Heater Handbook Plain guidance for the water heater in your house.

Start with the heater you already have

By Heater Handbook editorial team · November 1, 2026 · 6 min read

Heater Handbook is a plain-language guide to tank, tankless, gas, electric, and heat pump water heaters, from symptoms and maintenance to sizing and cost.

The heater in the closet is a tank, a burner or a heat pump, and a short list of parts that fail in known ways. Heater Handbook is the book for that list. It tells a sweating tank from a split one, a pilot that will not stay lit from a lockout you should stop resetting, and a cheap quote from a quote that forgot the vent. It is a little dry on purpose. Hot water is not a lifestyle.

This is an editorial site, not a contractor. Nothing here turns on a gas valve, sizes a flue, or opens an electrical panel for you. Where a step is reasonable for a careful homeowner, the guide says so and names the hazard. Where the next move is a licensed plumber, gas fitter, or electrician, the guide stops. The disclaimer is the short version of that rule. The editorial policy is how the pages are sourced.

What is in the house

Most homes in the United States still have a storage tank: a steel vessel, glass-lined, with a burner or electric elements keeping forty to eighty gallons hot all day. Some have a tankless heater that fires only when water moves. A growing number have a heat pump water heater, which is still a tank, but the heat comes from the room air instead of a resistance element. A few have a condensing gas tank, a point-of-use heater under a sink, or a tank heated by a boiler. The types section separates those machines so a troubleshooting step meant for a standing pilot is not applied to a power-vented condensing unit.

The useful label on a storage heater is not the gallon number painted on the spec sheet. It is the first-hour rating: how much hot water the full tank can deliver in a busy hour, recovery included. Tankless heaters are sized by flow in gallons per minute at a temperature rise, and that rise changes with the season because groundwater does. Both methods are written out with the Department of Energy worksheet in the buying section. If you are choosing rather than repairing, the decision pages are tank or tankless, electric tank or heat pump, tankless or heat pump, and heat pump rebates in 2026. The federal tax credit people still print on bids ended for equipment placed in service after December 31, 2025.

Route by what you notice

Start with the symptom, not with a replacement quote.

  • No hot water at all from a gas tank, including a unit that clicks and never stays lit: gas diagnosis and, if you can see a standing pilot, pilot will not stay lit.
  • No hot water from an electric tank, or the high-limit button has tripped: electric diagnosis. If the breaker opens again as soon as you reset it, stop and use breaker keeps tripping.
  • Hot water that fades in one shower: runs out too fast. That is a different failure from a tank that never heats.
  • Water on the floor: leaks, fittings, and condensation. A wet jacket is not automatically a dead tank, and a dead tank is not a parts job.
  • Popping, rumbling, ticking, or a tankless whistle: noises.
  • Rotten eggs at the hot tap only: smell. A gas odor in the room is not that article. Leave and call the gas utility.
  • Rust, milkiness, or grit: discolored water.
  • A tankless code, a cold sandwich, or hot water that only fails in January: tankless symptoms.
  • A temperature-and-pressure valve that weeps: why it drips. How to test one, and why some manufacturers would rather you did not, is in testing the relief valve.

If the symptom is a carbon monoxide alarm, a gas smell, scorched wiring, or water coming from the steel of the tank itself, do not work down a list. Shut the fuel or the breaker if you can do that without delay, stop using the heater, and follow when to call a pro.

Maintenance that changes the life of the tank

Scale and a spent anode rod shorten a storage tank more reliably than age alone. Flushing moves sediment out the drain valve. The anode is a metal rod that corrodes instead of the steel. The relief valve is the last device that can dump pressure or temperature if a control fails. Those three jobs are written as procedures, with the points where people crack a plastic drain valve or dry-fire an electric element: flush a tank, anode rods, and test the relief valve.

Tankless heaters need a different afternoon. Scale inside the heat exchanger is removed with a small pump and a food-grade acid, usually vinegar, through service valves. That procedure is descaling. Whether you are on well water at fifteen grains of hardness or a city supply at three changes how often either job is due. The chemistry and the softener interaction are in hard water and scale.

The maintenance section puts those jobs on a year, including the heat-pump filter, which is not a tank flush and not optional.

Buying, money, and the label

A replacement quote is three numbers wearing one coat: the heater, the labor and materials to put it in legally, and the operating cost after that. Equipment prices quoted from a website omit the gas line, the new vent, the electrical circuit, the pan, the expansion tank, the permit, and haul-away. Published installed ranges from HomeAdvisor, Angi, and ENERGY STAR are collected in what water heaters cost, labeled as ranges with the year of the source. They are not a bid.

The federal Energy Efficient Home Improvement Credit that covered qualifying heat pump water heaters does not apply to equipment placed in service after December 31, 2025. That is an IRS rule, not a retailer talking point, and it is written up in the cost guide so a 2026 bid is not shaved by a credit that has ended. State and utility rebates are separate and local.

How long the new unit should last, and when a repair is the better spend, are separate questions. Lifespan uses the Department of Energy's published service lives and then lists what knocks a tank off that curve. Repair or replace is a decision from the leak, the age, and the quote, not from a slogan. Uniform energy factor explains the yellow EnergyGuide label, including why a gas UEF and an electric UEF are not a single ladder.

Gas heaters need combustion air and a vent that actually drafts. Electric heaters are a 240-volt continuous load. Stored water hot enough to control bacteria is hot enough to scald a child in seconds. The safety section covers venting and carbon monoxide, temperature, permits and seismic straps, electrical work, and the boundary of a homeowner's job.

If you only remember one measurement, make it the temperature at a tap after a long run, taken with a thermometer, not the story the dial tells. The Consumer Product Safety Commission’s tap-water scald guidance is the source for the burn times used in temperature, scalds, and Legionella.

How to use a page

Each guide states what the job of that page is, then the steps or the comparison, then the point where a licensed person takes over. Tables are there to be used, not to decorate a heading. Sources sit at the bottom as real documents: Department of Energy, ENERGY STAR, the CPSC scald publication, IRS credit pages, ICC code notes, and manufacturer documentation. If a manual for your model disagrees with a general step here, the manual wins. Send the correction to the address on the contact page.