What a Tee Coupling Does
A tee coupling is a three-way brass fitting that splits a lubrication line at 90 degrees. One branch leaves the main run so a secondary point can be fed without breaking the line apart. The body is machined in C3771 brass, a designation chosen for machined fittings on grease and oil lines as used in centralized lubrication. Use it where a branch line must come off a main run and stay on the same supply. Where the branch needs to be added onto an existing line without cutting threads, the push-to-connect grease line fittings page covers those parts instead.
Declared Specifications
| Material | C3771 brass |
| Sizes | 1/8, 1/4, 3/8, 1/2 inch |
| Thread forms | NPT, BSPP or BSPT, selected when ordering |
| Configuration | Three-way, 90 degree branch |
| Service | Lubrication lines (grease and oil) |
| Pressure rating | Confirm when ordering; follows media and temperature |
Choosing the Thread Form
NPT and BSPT are both tapered, but they are not the same thread. The thread angle and the pitch differ, so the two forms engage part-way, jam, and do not seal at that point. Never interchange them. BSPP is parallel, not tapered, and seals on a gasket, an O-ring or a sealing shoulder, never on the thread itself. Before ordering, identify the mating hardware on both the run and the branch, because the tee has to match what it screws into at all three ports. State the size, the thread form and which port is the branch, written as run by run by branch. A bare fraction such as 1/4 inch does not say enough, since the same size can be had in several forms. Write it out in full on the order.
How It Is Used in Lubrication Lines
The common job is a branch take-off from a main supply line to a secondary lubrication point. A second use is a gauge take-off, where the branch feeds an indicator rather than a delivery point. A third is dividing one supply into two runs where a single line would run too long to serve both ends well. On a branch that must not backfeed into the main run, pair the tee with an in-line check valve so flow is held in one direction. Coarse upstream protection, to keep hard particles out of the tee and the points beyond it, is covered on the Y-type strainer page.
Installation
Identify the thread form at each port before applying thread sealant, because sealant will not correct a form mismatch. Apply thread sealant in the direction of the thread, working it into the valleys rather than across the crests. Hand-start every joint and turn it several threads by hand to confirm the forms match before any wrench is used. Tighten by feel. A joint that stops early is a form mismatch, not a tight fit, and forcing it damages both threads. Bring the line up gradually and check for weeping at all three joints. If weeping appears, stop, break the joint and inspect the threads before retrying. Note that pressure, temperature and torque values are not declared for this part, so confirm against your media and temperature when ordering. For a quotation, use the contact for a quote page.
What Is Supplied
One tee coupling. Confirm the size, the thread form and whether an equal or a reducing tee is required when ordering. Gaskets or O-rings for BSPP ports are confirm-when-ordering items, since the sealing method depends on the mating shoulder and the media. No other parts are included in the supply.
Frequently Asked Questions
Which thread forms are available?
NPT, BSPP or BSPT, chosen when ordering. State the form for all three ports.
Can NPT and BSPT be mixed?
No. The angle and pitch differ, so they jam part-engaged and do not seal.
How does BSPP seal?
On a parallel thread, sealing happens at a gasket, O-ring or sealing shoulder, not the thread.
What sizes are listed?
1/8, 1/4, 3/8 and 1/2 inch. Confirm the three port sizes when ordering.
What is the material?
C3771 brass, machined for lubrication line service.
What is the pressure rating?
Confirm against your media and temperature when ordering. It is not separately declared.
Are all three ports the same size?
Equal and reducing versions are both possible. Confirm the three ports when ordering.
Can it carry grease and oil lines?
It is declared for lubrication lines, grease and oil as used in centralized systems.
How do I stop leaks?
Use the correct thread form and the right seal method. Check for weeping after pressurizing.
How do I get specifications and a quotation?
IsoHiTech Lubrication Systems, founded in 2023, engineering since 2006, builds and supports every unit. Email inquiry@isohitech.com for specifications and a quotation.
For a quotation, use the contact for a quote page.
