Water heater installation: what to know

What the job involves, what changes the price, and what to ask a pro.

What water heater installation is

Water heater installation replaces or adds a tank water heater, including the venting, gas or electric hookup, the expansion tank and any code upgrades the new unit triggers. People call when the old heater has failed, is leaking, or is past the age where repairs make sense.

Signs you need it

  • Water is leaking from the tank body itself and not from a fitting or valve, which means the tank has failed and repair will not fix it
  • Rust-colored water or a rumbling noise from the tank that gets worse as the tank heats
  • Hot water runs out much faster than it used to, with heavy sediment in the tank
  • The old heater has no expansion tank, no drain pan, or a T and P relief valve that drips or has been capped
  • The vent no longer meets what a new unit of the size you want needs, or the fuel type has to change

What the pro does

  • Shut off the gas or power and the water supply, then drain the old tank and disconnect the gas or electric line and the vent
  • Check the venting path and the combustion air supply, since a new unit often needs a different vent size or a power vent
  • Set the new tank on a level base with a drain pan, and connect the cold and hot lines with flexible connectors or pipe as the install requires
  • Install an expansion tank on the cold line when a check valve or pressure reducer makes the system closed
  • Connect the T and P relief valve and run its discharge pipe to a safe drain point, with no valve on that pipe
  • Light the gas unit or energize the electric elements, check the flame or element, and test for leaks at every joint

What changes the price

Every job is different, so we do not publish prices. These are the things that move the quote up or down.

  • Fuel type and whether the gas line, electrical circuit or venting has to be changed
  • Tank size and whether the heater must fit a tight closet, attic or garage space
  • Venting: a new vent run, a power vent, or a change from a metal to a plastic vent system
  • Whether a drain pan, expansion tank, T and P valve or pressure reducing valve must be added to meet the install
  • Access to the old and new location, including stairs or tight corners
  • Permit and inspection requirements in the area, and whether a seismic or wall strap is needed

What a written quote should spell out

  • Brand, model, tank size, fuel type and the recovery rate of the new unit
  • Venting work, including any new vent pipe, its material and the connection points
  • Expansion tank, T and P valve, drain pan and discharge line, and whether each is new
  • Gas or electrical work included, and whether it is done by the plumber or a licensed electrician or gas fitter
  • Disposal of the old tank and whether the warranty is registered for you

Questions to ask before you hire

  • Is the new unit sized for the number of people and the peak use in the house?
  • Does the venting need to change, and how will you check draft and combustion air after the install?
  • Will you add an expansion tank, and why do you think the system needs one?
  • Where does the T and P discharge pipe end, and is it run to a safe place?
  • Who pulls the permit and calls for the inspection?
  • Does the warranty depend on the installer, and will you register it?

Red flags

  • Pro who reuses an old vent or a cracked vent section without checking it
  • Pro who blocks, caps, or plugs the T and P discharge line, or puts a valve on it
  • Pro who skips the expansion tank on a closed system with a check valve or pressure reducer
  • Pro who does not check the gas connection for leaks with a proper test

What you can do yourself

A homeowner can clear the area, move the old unit to make room, and confirm the new unit's model and fuel type before the install. Do not handle gas lines, venting or the electrical circuit yourself, since a wrong vent connection can release carbon monoxide and a bad gas joint can leak.

Licenses and permits

Water heater installation is commonly licensed work, and gas or venting work often requires its own license or a licensed gas fitter. Many areas also require a permit and inspection, so check with your state or local licensing agency.

Water heater installation questions

Do I need an expansion tank?

If the water system has a check valve, a pressure reducing valve or a backflow device, the water has nowhere to go when it heats and expands. An expansion tank gives it somewhere to go. Ask the pro to explain why one is or is not needed for your system.

What is a T and P relief valve, and why does it matter?

The temperature and pressure relief valve opens if the tank gets too hot or the pressure gets too high. Its discharge pipe must run to a safe place and cannot be capped. A valve that drips or is blocked is a safety fault.

Can I replace a gas water heater with an electric one?

Yes, but it means taking the gas line and venting out of use, adding an electrical circuit sized for the new heater, and checking the space for the new unit. Get both the gas and electrical scope in writing before the install.

How long does a new water heater take to install?

A straight swap in an open space often takes part of a day. Venting changes, new circuits, or a new gas line can add time, and the pro should give you a window before work starts.

About this guide

This national guide is written and checked by infinibell. Rules and conditions differ by place, so local pros are credited on guides for the cities they serve, not on national ones.

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