The usual story: a pump set goes in with whatever check valve was on the shelf. Six months later the customer complains about a bang every time the pump stops, or the pump keeps losing prime.
Nine times out of ten it's the wrong type of check valve for the orientation or the duty.
Check valves aren't interchangeable. Spring, swing and lift types each have a place. Zetco's range now covers all three in bronze, DZR and 316 stainless, threaded and flanged. Here's how to choose.
One thing first: a check valve isn't a testable backflow prevention device. Where AS/NZS 3500 calls for backflow protection, see dual checks vs testable backflow devices.
Spring Check: Fast Closing, Any Orientation
A spring holds the disc against the seat and flow pushes it open. When flow stops, the spring shuts it before the water column can reverse and slam.
- Pros: fast closing, so less water hammer. Most fit in any orientation and are compact.
- Cons: the spring costs some pressure to open, so there's more pressure loss than with a swing check.
It's the go-to for pump discharges that bang, vertical lines and tight spaces.
- Lead free DZR spring check (3907), 15–80mm, WaterMarked to AS 1628. The everyday potable option.
- 316 spring check (1947), 6–32mm, WaterMarked to AS 1628
- 316 spring check, metal jumper (1957), 15–25mm, WaterMarked, 4000 kPa
- 2-piece 316 spring check (1940), 6–50mm, 6300 kPa, any orientation. Not WaterMarked, so it's for process, compressor and industrial lines.
- 3-piece 316 spring check (4020), 6–100mm, 6300 kPa, up to 230°C. The centre comes out for inspection without disturbing the pipework. Not WaterMarked.
Swing Check: Full Bore, Low Loss
A hinged disc swings open with flow and falls closed when it stops. The bore is clear, so pressure loss is low.
- Pros: minimal pressure drop, handles some debris and suits larger flows.
- Cons: slower to close, so it can slam on pumped systems. It also needs the right orientation, typically horizontal lines.
Use it on gravity and low-head systems and horizontal pump discharges where pressure loss matters more than hammer.
- Lead free DZR swing check (3802), 15–100mm, WaterMarked
- Bronze swing check (1805), 15–100mm, WaterMarked to AS 1628. 2500 kPa water, steam to 1050 kPa.
- 316 swing check (4055), 10–80mm, WaterMarked to AS 1628, 3200 kPa, -20°C to 200°C. For corrosive and pool services.
Lift Check: Steam and Hot Water
In a lift check, the disc lifts vertically off a seat, much like a globe valve body. They're robust and seat well, and they're common on steam and hot water.
- Bronze lift check, screwed bonnet (1806), 15–50mm, WaterMarked, water and steam
- Bronze lift check, union bonnet, 316 trim (1807), 15–50mm, WaterMarked, 4000 kPa
- Bronze vertical lift check (1809), 15–50mm, WaterMarked, for vertical lines
Check orientation on the spec sheet. Horizontal and vertical lift checks aren't interchangeable.
Flanged Check Valves
- 316 flanged swing check, Table E (4640) and ANSI 150 (4641), 25–200mm, WaterMarked to AS 1628
- Bronze flanged swing check (1808), 50–100mm, WaterMarked, with flanges drilled to order
More on flange drilling in our flanged plant room valve guide.
Choosing Quickly
- Pump discharge that bangs on stop: spring check
- Vertical line, or no room to get the orientation right: spring check
- Horizontal, low head, pressure loss matters: swing check
- Steam or high-temperature hot water: lift check (1806/1807) or 4020
- Corrosive, pool or coastal: 316 (1947, 4055, 4640/4641)
- Potable water: stick to the WaterMarked models
Fit a Y strainer upstream where debris could hold a disc open. See Y strainers compared.
The Short Version
Use spring checks to stop hammer or for any orientation, swing checks for low loss on horizontal runs, and lift checks for steam and hot water. Pick the material for the water, and check the WaterMark listing for potable work.
Browse the range in our check valves and Zetco collections.
Frequently Asked Questions
What's the difference between a spring check and a swing check valve?
A spring check uses a spring to close the disc quickly, which reduces water hammer and allows most orientations. A swing check uses a hinged disc for a full bore and low pressure loss, but it closes more slowly and needs the right orientation.
Why does my pump bang when it stops?
Often it's a slow-closing check valve letting the water column reverse before it seats. A fast-closing spring check usually cures it.
Is a check valve a backflow prevention device?
Not in the AS/NZS 3500 sense. Where backflow protection is required, use the appropriate rated device, such as a dual check or a testable device.
Which Zetco check valves are WaterMarked?
Per Zetco's listings: the DZR 3907 and 3802, the 316 1947, 1957 and 4055, the bronze 1805, 1806, 1807, 1808 and 1809, and the flanged 4640/4641. The 316 1940 and 4020 aren't WaterMarked.