Tank Mixing Eductor Purchasing Guide

Tank mixing eductors are used to keep the contents of a tank mixed. They're typically connected to a recirculating pump and submersed in the contents of the tank. BEX eductors use a unique venturi design which enables smaller pumps to circulate large volumes of tank solution. The eductor will circulate 4 to 5 gallons of solution for each gallon pumped, resulting in quick, efficient mixing.

Some common uses for tank mixing eductors include:

  • Mixing chemicals
  • Suspending solids
  • Adjusting PH levels
  • Sweeping Debris or Sludge toward a Filter Intake.
  • Heating the contents of a tank by injecting steam

This page is designed to help our customers determine the best way to set up eductors for any application. This includes deciding the type of eductor, how many to use, appropriate layout/orientation, pipe size and pump size. For basic troubleshooting, please see our troubleshooting guide.

For further assistance, please contact the BEX customer support team, and we will be happy to help you directly.

Download PDF Eductor Catalog

BEX Eductor Advantage

Eductors are an ideal solution for tank mixing applications. Unlike mechanical agitators or compressed gas, they do not rely on costly mechanical parts, which are difficult to repair. Unlike compressed gas injection, tank mixing eductors will not alter the chemistry of the tank contents.

The main problem with using a mechanical agitator is that they require multiple propellers, a shaft, and motor assemblies to be positioned in the tank. These assemblies take up a lot of space inside the tank, and in many cases, they can restrict or further complicate how a work piece can be positioned or moved inside the tank, especially when being lowered or raised. The mechanical components in an agitator system are also costly to repair, require frequent maintenance, and take a long time to install and replace.

Another common method of mixing the contents of a tank is to use compressed gas. Using compressed gas in a tank can drastically change the chemistry of the tank.The bubbles produced by compressed gas injection can entrain vapours from the tank liquid. When these bubbles break the surface they produce a mist of process liquid which can migrate from the tank, creating a mess around the outside of the tank. Depending on the process this mist can be harmful to people and corrosive to other equipment in the facility.

None of these problems are present in an eductor system. It is far easier to remove an eductor that requires repair or replacement than any other tank mixing system. Due to the relatively small size of eductors, they are easy to aim at trouble spots, and can be effective in a wide variety of tank mixing layouts. There are no moving parts in an eductor system, with the exception of the pump, which is located outside of the process tank. Most importantly, BEX eductors are manufactured in-house and incorporate a unique venturi design which increases the mixing and agitation in the tank. This means that the time required to achieve an acceptable mix is greatly reduced, which improves the efficiency of any coating, plating, or cleaning applications.

Obtaining Optimal Eductor Performance

The unique venturi design of a BEX eductor enables smaller pumps to circulate larger volumes of tank solution. One eductor will circulate 4 to 5 gallons of solution for each gallon pumped with solutions that maintain a similar viscosity to water.

Those unfamiliar with how eductor systems work should be aware of the following:

  • There are four main components to an eductor system. The tank, eductor(s), piping and pump.
  • Agitator mixing systems are not be used in conjunction with an eductor because an eductor requires a minimum liquid velocity at the orifice of the nozzle section in order to work properly.
  • If the pump is undersized, it won't be able to push enough liquid through the eductors to maintain that minimum velocity.
  • If the piping is undersized, there will be too much resistance to flow in the system and the minimum required velocity won’t be achieved.
  • If the piping has too many bends, it can create turbulence in the piping, which means that the resistance to flow is increased and the agitation/mixing obtained from the eductor will be reduced.
  • If the tank is too large for the specified eductor/pump system, the operator won't achieve the required mixing in the tank, resulting in poor performance.

Eductor Orientations

Determining the best eductor orientation depends on the application. Each application has its own set of determinants for size, quantity and placement.


  • Cylindrical Tanks
  • Spherical Tanks
  • Elongated Tanks
  • Rectangular and Square Tanks
  • Stratified Layers Tanks

Directional Sweeping

  • Electrocoat Tanks

Tank Agitation

  • Parts Cleaning Tank
  • Rack Plating Tank

Keeping Solids in Suspension

Determining the Pipe/Pump Size

In order for an eductor system to work properly, it is vital that the necessary pump and piping be considered. Variables such as the power of the pump, the sizing and number of bends in the pipe, the size of the tank, the density of the liquid, and the distance between the eductor and the surface of the liquid, will all play a factor in how effective an eductor system is at reaching the desired rate of circulation in the tank. To help determine the required flowrate and pressure for what you want to accomplish, whether it be mixing, sweeping or agitation, one must work backwards from the eductor and determine the required pressure output of the pump.

Refer to the diagram and equation below, and contact us for any additional assistance.

Common Tank Styles

Storage Tanks

Lubricant manufacturers use large tanks to store their lubricants. Over time the components that make up that lubricant will tend to separate out. Mixing is required to maintain a homogenous mix in the tank.

Blend Tanks

Lubricants, perfumes and other products are a mix of various components. To blend these components they are often combined in a large tank and require mixing.

Chemical Reactor Vessels

Industrial chemical reactions often take place in a reactor vessel (PH control). The reaction rate depends on the contact area between the components. Mixing is used to increase the contact area and reduce the reaction time.


Applications such as fish ponds and some waste water processes require air to be mixed in with the water. Eductors can be used either through direct injection of compressed air or through entrainment of atmospheric air.

Steam Sparging – Explained

A steam sparger is any device used to inject steam into a tank liquid for the purpose of heating the tank liquid. Eductors make very effective steam spargers.

When steam is used to heat a tank liquid, there is the risk of damaging the tank due to cavitation of the steam bubbles. Cavitation occurs when a steam bubble implodes. When steam is injected into a relatively cold liquid some steam bubbles cool down until they reach the temperature where water vapor liquefies. When the vapor in a bubble liquefies the volume occupied by the bubble decreases by a ratio of close to 1:1000.

Cavitation can occur very quickly, and it can erode or create a hole/pit in the tank. Liquid rushes in to fill the hole. This creates a shock wave of moving liquid very similar to the shock wave created by an explosion. Shock waves from multiple implosions are sometimes strong enough to damage a tank or its foundation.

The solution to cavitation is to break the steam up into very small bubbles to minimize the shock wave from each implosion. A BEX eductor works well as a steam sparger because of the mixing action of our diffuser. Steam is injected into the eductor and the nozzle section forms it into a high velocity jet. This jet entrains tank liquid in the normal way and the tank liquid and steam jet are mixed in the diffuser in the normal way. The mixing is so thorough that the steam bubbles in the eductor discharge are very small. As such the shock waves created when they implode aren’t strong enough to do any damage.

In order for an eductor to be effective as a steam sparger, there must be enough steam pressure supplied to the eductor to create a high velocity steam jet out of the nozzle.

Steam Sparging – Selecting the Right Eductor

Calculate the required steam flow rate from the following equation:

Knowing the steam flow rate and the steam pressure available at the sparger, choose the sparger(s) from the table below. Using several small spargers may be advisable to using one large sparger.

To help eliminate steam hammer, ensure that the absolute pressure at the eductor entrance (P1) is at least twice the absolute pressure inside the tank at eductor depth (P2).