Bull Hose Configurations - Ground Joint Couplings & Hose Layouts

A ground joint female hose coupling set includes  hose   stem, female NPT spud, and hammer swivel .  The seal on the nose of the spud creates a tight seal when the hammer swivel pulls it against the hose stem.

A ground joint female hose coupling set includes hose stem, female NPT spud, and hammer swivel. The seal on the nose of the spud creates a tight seal when the hammer swivel pulls it against the hose stem.


There are a few different possibilities in how to lay out a bull hose configuration. Most pump hose or water hose assemblies are configured with male and female ends. So when we ask a client how they want their bull air hose assembled a common reply is "with male and female ends".  But when multiple lengths of large bore, heavy, bull air hoses are connected in line, using female ends and double spuds can be of benefit. Here we review the types of couplings in the ground joint product line , optimal configurations, and how not to end up with a costly box of extra spud adapters.


Lets start with Bull Air Hose. (or Steel Braid Air Hose). A Bull Hose is essentially a large bore (1.5 to 4 inch) wire or heavy fabric reinforced supply hose that connects the air compressor to the downstream compressed air system and air tools. When running multiple air tools from a single compressor, the bull hose typically connects to a manifold or receiver tank, where smaller (1/2 to 1 inch) lines are run to each tool. (Each branch line should have its own safety check valve and whip check restraints.) Even though we are focusing on Bull air hose, this blog can also be used for steam hose configurations. Just ensure that ALL components, hose, and clamps are appropriately rated for steam service.

As the bull hose is large bore and typically wire reinforced, it can get rather heavy - a 3 inch X 50 foot hose assembly is roughly 200 lbs. Once several lengths of these heavy hoses are rolled out, having to reconfigure because the couplings do not match up is quite an effort. How do you avoid having two male ends that do not mate rather than a male and a female? Is it possible to have all hoses in your fleet interchangeable and all ends matching? Configuring all hose with female ground joint swivels and then using double spuds and threaded spud adapters can make for quick setup and decreased frustration.

Before we go any further, what about 4-lug Chicago couplings? Doesn't that solve these issues and make installation easier? Well yes but mostly no. They are only available up to 2 inch diameter, leaving 3 and 4 inch with no similar option. They are only rated to 150 PSI, where these hoses are often rated to 600 PSI or more. An assembly is only as strong as its weakest component. Finally, getting even a 1/4 turn out of a big heavy air hose can be quite a chore when multiple hoses are being laid out in a long hose run. For these reasons we recommend the ground joint coupling system which we will focus on from here:

The ground joint female hose coupling has its own coarse thread type that does not interchange with NPT parts. This is integral to the design of the coupling set because it allows the wing nut to be quickly hammered open and closed without thread damage, but is also a nuisance in configuring piping, hose and components.

An NPT Spud is an adapter that converts the ground joint thread back to male or female NPT (see photo above, center component). A Double Spud has the wing nut male thread on both sides (see below/ right).  You can differentiate between the double spud and male NPT spud by checking for a black ground joint seal on the nose of the ground joint thread. A double spud would have this seal on both ends.

The Double spud is the key to the female X female ground joint hose coupling layout. Thread into one hose, then hammer-swivel the female wing nut from the next hose until tight. Continue assembling until the entire daisy-chain of bull hoses are connected.

At the end of the series of connected bull hose assemblies (and at the start), a male or female NPT spud adapter is needed to join the hose to standard NPT pipe fittings, valves, and other piping.

The female ground joint set (shown above) typically includes a female NPT spud. In a male X female hose configuration, the female spud would be removed from the female coupling set and installed on the male NPT of the connecting hose, converting its thread. (A male wing nut thread hose stem is available, but costly, and difficult to adapt from if a configuration needs to be altered). 

The extra female spud can be used to thread to the air source or manifold. However, each hose assembly in a chain of the female X female plus double spud configuration does not require this adapter. If included with each female, you would have far too many for this configuration. Instead of collecting these parts (and paying extra for them), request that the ground joint coupling on all hose assemblies have the female spud omitted, and use that cost savings to help pay for the expense of the double spuds!

And that is, in our opinion, the optimal configuration for a long run of interconnected bull hose assemblies.


Install an appropriately rated hose safety cable at each hose connection and from the equipment to the hose line

We can supply a complete 7 gallon ASME air receiver tank with (1) 2 inch ground joint female inlet and (7) 2-lug Chicago valved outlets meeting OSHA 1910.169 and 1926.306 complete with pneumatic safety check valves, pressure gauge, and safety pop-off valve. Inquire for standard and custom designed options.