Single Zone Pressure Drop on Hardie Controller System

One zone on a Hardie-controlled system has suddenly low pressure, but manual bleed operation yields full pressure. Other zones work normally.

Diagnosis

Manual bleed bypasses the solenoid—full pressure via bleed means supply pressure is good. The valve opens mechanically but not electrically.

Diaphragm failure. The diaphragm isn't lifting fully when solenoid activates, restricting flow. Common after 15+ years.

This is a $15-25 DIY fix versus $150+ service call. The diaphragm rubber degrades over time, developing tears or losing elasticity.

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