must be installed per manufacturer's instructions, such as following the minimum rise, termination setup, sealing the vent kit joints, proper clearances and other.

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Installing an atmospheric type water heater

Atmospheric water heater from Bradford WhiteBradford White

The vent pipes of the atmospheric type water heaters must provide an upward, natural movement of the hot air. The flue gases moved by the natural draft, are directed from the combustion chamber through the draft diverter, metal vent pipe, chimney and outdoors. If the house does not have a chimney or similar, using this type of the heater can be expensive to install.

Proper venting depends on the pressure difference between the highest and lowest point on the vents including the surrounding air pressure. Any obstruction leads to back drafting, gas spillage and exposure to carbon monoxide.

For the natural draft type water heater, it is recommended to use a galvanized steel pipe or preferably B-vent (double wall vent pipe), secured to the draft hood with sheet metal screws. The size is usually 3" or 4", depending on the unit capacity.

The problem with the single wall vent pipe is that it might cause an excessive condensation if used in colder areas (garage for example).

For the proper draft, the metal pipe between the heater and chimney must run upwards rising not less than 0.25" per foot and should be straight and as short as possible.

The surrounding air, which enters the house from the outside, is used for gas combustion and dilution. If the house is tightly sealed, this can lead to a problem as there will be no sufficient air coming in - other venting option should be considered.

Installing a power-vented water heater

Power-vent water heater from RheemRheem PV

As opposed to atmospheric type water heaters, power-vented (PV) models, also known as an induced draft or fan-assisted, can have the venting pipes installed either horizontally through the side wall or vertically through the roof.

This is because PV models use the electric blower (fan) and dedicated vent pipes, usually made of PVC. The blower, which is mounted on top of the unit, guarantees proper venting and eliminates the risk of the negative pressure buildup inside the home.

PV water heaters are often found on energy efficient models and are recommended for homes without a chimney or where it is hard to install atmospheric type. But, they are more expensive.

Installing a direct-vented water heater

Rheem DV water heaterRheem DV

Direct vent water heaters (DV) also rely on the natural draft for proper venting. This type is great for homes with no chimney and no electric source located close to the unit. The advantage is that you will have hot water even if the power goes out.

DV models are designed with a single or dual vent pipe system. Single-vent models use the surrounding air for combustion and one vent pipe to move the exhaust gases outside the building.

Dual-vent models utilize two pipes, where one pipe is used to draw the fresh air from the outside, while the other pipe is used as an exhaust.

As the air coming from the outdoor, DV models do not have a problem with the insufficient indoor ventilation.

How to check proper venting

Use this test to check is there a proper venting on your gas water heater (atmospheric):

  • Make sure all the windows and doors are closed and the unit is running.
  • Take the extinguished match and put it near the vent hood.
  • If the venting system is operating correctly, the smoke from the match should pull into the vent hood. If it blows back, there is a problem. This issue must be fixed as soon as possible as there is a risk of carbon monoxide poisoning.

Connections and things to consider

Make sure the electrical, gas and water supply are turned off, on the electrical panel, shutoff valve and gas control valve.

Drain the water heater.

Remove the vent pipe, if replacing the old model.

Only when the gas and water supply are connected, preferable by a licensed plumber, the tank can be filled. When the air is removed from the water heating system, the gas supply can be activated and tested for leaks. Never use hot water heater unless it is completely full of water.

For the valid warranty, the reliable and safe operation of the water heater, the installation must be performed by a licensed technician.

Connecting the gas line - Tips

  • Check, is the gas type and pressure supplied to the heater the same as indicated on the rating plate. If it is not, contact the gas supplier.
  • A manual shut-off valve must be installed in the gas supply line and close to the water heater.
  • The gas regulator, control valve, has a 1/2" female threaded connection, which is typical for most gas hot water heaters.
  • After you are done with the gas water heater installation, always check connections for the leak. Use a solution of a dish-washing soap and water and apply to the gas pipe connections. A leak will cause the soap to bubble. If there is a leak, tighten the loose connection, and check again.
  • Per building codes, drip leg or sediment trap should be installed to collect any small particles or moisture that are present in the gas pipeline.
  • A union must be installed between the gas control valve and shutoff valve, for easy maintenance.

Connecting gas piping to the control valve of the heater can be accomplished by either flexible connector or black iron pipe.

Connecting plumbing line tips

Plumbing work includes connecting your home plumbing and the cold water inlet and hot water outlet (3/4" N.P.T male thread) including the following elements:

  • Dip tube installed in the cold water inlet
  • Shut-off valve
  • Union installation so the water heater can be easily disconnected if needed
  • Temperature and pressure relief valve installation, including the discharge line
  • Check valve and pressure reducing valve, if needed
  • Expansion tank

The following instructions are based on the assumption that an old water heater has to be replaced.

If your home plumbing uses the galvanized pipes, remove the pipe close to the water heater and at the nearest fitting.

If it uses copper or plastic pipes simply cut the pipe close to the water heater, using the pipe cutter.

To make a connection between the water heater and plumbing you have several options; hard or flexible connections. Flexible is better especially when the existing pipes do not line up with the new heater connections. And it is faster to put it on. But first, check the codes.

In order to make the hard connections, you will need more than basic skills and the right fittings to line up the pipes, while with the copper pipes there will be some cutting and soldering.

With the plastic pipes, it is even easier, using the right fittings and sealants where needed. Just keep the plastic pipes at least 6 inches away from the hot surfaces.

Final notes

All the information about gas water heater installation you have found here is only for your reference. Our recommendation is to contact licensed installer or plumber, as the legal codes, regulation and manufacturer's instructions have to be followed. And remember safety first.

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Tankless water heater installation
Tankless installation tips
Installing a gas water heater
How to install an electric water heater

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