Balboa Caldera/Watkins 4kW 240V Low Flow Trombone Heater, C3473-1

The Balboa C3473-1 is a 4kW, 240V trombone style replacement heater for Caldera and Watkins spas. It is the low flow version, built for tubs whose circulation runs slower than a standard system.

Why low flow matters

A spa heater needs water moving past the element to shed heat safely. When circulation drops, an ordinary heater either trips its hi-limit or heats unevenly. The trombone body on this heater is shaped to keep heat transfer steady at reduced flow, which is why it suits models such as the Caldera Utopia and Paradise Series.

Safety and fitting

The flow switch and the hi-limit sensor are both part of the assembly, so the heater only energizes when conditions are right. Plumbing is through 3/4 inch hose barbs, and the 40 inch pigtail cord gives enough length to reach the control pack without splicing.

The same heater is cataloged elsewhere as 26-3473-1-5T-K by HydroQuip, 74912 by Watkins and SEH-4300-NHW by Laing. If your old unit carries one of those numbers, this is the replacement.