Duty/standby pumps, a filter bypass or switching between tank and mains. The usual fix is two ball valves, a tee and a few nipples, plus a laminated sign telling the next bloke which valve to shut first.
One 3-way ball valve does the same job with a single handle. You can't leave both legs open by mistake, and there are fewer joints to leak.
The catch is picking the right port pattern. Get L port when you needed T port and the system won't do what you want. Here's how Zetco's new 3-way range breaks down.
L Port: Divert One Way or the Other
An L port ball has a 90° passage. The common port feeds one outlet or the other, depending on handle position.
- Duty/standby pump changeover
- Switching a supply between two tanks
- Sending flow through a filter or around it
L port can't connect all three ports at once, which is exactly why you'd choose it for changeovers. One way or the other, never both.
T Port: Divert, Mix or Straight Through
A T port ball has a T-shaped passage. Depending on handle position it can:
- Connect all three ports, for mixing or splitting flow
- Divert the common port to either side
- Run straight through the two side ports
Use T port when you need to blend two supplies or keep flow running straight through with a branch available. Don't use it as a changeover where both outlets must never be open together. In mid positions it can connect more than you intended.
Either way, check the flow diagram on Zetco's spec sheet before you commit. Handle positions differ between makers.
Side Entry vs Bottom Entry
On a standard 3-way, all three ports sit in the same plane: two on the ends and one on the side of the body.
On a bottom entry valve the third port comes out the underside. That suits:
- Pump and filter skids where the supply rises from below
- Manifolds where the branch has to drop down
- Tight layouts where a side port would need extra elbows
Getting the geometry right can save two elbows and a lot of fiddly measuring.
The Range
Brass, AGA approved for gas
- L port, series 2205, 6–50mm
- T port, series 2210, 6–50mm
These have chrome-plated brass balls, PTFE seats and a -10°C to 120°C range. Zetco rates them at 4000 kPa from 8 to 25mm, 2500 kPa at 32–40mm and 1600 kPa at 50mm. Both are listed as AGA approved to AS 4617, so they suit gas changeover duties. They're not WaterMarked, so keep them off potable water.
Brass bottom entry
- L port bottom entry, series 2202, 6–80mm
- T port bottom entry, series 2201, 6–80mm
These are rated 1600 kPa, -10°C to 99°C, and run up to 80mm. Neither is WaterMarked or gas approved, so they're for non-potable water, irrigation, process and skid work.
316 stainless, WaterMarked
- L port, series 4413, 6–50mm
- T port, series 4414, 6–50mm
These have 316 bodies and balls, 4000 kPa and -20°C to 150°C. Zetco lists them as WaterMarked (licence WM-022793). These are the ones for potable water changeovers, plant rooms, food and beverage, and anywhere corrosive.
Choosing by Job
- Potable water pump changeover or tank/mains switch: 4413 L port
- Blending two potable supplies: 4414 T port
- Gas changeover: 2205 L port. Check the arrangement still complies with AS/NZS 5601.1.
- Non-potable skid where the supply comes from below: 2202 or 2201 bottom entry
Install Tips
- Label the ports. Scratch or tag which port is common before the valve goes in. Once lagged, nobody can tell.
- Leave room for the lever swing. Three-way handles travel further than a standard quarter-turn on some patterns.
- Don't use them for throttling. Like any ball valve, they're for on/off and diverting. For regulating flow, see our globe valve guide.
The Short Version
Use L port for changeovers, T port for mixing or straight-through-with-a-branch, and bottom entry when the supply comes from below. Then match the material to the job: brass for gas, 316 WaterMarked for potable water.
You'll find the full range in our ball valves and Zetco collections. Gas isolation is covered in our AGA gas ball valve guide.
Frequently Asked Questions
What's the difference between an L port and a T port 3-way valve?
An L port diverts flow from the common port to one outlet or the other, never both. A T port can also connect all three ports or run straight through, so it suits mixing and splitting flow.
Which 3-way ball valve should I use on potable water?
The 316 stainless L port (4413) or T port (4414). Zetco lists both as WaterMarked. The brass 3-way valves in this range aren't WaterMarked.
Can I use a 3-way ball valve on gas?
The brass 2205 L port and 2210 T port are listed by Zetco as AGA approved to AS 4617. The installation still has to comply with AS/NZS 5601.1.
When do I need a bottom entry 3-way valve?
When the common supply rises from below, as on many pump and filter skids. The bottom port saves elbows and keeps the layout tight.