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Guide · Hot water

Water heater guide: tank vs. tankless, gas vs. electric

How water heaters work, the safety parts that matter, signs of trouble, and how to choose a replacement for a New York or New Jersey home.

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01How a tank water heater works

Cold water enters the tank, a gas burner or electric elements heat it, and hot water leaves from the top. A thermostat controls temperature. The temperature and pressure (T&P) relief valve opens if temperature or pressure gets too high; its discharge pipe must never be capped.

Typical gas water heater connectionsDiagram D5
  • Cold water
  • Hot water
Typical gas tank water heater connections A tank water heater with a cold-water inlet and shutoff valve, a thermal expansion tank on the cold side where required, a hot-water outlet, a temperature and pressure relief valve with a discharge pipe ending near the floor, a drain valve at the bottom, and a gas supply with a shutoff valve and sediment trap. The flue vent rises from the top. Requirements vary by code and model. flue vent expansion tank T&P relief valvedischarge pipe ends near floor drain valve gas supply + shutoffsediment trap 123456
  1. 1Cold-water inlet with shutoff valve
  2. 2Thermal expansion tank (where required, e.g. with a check valve or pressure regulator)
  3. 3Hot-water outlet to fixtures
  4. 4Temperature & pressure (T&P) relief valve and discharge pipe: never cap or plug it
  5. 5Drain valve for flushing sediment
  6. 6Gas supply with shutoff and sediment trap: gas work is for licensed professionals only

02Types compared

Water heater types
TypeGood forConsider
Gas tankMost houses with gas; fast recoveryNeeds proper venting; tank takes space
Electric tankNo gas service; simple installSlower recovery; higher operating cost in many areas
Tankless (gas)Continuous hot water; saves spaceOften needs larger gas line and new venting
Heat pump (electric)EfficiencyNeeds space and air volume; cools the room
Indirect / boiler coilHomes with a boilerTied to the boiler's operation

03Signs of trouble

  • Water at the base of the tank: usually a corroded tank
  • Dripping from the relief valve pipe
  • Rusty hot water
  • Popping or rumbling (sediment)
  • Hot water running out faster than before

04Choosing a replacement

  • Size it to your household's peak use, not just the old tank's size
  • Check gas line capacity and venting for tankless or high-efficiency units
  • Ask about expansion tanks where required
  • Expect a permit and inspection in most NJ towns; in NYC, use a Licensed Master Plumber

Tankless heaters mount on the wall and heat water on demand.

05Frequently asked questions

Can I replace a water heater myself?

In NYC, no: plumbing and gas work must be done by or under a Licensed Master Plumber. In NJ, a homeowner may work on their own single-family home but permits and inspections still apply; gas work is best left to licensed pros.

What temperature should it be set to?

Many manufacturers ship at about 120°F, a common balance between scald risk and comfort. Follow the manual and any building rules.

Sources & review

Last reviewed . General information, not legal or engineering advice. Rules change and individual buildings differ.

  1. NYC Dept. of Buildings, Plumbing Permits
  2. N.J.A.C. 13:32-1.4, Scope of practice

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