Grooved elbows change the direction of fire protection and water pipework and are joined with grooved couplings, without welding. They come in 90°, 45°, 22.5° and 11.25°, and reducing elbows change size and direction in one fitting. This guide helps you choose the right elbow and read its size table.
Key points
- Every grooved elbow needs two grooved couplings of the same size and OD.
- Small angles (22.5° and 11.25°) suit minor offsets and getting round obstructions.
- A reducing elbow saves a fitting by changing direction and size at once.
- Pressure varies by model and size; check the product table.
Available angles
| Model | Angle | Sizes | Working pressure (by size) |
|---|---|---|---|
| 90 | 90° | 1″ – 24″ | 500 / 300 PSI |
| 90S | 90° | 2″ – 8″ | By size |
| 90X | 90° | 3″ – 12″ | 300 PSI |
| 120 | 45° | 1″ – 24″ | 500 / 300 PSI |
| 120X | 45° | 3″ – 10″ | 300 PSI |
| 110 | 22.5° | 1-1/4″ – 8″ | 500 PSI |
| 110X | 22.5° | 4″ – 6″ | 300 PSI |
| 105 | 11.25° | 1-1/4″ – 8″ | 500 PSI |
| 90R | 90° reducing | 3″ × 2-1/2″ – 6″ × 4″ | 500 PSI |
All are ductile iron ASTM A536 Gr. 65-45-12 to ASTM F1548, AWWA C606 and ISO 6182-12; approvals (UL / FM / VdS / LPCB) vary by size in each model’s table.
How to choose the right elbow
- Establish the change of direction required on the drawing.
- State the nominal size and the pipe OD in millimetres.
- If the size changes at the same point, consider a reducing elbow instead of a separate elbow and reducer.
- Check working pressure and approval for that size.
- Count the couplings: two per elbow.
Caution: outside diameter
Some sizes have more than one OD in the MECH tables, such as 6″ at 165.1 or 168.3 mm. The elbow and couplings must match the actual pipe OD on the project.
Elbows and pressure loss
Each elbow adds friction loss, usually counted in hydraulic design as an equivalent length of straight pipe. A 90° elbow adds more loss than a 45°. Designers therefore keep elbows and unnecessary changes of direction to a minimum, taking the values used from the code and the manufacturer’s data.
Common mistakes
- Ordering by nominal size only, without the OD.
- Forgetting to count the couplings with the elbows.
- Using two elbows in a row where a reducing elbow or a suitable angle would do, adding loss and cost.
- Choosing a model not approved for the size required in a fire system.
Frequently asked questions
Can two 45° elbows replace one 90°?
Yes, where a gentler route or getting round an obstruction calls for it, bearing in mind that each fitting needs extra couplings and counts in the hydraulic loss.
When would I use an 11.25° elbow?
For very small offsets, such as shifting a line slightly to clear an obstruction or match a slight slope.
Are grooved elbows acceptable in sprinkler systems?
Yes, when they are listed and approved for the size and pressure required and joined with approved couplings.
References
- NFPA 13 — Standard for the Installation of Sprinkler Systems.
- ASTM F1548 — Performance of Fittings for Use with Gasketed Mechanical Couplings.
- AWWA C606 — Grooved and Shouldered Joints.
- ISO 6182-12 — Grooved-end components for steel pipe systems.
- UL 213 — Rubber Gasketed Fittings for Fire-Protection Service.
This guide is for technical awareness and does not replace the manufacturer’s data sheet or the requirements of the project’s approved designer.
