Which Size Inlet & Threads for Your Sprinkler Heads?

When placing your order for complete sprinklers, case assemblies or just cases from SportsTurf Irrigation, you will be asked two key questions: “What size inlet?” and “Do you need ACME or NPT threads?”

This information is essential for installation of a head in the field.

Sizing:

Cases come in 1″, 1 1/4″ and 1 1/2″ inlets for Rain Bird® and 1″ and 1 1/2″ for Toro®.

To measure your sprinkler head, measure across the bottom opening of the case, where it would thread on to the swing joint.

Threads:

NPT threads seal against each other to prevent leakage and ensure secure connections, while an ACME thread contains an O-ring to create a better seal.

So, how do you decide which you need?  What’s most common?

As a general rule, most of Rain Bird cases are ACME threaded while the majority of Toro cases are NPT threaded.  However, it’s the swing joint fitting in the ground that determines which type of threads are needed for your case. (Note: You can use a pipe fitting to adjust from ACME to NPT or vice versa if you prefer.)

Most Toro customers tend to order NPT cases for their Toro sprinklers as ACME threads for Toro cases are less common.

Although Rain Bird no longer offers NPT threaded cases, many of our customers still have the older heads. Fortunately, SportsTurf Irrigation has a solid supply of NPT threaded Rain Bird cases, case assemblies and complete heads, as well as ACME options.

How Can You Identify? 

If you look inside the bottom of your case, is it threaded only about a third of the first circular section? If so, that’s an ACME case.

An example of a case with ACME threads.

If the threads continue down throughout the first circular section, those are NPT threads.

An example of a case with NPT threads.