Paloma Legacy Tankless Water Heaters

Paloma Legacy tankless water heater

The Paloma Legacy series is a group of tankless water heaters that have a very simple design and are used for indoor and whole-house water heating.

Legacy models are wall-mounted gas appliances that are produced in three sizes/models: Paloma PH6, PH12, and PH24.

The smallest PH6 units are perfect for hot water heating applications in cottages, cabins, and small offices. The PH12 model is recommended for the average home size and PH24 for the large residential homes, even commercial use.

All Legacy models are different (or less sophisticated) from previously reviewed Digital 5.3, 6.6, 7.4, and 9.5 tankless models when the design, venting installation options, available features, and parts are taken into account.

Paloma Legacy water heaters use a galvanized atmospheric B-type vent, with 4", 5", and 7" diameter. This is a cheaper solution than the direct vent systems and their stainless steel vents. The venting system will involve a long vertical vent run.

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Features and benefits

Legacy models are ideal for homes where the water pressure is low, usually under 40 psi, and if the electric power is a problem or unavailable.

Also, in order to start heating, the minimum water flow has to be reached, which is 0.6 gallons per minute for PH6, 0.48 GPM for PH12M and 0.52 GPM for PH24M models; while the minimum incoming pressures are 2.1 psi for PH12, 2.4 psi for PH24M and 4.3 psi for PH6.

The largest Paloma Legacy model is PH24M, and it provides a maximum water flow of 6.5 gallons per minute, or up to 264 gallons per hour (with 64 F rise). This is assumed for southern, warmer areas (Sunbelt), where the incoming cold water temperature is 60 F; while in northern and colder regions, where incoming water is 40 F, the water flow is around 4.4 gallons per minute.

Thanks to the modulating gas valve, Paloma PH24M tankless water heaters can provide between 37,000 and max of 178,500 BTU/hr gas input. The PH12M unit works with the gas input range between 30,000 and 89,300 BTU/hr, while the PH6 model has a constant gas input of 43,800 BTU/hr.

This is done by using mechanical modulation to keep the temperature consistent when changing the faucet's flow.

The PH6 model doesn't use modulation to adjust the power when the water flow changes; it remains constant. Since the gas burner has only one stage, the temperature is adjustable by the volume of water flow that passes through the heater.

Hot water temperature is controlled manually, on the unit, by using the temperature adjusting spindle. The temperature is controlled with this warm/hot knob so that you can set the temperature between 60 and 100 F above incoming cold water. The bath controller and the Main controller are not available for Legacy Paloma tankless water heaters.

Paloma Legacy models use a standing pilot light and built-in piezo igniter to light the pilot flame and the main burner. Within this assembly is a thermocouple, a safety element that informs the magnetic safety gas valve to stop the gas delivery when the pilot light is extinguished.

Legacy water heaters are energy-efficient units with 80% thermal efficiency, but they are not Energy Star qualified, even with such a simplified technology and pilot flame.


Safety features that these heaters are using to protect the system are:

  • Overheat limiting device installed on the heat exchanger
  • The temperature limiting device automatically shuts off the gas to the main burner and the pilot light when the temperature exceeds 194 F
  • Thermocouple
  • Magnetic safety valve

You can buy Paloma Legacy tankless water heaters from $550 to $1400 for the largest PH24M model. Paloma provides a 5-year limited warranty on the heat exchanger and 3 years on other parts.

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