Every plumber has seen it: a ball valve half-closed to balance a circuit or tame a hot water loop. It works for a while. Then the seats chew out from the high-velocity flow across them, and it neither throttles nor isolates properly.
Ball and gate valves are built to be fully open or fully shut. When you actually need to regulate flow, you want a globe valve.
Zetco's new range covers bronze and 316 stainless, threaded and flanged. Here's how to pick one.
Why a Globe Valve Throttles Properly
In a globe valve the flow turns through the body and passes up through a seat. A disc on the end of the stem closes down onto that seat.
Turning the handwheel moves the disc a small, controllable distance, so you get fine, repeatable adjustment across the whole range. The seat and disc are designed to take the wear of partly open service.
The trade-off is pressure drop. The flow path isn't straight, so a globe costs more head than a full-bore ball or gate. That's why they go where you need control, not on every isolation point. For straight isolation, see gate valves vs ball valves.
Globe valves are directional, so install them with the flow arrow.
Bronze, WaterMarked: Threaded 6–80mm
All four of these are listed by Zetco as WaterMarked to AS 1628 (licence WM-020284). They have female BSP ends and suit potable water as well as steam.
- Series 2010, screwed bonnet, metal disc, 15–50mm. 2500 kPa water, steam to 1050 kPa @ 186°C. The everyday choice.
- Series 2018, union bonnet, PTFE disc, 6–50mm. The soft disc gives bubble-tight shut-off and smooth control on potable water. Low-pressure steam only, to 300 kPa.
- Series 2015, union bonnet, stainless trim, 6–80mm. 4000 kPa water, steam to 2400 kPa @ 225°C. The heavy-duty option for high-pressure water and real steam work.
- Series 2014, screw down non-return (SDNR), 10–50mm. It throttles like a globe, and the disc also lifts with flow and seats on reversal. One valve regulates and stops backflow on boiler feeds and pump discharges.
Screwed vs Union Bonnet
- Screwed bonnet: the bonnet threads straight into the body. It's simple and cheaper, and fine for general service.
- Union bonnet: a separate union nut clamps the bonnet on. It resists leaking under pressure and temperature cycling better, and the valve is easier to strip for inspection without the bonnet thread galling.
If the valve will see frequent adjustment, thermal cycling or steam, the union bonnet is worth paying for.
Metal vs PTFE Disc
- Metal disc: handles heat, steam and some grit without deforming. It's the choice for steam and higher temperatures.
- PTFE disc: seals tighter at shut-off and throttles smoothly, but it has temperature limits. It's best on potable water and low-pressure steam.
316 Stainless: Process and Corrosive Lines
The series 2011 heavy pattern 316 globe is investment cast 316 with a metal disc, rated 3200 kPa from -20°C to 200°C, 6–65mm.
It suits process water, chemical and steam lines where bronze won't hold up. Zetco lists it as not WaterMarked, so keep it off AS/NZS 3500 installations.
Flanged Globe Valves
- Series 4631, 316 stainless, ANSI 150, 15–200mm. It has a bolted bonnet, an external screw and yoke, and adjustable stem packing. Zetco lists 15–100mm as WaterMarked to AS 1628, while 125–200mm are not.
- Series 2020, bronze, flanges drilled to order, 20–80mm. Metal disc for steam and heating. Not WaterMarked.
The external screw and yoke on the 4631 keeps the stem thread out of the flow. You can also see at a glance how far open the valve is, which is handy when balancing.
Where They Go
- Hot water flow and return balancing: 2018 or 2010
- Steam lines and boiler work: 2015 (union bonnet, stainless trim) or 2010
- Boiler feed or pump discharge needing regulation plus non-return: 2014 SDNR
- Process or chemical lines: 2011 316
- Flanged hydronic or commercial plant: 4631
The Short Version
Use a globe valve wherever you need to regulate, not just isolate. Choose bronze for potable water and steam, 316 for process lines, union bonnet where it'll be worked hard, and a metal disc for heat.
Browse the range in our hydronic and HVAC valves and Zetco collections. For fine control on small lines, see needle valves.
Frequently Asked Questions
Can I throttle with a ball valve instead of a globe valve?
It's not recommended. Ball valves are made for on/off duty, and running them part-open wears the seats so they no longer seal. A globe valve is designed to throttle.
What does SDNR mean on a globe valve?
Screw down non-return. The valve throttles like a normal globe, and the disc also seats automatically if flow reverses, so one valve both regulates and stops backflow.
Are Zetco bronze globe valves WaterMarked?
Zetco lists the threaded bronze 2010, 2014, 2015 and 2018 series as WaterMarked to AS 1628. The 316 threaded 2011 and the bronze flanged 2020 are not.
Union bonnet or screwed bonnet?
Union bonnet for frequent adjustment, steam or thermal cycling, since it seals better and is easier to service. Screwed bonnet is fine for general, lighter-duty service.