The MECH grooved mechanical tee (grvd), model 3G, in ductile iron, sizes 2″ × 1-1/4″ – 10″ × 4″ (DN50×32 – DN250×100), working pressure up to 400 PSI depending on size, UL / FM / VdS / LPCB approved depending on size. This guide explains what it does and how it works, compares it with related models, and covers technical data, the critical point in selection and installation, and common mistakes. For more, read the technical library guide.
At a glance
- A mechanical tee takes a branch off an existing pipe without cutting or welding: the pipe is drilled to a set diameter, then a two-piece housing is clamped around it with a gasket sealing round the hole, giving a grooved or threaded outlet.
- Sizes 2″ × 1-1/4″ – 10″ × 4″ (DN50×32 – DN250×100) — working pressure up to 400 PSI depending on size.
- Approvals: UL / FM / VdS / LPCB (vary by size).
- Material Ductile iron ASTM A536 Gr. 65-45-12, gasket Grade “E” EPDM (fire sprinkler).
- Designed to ASTM F1548, AWWA C606, ISO 6182-12.
What is a mechanical tee and how does it work?
A mechanical tee takes a branch off an existing pipe without cutting or welding: the pipe is drilled to a set diameter, then a two-piece housing is clamped around it with a gasket sealing round the hole, giving a grooved or threaded outlet. A mechanical cross gives two opposite outlets.
It is a quick way to add sprinkler, drain and gauge branches, and to modify existing networks.
Models in the same family
| Model | Item | Sizes | Max pressure | Approvals |
|---|---|---|---|---|
| 4J | MECH GROOVED MECH CROSS (THD) | 2″ × 1″ – 10″ × 4″ | 300 PSI | UL / FM |
| 4G | MECH GROOVED MECH CROSS (GRVD) | 2″ × 1-1/4″ – 10″ × 4″ | 300 PSI | UL / FM |
| 3L | MECH MECHANICAL TEE U-BOLT | 1-1/4″ × 1/2″ – 6″ × 1-1/2″ | 300 PSI | UL / FM / VdS |
| 3JS | MECH GROOVED MECH TEE (THD) | 3″ × 1/2″ – 8″ × 4″ | 400 PSI | UL / FM |
| 3GS | MECH GROOVED MECH TEE (GRVD) | 3″ × 1″ – 8″ × 4″ | 365 PSI | UL / FM |
| 3G — this product | MECH GROOVED MECH TEE (GRVD) | 2″ × 1-1/4″ – 10″ × 4″ | 400 PSI | UL / FM / VdS / LPCB |
| 3JX | MECH GROOVED MECH TEE (THD) | 2-1/2″ × 1″ – 6″ × 2-1/2″ | 300 PSI | UL |
| 3J | MECH GROOVED MECH TEE (THD) | 1″ × 3/8″ – 10″ × 4″ | 400 PSI | UL / FM / VdS / LPCB |
Technical data
| Item | Specification |
|---|---|
| Design standard | ASTM F1548, AWWA C606, ISO 6182-12 |
| Material | Ductile iron ASTM A536 Gr. 65-45-12 |
| Coating | Electrophoretic (std.) — epoxy / hot-dip galvanized optional |
| Gasket | Grade “E” EPDM (fire sprinkler) |
| Sizes | 2″ × 1-1/4″ – 10″ × 4″ (DN50×32 – DN250×100) |
| Approvals | Sizes | Working pressure |
|---|---|---|
| UL / FM / VdS | 2″ × 1-1/4″ – 10″ × 4″ | 300–400 PSI |
| UL | 2-1/2″ × 1″ | 300 PSI |
| UL / FM | 2-1/2″ × 1-1/4″ – 10″ × 4″ | 300–400 PSI |
| UL / FM / VdS / LPCB | 4″ × 2-1/2″ – 8″ × 4″ | 300–400 PSI |
| VdS / LPCB | 5″ × 2-1/2″ | 300 PSI |
| LPCB | 6″ × 2-1/2″ | 300 PSI |
| UL / FM / LPCB | 6″ × 3″ – 6″ × 4″ | 300 PSI |
| Not stated in the table | 8″ × 2-1/2″ | 300 PSI |
Some sizes come in two pipe outside diameters (for example 73.0 and 76.1 mm for 2-1/2″) depending on the pipe standard; select by the actual outside diameter of your project pipe.
Full dimensions for every size (bolts and more) are in the size table at the top of the page.
Hole diameter and position
The hole diameter for each size is in the product table. A smaller hole restricts flow and stops the gasket seating; a larger one weakens the seal. Deburr and clean the edges, and the locating collar must sit in the hole.
Caution
Drill exactly to the table diameter and on the centreline. Never fit a mechanical tee over a weld, a groove or damaged pipe.
Installation steps
- Check that the pipe ends are grooved to the right dimensions to AWWA C606 (roll or cut groove) and are free of burrs, rust and dirt.
- Inspect the gasket and lubricate its outside and lips with the lubricant recommended in the MECH catalogue; never use petroleum-based products with an EPDM gasket.
- Fit the gasket over one pipe end, bring the other end or the fitting into place, and slide the gasket so it is centred between the two grooves.
- Place both housing halves over the gasket so their keys engage the grooves on both sides.
- Hand-tighten the nuts first, making sure each oval-neck bolt sits in its hole, then tighten alternately and evenly to the torque in the MECH installation manual — never exceed it.
The fitting joins with grooved couplings; how the joint is finished (even pad gap or pads meeting) follows the coupling type in the MECH manual.
Full details and bolt torques are in the MECH installation manual among the files on this page.
Common mistakes
- Letting the gasket lip overhang the pipe end or protrude into a groove, so the gasket is not centred on the joint.
- Exceeding the specified bolt torque, which can damage the bolt or the joint.
- Grooves that do not meet AWWA C606 dimensions, or pipe ends that are not square.
- Tightening the nuts on one side only, so the housing tilts and the key does not seat in the groove.
- Using petroleum-based lubricant that damages the EPDM gasket.
Files and ordering
On this page: Product page (catalogue), Product page (catalogue), MECH Grooved Fittings & Couplings Catalogue, Installation & operation manual, Material Safety Data Sheet (MSDS). Add the product to your request list with size and quantity and we send a quotation, or build a submittal PDF for the consultant. Fu-Mech is the exclusive MECH agent in Saudi Arabia.
Frequently asked questions
Do I need to cut the pipe?
No, only drill it to the diameter in the product table. See the guide mechanical tees.
What is the maximum working pressure of model 3G?
Up to 400 PSI depending on size (from 300 to 400). The pressure for each size is in the size table.
Is model 3G UL / FM approved?
Approvals for this model: UL / FM / VdS / LPCB, varying by size as shown in the “Approvals and pressure by size” table above. See also how to verify UL and FM approvals.
What is the gasket material, and does it suit all fluids?
The gasket is Grade “E” EPDM (fire sprinkler). EPDM suits water and sprinkler systems but not oils or petroleum products; for any other fluid check the MECH catalogue or ask us.
Does it suit roll-grooved and cut-grooved pipe?
Grooves are to AWWA C606, rolled or cut; what matters is correct groove dimensions. The difference is explained in the guide roll grooving vs cut grooving.
References
- ASTM F1548 — Standard Specification for Performance of Fittings for Use with Gasketed Mechanical Couplings Used in Piping Applications
- AWWA C606 — Grooved and Shouldered Joints
- ISO 6182-12 — Fire protection — Automatic sprinkler systems — Requirements and test methods for grooved-end components for steel pipe systems
- ASTM A536 — Standard Specification for Ductile Iron Castings
- UL 213 — Rubber Gasketed Fittings for Fire-Protection Service
- FM 1920 — Approval Standard for Pipe Couplings and Fittings for Fire Protection Systems
- MECH catalogue — Grooved Fittings & Couplings — and installation manual
This guide is general information to help with selection. Figures come from the product data on this page and the MECH catalogue; final design is by the project’s approved designer to NFPA 13 and the project specification.
