Valve End Connections: Flanged, Threaded, Welded, Wafer & Lug Explained
The end connection is how a valve attaches to your piping. It affects pressure rating, cost, ease of maintenance and leak-tightness. This guide explains the main types — flanged, threaded, socket weld, butt weld, wafer and lug — and when to choose each.
1. The main connection types at a glance
| Connection | How it joins | Typical size | Pressure |
|---|---|---|---|
| Flanged | Bolted flange + gasket | 1/2" – 60"+ | Low to very high |
| Threaded | Screws onto pipe thread | 1/2" – 2" | Low to medium |
| Socket weld | Fillet weld into socket | 1/2" – 2" | High |
| Butt weld | Butt weld to pipe | 1/2" – 60"+ | High to very high |
| Wafer | Clamped between flanges | 2" – 60"+ | Low to medium |
| Lug | Bolted to flanges via lugs | 2" – 48" | Low to medium |
2. Flanged connections: versatile and easy to maintain
Flanged valves have bolted flanges on each end that join to mating flanges with a gasket. This is the most common connection for larger valves.
Pros: easy to install and remove, handles high pressure, works across many sizes.
Cons: heavier, more expensive, needs proper gasket selection to avoid leaks.
3. Threaded connections: simple and economical
Threaded valves screw directly onto the pipe end. They are fast and cheap to install.
Pros: low cost, quick installation, no welding.
Cons: limited to small sizes (≤2") and lower pressure; threads can leak if not properly sealed.
4. Welded connections: leak-proof and permanent
Socket weld (small sizes, high pressure): the pipe fits into a socket and is fillet-welded.
Butt weld (larger sizes, high pressure/temperature): the pipe is butt-welded to the valve end for a smooth, strong, leak-proof joint.
Pros: very strong, no gasket to leak, ideal for high-pressure and high-temperature service.
Cons: permanent — valve cannot be removed without cutting the pipe.
5. Wafer and lug connections (butterfly valves)
Wafer: the valve body is clamped between two flanges using long bolts. Compact and economical — the most common butterfly valve connection.
Lug: the valve has threaded lugs so it can be bolted to the flanges. It can be removed from one side without disturbing the opposite pipeline — ideal for end-of-line service.
6. How to choose the right connection
- Large size or high pressure? → Flanged or butt weld.
- Small size, low pressure, low cost? → Threaded.
- Permanent, high-integrity joint? → Socket/butt weld.
- Butterfly valve, compact and economical? → Wafer; choose lug if you may need to remove it.
Frequently Asked Questions
What is the difference between flanged and threaded valve connections?
Flanged uses bolted faces with a gasket — easy to remove and handles higher pressure. Threaded screws into the pipe — cheaper and faster but limited to smaller sizes and lower pressure.
When should I use a welded valve connection?
Use socket weld for small sizes and high pressure, and butt weld for larger sizes and high-pressure/high-temperature service. Welded joints are permanent and leak-proof.
What is the difference between wafer and lug valve connections?
Wafer is clamped between flanges with long bolts (compact, economical). Lug has threaded lugs so the valve bolts to flanges and can be removed without disturbing the pipeline.
Which valve end connection is best?
It depends on size, pressure, removability and budget. Flanged for large/high-pressure and easy maintenance; threaded for small low-pressure; welded for permanent high-integrity; wafer/lug for butterfly valves.
Need a valve with a specific end connection?
Tell us your size, material, pressure and connection type. We supply flanged, threaded, welded, wafer and lug valves.
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