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Single-port valves — commonly called monovalves or Z valves — provide one regulator connection point on the cylinder neck. They are the standard valve for recreational single-cylinder diving, sidemount cylinders, stage and deco cylinders in technical configurations, and argon inflation cylinders. The range covers standard EN 144 models at 232 bar, a 300-bar variant, nitrox-specific versions with oxygen-compatible seals, a US 3/4″ NPSM thread model for North American regulator compatibility, and a conical E17 thread legacy model.

Products in This Category

Seven single-port valve models are available. The Left Z Valve (SKU 730200) is the standard 232-bar EN 144 monovalve for recreational and sport diving — the baseline configuration used across European dive centres. The Left Z Valve II EN 144 (SKU 733232) is a second-generation body design at the same pressure rating with a revised spindle handle geometry. The Left Monovalve 300 bar (SKU 736300) uses a 7-thread DIN bore and a 300-bar rated burst disc for use with 300-bar cylinders. The Left Z Valve (EN144) Conical E17 (SKU 740200) uses a tapered thread for regulator connection and is intended for legacy regulator compatibility. The Left Z valve 3/4NPSM (SKU 735232) provides a US-market 3/4″ NPSM regulator connection thread for use with North American first stages. The Left Z valve Nitrox 26×2 EU (EN144) (SKU 738201) uses a dedicated 26×2 mm nitrox port thread, the European standard for EAN connections. The Left Z valve Nitrox-G5/8 reg.conn. (SKU 738200) provides nitrox-rated service through a standard G 5/8″ port, functioning as an oxygen-clean standard-connection valve.

Selecting the Right Single-Port Valve

For a standard European recreational diver using a DIN regulator and a 232-bar cylinder, the Left Z Valve (730200) or Left Z Valve II EN 144 (733232) is the appropriate choice — both use the standard M25×2 tank thread and G 5/8″ EN 144 DIN regulator connection. For 300-bar tank configurations, the Left Monovalve 300 bar is mandatory — do not fit a 232-bar valve to a 300-bar cylinder. For cylinders dedicated to nitrox service, select either the 26×2 nitrox valve (if your nitrox regulator uses a 26×2 first-stage connection) or the G 5/8″ nitrox valve (if your nitrox first stage uses a standard G 5/8″ DIN connection). For sidemount, stage, and argon configurations, the standard 232-bar Left Z Valve is appropriate in most cases; 300-bar monovalves are used on 300-bar stage cylinders in technical diving setups.

What to Look For

  • Pressure rating match. 232-bar valves for 200/232-bar tanks; 300-bar valve for 300-bar tanks. Never mix ratings.
  • Regulator connection thread. Standard EN 144 DIN G 5/8″ for most European divers; 3/4″ NPSM for North American regulators; 26×2 for nitrox regulators with a dedicated nitrox port.
  • Nitrox service requirement. If the cylinder will be used for EAN above 21%, the valve must be oxygen-cleaned and rated — select a dedicated nitrox model rather than cleaning a standard valve.

Maintenance and Care

See the Valves category maintenance section for general valve care. For single-port Z valves specifically: the DIN bore O-ring should be inspected and replaced each dive season or whenever it shows compression set or surface cracking. The spindle packing O-ring is the seal that prevents gas from escaping past the valve handle — if bubbles are observed exiting the spindle area under pressure, the valve must be taken out of service until the packing is replaced. Do not operate a valve with a known spindle leak.

FAQ

What does “left” mean in the valve name?

The left/right designation refers to the direction the valve handle projects when the regulator port faces forward (toward the diver’s right shoulder in standard backmount). A left-hand valve has the handle projecting to the left — this is the European convention and is standard for all valves in this range. For single-cylinder recreational diving, all valves should be left-configuration. In twinset configurations, the convention is left valve on the left cylinder and right valve on the right cylinder (right-hand modular valves are available in the Modular valves section).

Is the 300-bar valve DIN compatible with my 200-bar DIN regulator?

Not directly. The 300-bar DIN valve uses a 7-thread bore (deeper); standard 200-bar DIN regulators have a 5-thread insert which does not engage fully in a 7-thread bore. To use a 300-bar DIN valve with a 200-bar DIN regulator, you need either a 300-bar DIN insert for your regulator (if the first stage accepts it) or a DIN 300→200 adapter. Confirm with your regulator manufacturer. Using a 200-bar DIN insert in a 300-bar valve bore is not safe — the insert will not seat correctly and the gas seal is compromised.

What is the 3/4″ NPSM thread and when do I need it?

3/4″ NPSM (National Pipe Straight Mechanical) is the regulator connection thread used on North American market diving valves and regulators, primarily from US manufacturers and for equipment sold in the United States and Canada. It is not compatible with EN 144 DIN G 5/8″ first stages without an adapter. If you are equipping a cylinder for use with North American regulators, or if your first stage specifies NPSM connection, select the 3/4″ NPSM valve (SKU 735232).

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