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Autofill probe
A stainless probe inside the steam boiler that detects the water level by electrical conductivity, telling the autofill solenoid when to refill.
Category: Water System
An electrical sensor that detects the water level inside a steam boiler. When the water drops below a set level, the autofill circuit triggers the pump to refill the boiler from the supply line or tank.
Why it matters — Autofill keeps the steam boiler at the right level without manual intervention. Without it, the boiler eventually runs low, the heating element starts running dry, and the element can burn out.
Good to know
- Scale buildup on the probe is the most common failure mode. The probe relies on water conductivity; scale insulates it.
- Probes can usually be unscrewed, soaked in descaling solution, and reinstalled. Replacement is inexpensive if cleaning doesn't work.