An altitude gauge is required on a hot water supply boiler at altitudes over how many feet?

The correct threshold for requiring an altitude gauge on a hot water supply boiler is set at 20 feet. This requirement is tied to safety and operational standards that aim to ensure that water boilers function properly at different elevations.

When installed in areas above this altitude, pressure and boiling point of water can change, impacting the boiler's performance and safety. An altitude gauge helps monitor these variations, allowing for proper adjustments and ensuring the system operates within safe parameters.

In jurisdictions like Massachusetts, adhering to these regulations is crucial for maintaining the integrity and safety of the boiler systems, making it essential that personnel are aware of the requirement at the 20-foot mark. The specific value indicates a critical point at which the dynamics of pressure significantly differ from those at sea level, prompting the need for monitoring to safeguard both equipment and personnel.