There are two ways to put an isolation valve into a Standard Press 316 stainless line:
- The 316 stainless 3-piece press ball valve, press x press, 15mm to 108mm.
- The 316 stainless 3-piece full-bore ball valve with female BSP ends, DN15 to DN50, fitted with two male BSP press adaptors.
Both are 3-piece bodies, so the centre section can be serviced in line. Here's how they compare on price and on the job.
The price comparison
| Line size | Press valve | Threaded valve + 2 male adaptors | Press valve saves |
|---|---|---|---|
| 15mm (DN15, 1/2") | $59.99 | $51.21 + 2 x $13.93 = $79.07 | $19.08 |
| 22mm (DN20, 3/4") | $84.46 | $63.65 + 2 x $22.06 = $107.77 | $23.31 |
| 28mm (DN25, 1") | $123.29 | $77.77 + 2 x $29.37 = $136.51 | $13.22 |
| 35mm (DN32, 1-1/4") | $179.54 | $128.43 + 2 x $37.99 = $204.41 | $24.87 |
| 42mm (DN40, 1-1/2") | $235.18 | $160.03 + 2 x $53.64 = $267.31 | $32.13 |
| 54mm (DN50, 2") | $319.24 | $246.68 + 2 x $62.98 = $372.64 | $53.40 |
Prices inc GST at time of writing. On parts alone, the press valve is cheaper at every size, and it also saves two threaded joints you'd otherwise have to seal and tighten.
Why you'd still choose the threaded valve
- Full bore. The threaded valve is listed as full bore for minimal pressure loss. The press valve listing doesn't state its bore, so if pressure drop across the valve matters on a long or marginal run, the threaded valve is the known quantity.
- The valve can come out whole. With threaded ends you can unscrew and replace the entire valve body. A press valve is permanently in the line; it's serviceable, but replacing the body means cutting it out.
- Mixed systems. If one side of the valve is threaded equipment, the threaded valve can screw straight onto it, saving one of the two adaptors.
Why you'd choose the press valve
- Cost and labour. Cheaper parts, two fewer threaded joints, and it goes in with the same tool and jaws as the rest of the line.
- Bigger sizes. The threaded valve stops at DN50. The press valve continues to 76.1mm, 88.9mm and 108mm (there's no 66.7mm press valve).
- No thread galling. Stainless threads can gall when tightened; fewer threads, fewer chances.
Where to put isolation valves
- Either side of anything that will be serviced: pumps, PRVs, strainers, meters, filters and backflow devices, so they can be isolated without draining the system.
- At branch take-offs to each zone or floor.
- Pair the valves with a union or flange so the equipment can actually be removed once it's isolated. See unions in stainless press and stainless press flange adaptors.
Check before you install on drinking water or gas
The press valve listing states AS/NZS 4020 compliance for potable-water contact materials, and the threaded valve listing asks you to confirm WaterMark status and pressure rating with PSA before installing on potable water or gas. Do that before you specify either valve on a drinking-water or gas service. For gas, also see the seal caveat in choosing stainless press seals.
For copper press lines, we cover handle and body choices in press fit ball valves: butterfly, lever, extended or union.
Frequently Asked Questions
Is a press ball valve cheaper than a threaded ball valve with adaptors?
In the Standard Press 316 range, yes, at every size from 15mm to 54mm. The saving runs from $13.22 at 28mm to $53.40 at 54mm on parts alone.
Is the stainless press ball valve full bore?
The listing doesn't state the bore. The threaded 316 3-piece valve is listed as full bore.
Can a 3-piece press ball valve be serviced?
Yes. The 3-piece body lets the centre section be serviced in line. Replacing the whole body means cutting the valve out.
What's the largest stainless press ball valve?
108mm. The press valve comes in 15, 22, 28, 35, 42, 54, 76.1, 88.9 and 108mm. The threaded full-bore valve stops at DN50.