What is a Liquid Level Control System?

Many industries use various equipment to maintain fluids, or even fluid-like substances, at a certain level. A liquid level control system utilizes various floats, probes, and other simple or complex technologies to moderate fluid levels. Some of these systems, processes, and implements can also be used with dry powders, chemicals, or any material that flows. Though some of these systems are versatile and have multiple applications, it’s important to understand the purpose for which it is used to ascertain the best type and method for liquid level control for a specific application.

Keeping It Level: Liquid Control Systems & How They Work

The purpose of these systems is relatively simple: to maintain containers holding liquids or liquid-like substances at a specific level. Liquid control systems use probes to help detect fluid levels in tanks, vats or other containers, filling them when levels are too low or releasing fluid when levels become too high. These systems normally also utilize electrical devices to control the level of liquid, though this can also be done by mechanical means with floats.

What Makes a Liquid Level Control System?

To maintain fluid level, liquid control systems consist of specific implements.

The main components of these control systems consist of:

  • Controller that maintains liquid levels by stopping or starting pumps based on data received from the measuring devices.
  • Dump valve that releases fluid from the tank once it reaches a certain level.
  • Fluid tank for storing liquids.
  • Measuring devices, such as stainless steel floats, physically or electronically sense liquid levels within the tank.
  • Pump that feeds into the tank, which the controller regulates.

The controller monitors fluids in liquid control systems to ensure they’re maintained at a set level within the fluid tank. Most types of processing equipment utilize these controllers, which work in conjunction with measuring devices within the tanks. Used in various applications, these devices control the movement of liquids into and out of the storage tank.

How Liquid Control Systems Work

Using a float to measure the fluid level, liquid control systems send signals either electrically or pneumatically to the controller when the fluid level goes under or over a certain point. This causes an automated control valve – also called a dump valve – to open when the level of liquid reaches the high set point, thus releasing fluid from the tank. When liquid levels reach the low point, the measuring devices within the tank send a signal for the pump to fill it up.

Benefits of liquid control systems include: 

  • Allows operators to replicate liquid levels based on past levels.
  • Automatically compensates for changes in pressure settings to provide a more stable and controlled flow rate.
  • Enables manufacturers to increase the volume of liquids processed in industrial settings.
  • Increases automation, thus decreasing labor costs.
  • Moderates and precisely controls flow rates of liquids to minimize the impact on flow valve outlets or inlets due to pressure.
  • Permits faster throughputs of liquids and liquid-like materials.
  • Provides accurate measurement of fluid levels.
  • Reduces waste by more consistently dispensing fluid.

To choose the best liquid level control system and implement it for the application, it’s best to ask for expert advice.

Maintaining Fluid Level: Liquid Control System Types & Applications

These systems use three main methods for controlling and maintaining fluid levels at certain points. These offer adjustable, non-adjustable, or modulating levels of control. The adjustable and non-adjustable methods involve turning the flow on or off, whereas the modulating method enables operators to increase or decrease flow rates. Additionally, the two systems that utilize on/off controls use floats to measure fluid level or probes that measure conductivity. Those that utilize a float rely either on the movement of the control valve directly or electrical switches triggered by the float’s movement upon the liquid’s surface.

Used for controlling fluid levels, liquid control systems generally are of the following types: 

  • Differential pressure: Measures pressure differentials between atmospheric, dynamic and hydrostatic pressures, capable of measuring incremental changes in pressure as it relates to the output signal range.
  • Float operated: As a float rises or falls with the level of liquid, these systems cause switches to adjust when levels reach certain points.
  • Hydrostatic: Measures pressure differential between outside atmospheric pressure and hydrostatic pressure of the liquid at its high point above the sensor, using a pressure transmitter.
  • Magnetic: Utilizes a float or cone that rises or falls, along with a stainless steel probe that’s held in the fluid being measured; this float then interacts magnetically with switches outside the tank to send data to the controller.
  • Microwave radar: Uses a high-frequency pulse of electromagnetic energy from a transducer, then bases measurement of fluid levels on the time it takes to rebound to the sensor.
  • Solid probe: Measures conductivity or electrical capacity to adjust fluid levels.
  • Steel rope capacitance: Uses flexible steel rope suspended within a liquid that measures the change in an electrical capacity as fluid levels change.
  • Torsion: Features a moving float spindle that changes in relation to the float’s twisting action, which is measured by a specialized transducer.
  • Ultrasonic: Similar to the microwave radar type, it senses a high-frequency acoustic pulse directed from a transducer, measuring levels of liquid based on the time it takes for this pulse to rebound back to the sensor.

These liquid level controllers are used with a wide array of processing equipment, including well testing systems, separators, reboilers, heater treaters, free water knockouts, contact towers, compressor scrubbers, and coalescing filters. Applications also include a variety of other household and commercial applications, such as boilers, water heaters, pasta cookers, thermalizes, and steam tables. Additionally, chemical processing, water treatment, sewage, food processing, transportation, and other industries utilize control systems for tracking liquid levels in tanks and other types of containers.

Chemical Processing & Storage

In the chemical processing sector, along with other industries that store and utilize chemicals, control devices like float balls are integral for maintaining fluid levels. Liquid control systems are safety systems in facilities that store chemicals while also moderating chemical fluids’ viscosities and compositions. When maintaining fluid levels, liquid control systems often need to deal with chemicals that are mixed, heated or cooled, which alters their properties.

Liquid control systems, along with measuring implements like floats, need to withstand harsh conditions that may include extremes in temperature and corrosive chemicals. These systems play an important role in chemical processing and storage applications. They’re used for mixing chemicals, monitoring inventory in tanks, and other aspects of the chemical industry. In such settings, using stainless steel float balls helps mitigate the corrosive properties of certain chemicals.

Water Treatment

Controlling liquid levels in wastewater treatment plants requires particular precision. A key piece of equipment for filtering, heating, cooling and treating wastewater involves a vertical fluid switch, which consists of a float and rod. Water treatment also involves an array of aerobic digesters, chemical tanks, process basins, sludge tanks, and other containers, where these controllers prevent overflows as well as protect pumps from cavitation that could cause them to fail.

Sewer Systems & Sump Pumps

Residential sewer systems and sump pumps must also maintain a certain water level. Liquid control systems designed for this application utilize float balls, float valves, and other pieces of equipment for septic systems and wet wells, helping to prevent overflows. To prevent property damage from groundwater flooding in basements or other areas with unwanted water, sump pumps also utilize these liquid control systems to eliminate excess water.

Food Processing

Liquid and liquid-like ingredients used in the food processing industry are stored in large tanks that require management of their fluid level. Liquid control systems often utilize float balls to indicate how full these vats are. While used for edible foods and potable beverages, these fluids often are alkaline or acidic and corrosive, which is why food processors typically utilize stainless steel for their measuring floats. Stainless steel protects equipment from products containing concentrated citrus, dairy, vinegar, or other ingredients.

High pressure is also a factor in food processing, as pressure changes occur when products are heated, mixed, or concentrated. As temperatures change, this can create pressurized steam, which can cause explosions. This is another reason why float balls for food processing plants are usually made from stainless steel, as it better withstands high pressures.


Tanker trucks that transport liquids like chemicals, sewage, and water also need some way to control fluid levels. Liquid control systems act once a tank’s reached its limit, shutting off the suction line that pneumatically fills the tanks. Using a float ball to prevent over-filling a truck’s tank, once this float reaches the top, it triggers a switch that prevents the vacuum hose from taking in more fluid. These float balls also need to be robust enough to withstand collisions against the side of the tank and movement of potentially corrosive liquids within it, along with temperature changes.

Liquid Level Control Systems from Arthur Harris

As a leading manufacturer of stainless steel float balls, Arthur Harris & Company has significant knowledge about applications that require our customers to maintain specific fluid levels. Liquid control systems are well within our capabilities, for which we make floats with various connections, gauges, metals, shapes, and sizes, along with other implements for controlling liquified materials. We also make many of these to our customers’ specifications.

For liquid control systems and other related uses, our products include: 

  • Round float balls made from stainless steel work well in pressurized, high-temperature environments to measure water or corrosive fluids.
  • Floats utilizing a thru-tube, also known as a guide tube, allow the float to slide up and down along the tube with the liquid, which often utilizes a ring magnet within the float to signal when a tank is full or needs filling.
  • Hemispheres and shells can be assembled into stainless steel floats and are available in various gauges.
  • Float valves mechanically control liquid levels within tanks, detecting changes in fluid elevation to open or close the valve accordingly.
  • Oblong floats are used similarly to round floats, are available in multiple sizes with a range of options, and are often used for applications where space is limited.

Contact Arthur Harris to learn more about how we can help with your application to regulate fluid levels with our liquid level control system implements.