Three-way multiport ball valves can solve many application problems but only if you understand how they can be used to direct the system flow.

There are several options for both manual and actuated valves. Let's take a look at the manual valves first.

The illustration will help us to identify the valve ports and make talking about flow patterns easier.

The standard manual three-way valve is usually installed so that the bottom port "C" is the common port. Turning the handle 90 degrees diverts the flow to the right, port "A" or to the left, port "B", or turns the flow off.
 
 

Flow Schematics Top View Flow At NT Ball - Standard 0o Port A Port B 45o Port A Port B 90o Port A Port B Flow At  TW Ball 0o Port A Port B 45o Port A Port B 90o Port A Port B Flow At TP Ball 0o Port A Port B 90o Port A Port B

There's a couple of things to remember though. Let's say that the flow is now coming from the inlet port "C" and flowing out port "A". A quarter turn of the handle shuts the flow off, another quarter turn in the same directions diverts the flow to port "B". The flow can never go from "A" to "B" or from "B" to "A" without going through the off position. And with the standard ball the flow can never flow through all three ports at the same time.

An arrow on the top of the valve handle points to the port that the flow is going through or if the valve is in the off position, the valve handle is at right angles to the valve body.

OK, knowing that about the flow pattern can you come up with another way that the standard three-way valve can be installed that utilizes a different flow pattern? The standard three-way valve can be installed so that ports "A" and "B" are the inlets and port "C" is the outlet. This permits the valve to be used in mixing applications.

Say the flow is coming in from port "A" and going out port "C". A quarter turn of the handle turns the flow off, another quarter turn in the same direction takes the flow from port "B" and diverts it out port "C". In this case the arrow on the handle points to the valve inlet in operation, not the flow direction.

Suppose that the customer wants the flow to come from a single inlet, port "C" and flow out ports "A" and "B" at the same time? Or if he wants the two inlet ports "A" and "B" to flow out of "C" at the same time. What can he do?

The most common solution to the problem is to supply the valve with what's called a Tee Port Ball. This special ball opens all three ports at once, or closes them. The flow can never go through just two of the ports. The valve is either 
completely open or closed. With this configuration the arrow on the handle has no significance. When the valve is open the handle is parallel to the valve body and at right angles to it when it's closed, the same as a two way valve.

There's another, less expensive way to solve this piping system problem. In the last example with the Tee Port Ball what we did was to create an "automated" T Fitting! Another way around the problem is to use a regular T Fitting and install a on/off ball valve or other type valve on the "C" port of the Tee Fitting. Then opening or closing the valve diverts the flow in exactly the same way as the Three-way ball valve with a Tee Port Ball installed in it.

Actuated three-way valves work just like the manual ones with just a couple of exceptions. Standard actuated three-way valve do not have an off position. The flow is never shut off going from one port to the other. A special valve and electric actuator can be used if the application requires an off position. An actuated valve with a Type TW Ball is ordered along with an actuator with a 180 degree center off position option. This actuator/ball combination diverts the flow the same way as a manual three-way valve.

Electric and pneumatic actuators can also be sued with valves that have a T Port Ball. The flow operates just like a manual valve.