Modulating or float valves are used in surge tanks or vacuum D.E. filter tanks when the top of the tank is at an elevation above the maximum pool water level. In this type system, the water level in the surge/filter tank will rise to the same level as the pool water level when the system is shut down.

How does a modulating float valve work?

The valve closes drip-tight at the maximum level and modulates to maintain the tank level. The float pilot is remotely installed at the high level in the reservoir tank. Movement of the main stem alters the size of the closing restriction, interrupting the tendency of the valve to hunt.

What is a modulating valve?

A modulating control valve is an automated valve that is used to control the amount of flow in a system or process. They go beyond simple shutoff or isolation (on/off) and actually allow precise control of the flow rate.

The float valve is a simple mechanical liquid level controller. A float detects changes of elevation in the liquid free surface and opens or closes a valve accordingly. Large numbers of small float valves are used in domestic water systems.