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Water Heater 101



Recently Rheem published a post with a guide for hot water tank plumbing terminology we thought you might find interesting! Reviewing the different water heater components can help you understand how a water heater works.


Anode rod – The sacrificial metal rod (usually magnesium or aluminum) in the water heater that attracts corrosive material like minerals and sediment and protects the inside of the tank. Have a plumber inspect your anode rod every year to extend your water heater’s life.

Flushing – A routine maintenance that involves turning off your water heater and flushing out sediment buildup.

Gasket – A closed, sealed refrigeration system that makes heating water extremely efficient. If worn or broken, water will leak from the gasket.

Heating element – The device that heats water in electric water heaters.

Heat exchanger – A device that transfers heat from the burner to water. It’s the main component in tankless gas water heaters, which heats the water on demand.

Mixing valve – A mechanical or electrical device that mixes cold and hot water to deliver tempered water. A mixing valve placed on the outlet water connection ensures water leaving the tank is a safe set temperature even if the water in the tank is super-heated above 120°F.

Combustion chamber – The part of the gas water heater where air and fuel are mixed to create combustion. Gas water heaters manufactured after 2003 have sealed combustion chambers where the gas pilot is lit using an ignitor mechanism.

Pilot assembly – Consists of a pilot, ignitor and thermocouple that connects the burner and the gas valve. Pilot is a small flame that ignites fuel from the open gas valve traveling to the burner.

Thermocouple – A sensor used to detect the presence of a pilot flame. It’s a crucial safety device that prevents the release of flammable gas if the pilot light is out. This is the part usually replaced, not the burner.

Rating plate – A label on the water heater that lists information about the unit: model number, serial number, manufacturer, warranty length, when it was manufactured and other essential information. Locate it on the water heater so that you’re prepared to take a picture or provide information for your plumber.

Shut-off valve – An accessory part of the water heater that helps protect your home from water damage. When liquid is detected by the leak sensor rope, the valve shuts off the inlet water supply to the water heater limiting leaks.

T&P (temperature & pressure relief) valve – A safety feature designed to protect water heaters from overheating and over-pressurization. If the tank pressure or temperature exceeds normal limits, the valve opens releasing water through a pipe preventing tank unsafe conditions.

Thermostat – A mechanical switch on non-smart water heaters that turns the heating element or burner on or off. The switch opens turning the elements or burner off when water reaches desired temp and closes when the water temperature cools. There can be two thermostats: an upper and lower thermostat, each sensing the water temperature at the top and bottom of the tank.

Thermistor – A resistor on smart water heaters assists the control board in regulating the water temperature. It produces electrical resistance (measured in ohms) based on air or water temperature. The control board reads the ohms and determines water heater response.


Here at Service First Tradeworks Ltd. we specialize in installing gas and electric hot water tanks as well as on demand tankless water heaters. For all your plumbing, heating, and cooling needs give us a call at (250) 804-4868 or (250) 675-3668.

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