This can only be done when the outlet temperature of the tank preceding the valve
is hotter than the valve setting.
Check expansion tanks with diaphragms in closed loops by very briefly depressing
the schrader valve stem. (Figure 6-6) If any fluid comes out, the diaphragm is
leaking and the tank must be replaced.
Schrader Valve on a
Repeated testing of diaphragm-type expansion tanks as described
above will eventually release enough air to interfere with proper
operation. Whenever the fluid is removed from the loop, the air
pressure of the tank should be measured and necessary air pumped
6.1 MAINTENANCE PROCEDURES