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How to Test a Zone Valve


A Couple of Simple Methods for Testing a Zone Valve


By Mark J. Donovan




Question: One of the zones on my hot water heating system is not working properly. How do I test a zone valve to see if it is working?

Answer: Hydronic zone valves are used in hot water heating systems. Zone valves work in conjunction with the thermostat, a transformer, a circulator pump and the boiler. When the thermostat is turned up higher than the temperature in the room, the zone valve normally turns ON and hot water is circulated through the heating elements in that heating zone.


To test a zone valve, first turn up the thermostat to its maximum level and feel and hear for hot water circulating around the heating elements. If you do not feel or hear any hot water circulating around the heating zone, pull down on the lever on the zone valve to force the valve open. If the lever goes down easy, without any resistance, chances are the problem is not with the zone valve.  If the lever is difficult to pull down then the zone valve is likely a problem.


With the zone valve lever in the down position, and little resistance was felt when pulling down on it, hot water should begin to circulate around the heating elements associated with the particular zone. If hot water does not begin to circulate through the heating elements then chances are there is a problem with the zone valve, circulator pump or boiler.

If there is one common circulator pump driving all of the heating zones, and the other zones are working properly then you can rule out the circulator pump and boiler as a problem.

If you have a multimeter handy you can also test a zone valve to see if it is being properly powered by the transformer that supplies a 24V voltage to it. Set the multimeter to read DC voltage up to 50 volts.

Then measure the voltage across the wires coming from the transformer that connect to the zone valve. If you do not measure a 24V voltage then chances are the transformer is bad. If you do measure a 24V voltage and there is a common circulator pump feeding all the zones, and all the other zones are working then chances are the thermostat or zone valve is the problem.

If after evaluating the hot water heating system and testing the zone valve you determine that there is indeed a problem with the zone valve, call a plumber.

Hydronic zone valve in a hot water heating system.

Photo by Mark Donovan

Do not attempt to remove the zone valve head yourself. Removing a zone valve head while still powered by the transformer or while it is still hot could lead to electrocution, scalding and other injuries.

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- How to Test a Zone Valve -

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