AquaMatic/AqMatic Valves, Controlers, Stagers and Ejectors


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Normally Open or Normally Closed?

To determining what type of AquaMatic valve you have, or need, one must figure out if they have a Normally Open or Normally Closed valve.  These are the base configuration of all AquaMatic valves. To understand what type of valve you need you must understand the operation of the valve.

AquaMatic valves are controlled by pressure.  The two main types of pressure that are used are line pressure and control pressure. Line pressure is the pressure that comes from the flow of air or liquids through the valve. Control pressure comes from a solenoid, float, manual pedal or a stager with a stager controller.

Normally Open Valves

With a Normally Open valve the pressure in the line of liquid or air flowing through it will keep the valve open unless control pressure closes it. To close the valve an equal or greater amount pressure than the flow must be entered into the control chamber above the diaphragm. This pushes the diaphragm down to close the valve. As the diaphragm chamber’s surface area is bigger than the flow inlet, an equal pressure will result in the valve closing.
Normally Open valves will usually have a pipe or tube going into the top of the valve for the control pressure to be applied.
The hole in the valve body below the diaphragm is usually used as an air vent and the shaft controlling the diaphragm closing is solid.

Normally Closed Valves


Normally Closed valves have a hollow shaft that allows the line pressure to flow into the diaphragm chamber. As the diaphragm chamber’s surface area is bigger than the flow inlet the diaphragm is forced down and closes the valve. This will keep the valve closed until enough pressure, added to the flow pressure, is entered below the diaphragm to force the valve open.

With the Normally Closed valve the hole on the top of the valve is usually capped or has a limit stop or position indicator and the pipe or tube with control pressure will enter the valve body under the diaphragm.



The most common way to tell if a valve is Normally Open or Normally Closed is to look for a plug at the top of the cap.

There are many types of AquaMatic valve and many configurations for each.  But after one has determined the valve type, determined material and use, and the size, the next step is to figure out this basic configuration.

Some application have “non-standard” implementation of the valves, but this is rare and with the above data one could get the right valve type most of the time.

AqMatic AquaMatic V42 Valves
AqMatic AquaMatic VAV Valves
AqMatic AquaMatic V46 Valves
AqMatic AquaMatic K52 Valves
AqMatic AquaMatic K55 Valves
AqMatic AquaMatic K53 Valves
AqMatic AquaMatic Stager Valves
AqMatic AquaMatic Stager Control Valves
AqMatic AquaMatic Ejectors Valves