Water networks in buildings, facilities and cities need valves for isolation, preventing backflow, pressure control, and protection from debris, air and vibration. This reference guide covers each function, when each type is chosen and what to check in the specification, with the MECH blue range models designed for water.
Key points
- Isolation valves: gate valves (NRS and OS&Y) for full isolation, butterfly valves for large sizes and tight spaces.
- The MECH blue range is rated 300 PSI in most models and coated internally with FBE epoxy to AWWA C550.
- The Z45X valve carries NSF approval per its product page.
- Check the flange pattern: most models are ASME B16.1 CL125, and the pressure control valves EN 1092-2.
Isolation valves
A gate valve gives a full, unobstructed bore when open and seals tightly when closed, making it the usual choice for isolation. A resilient wedge to AWWA C515 leaves no cavity at the bottom for sediment to collect. NRS is shorter and suits rooms and buried service; OS&Y shows its position at a glance. See the comparison. A butterfly valve is lighter and shorter, suiting large sizes and flow control.
Check valves
They stop water flowing back when a pump stops or pressure falls. The flanged swing check (AWWA C508) suits horizontal lines and normal pressures; the wafer type is shorter and lighter between two flanges. See the check valves guide.
Pressure control
A pressure reducing valve holds outlet pressure at a set value whatever the inlet pressure, and is used to divide towers into pressure zones. A relief valve opens above a set pressure to protect the network. See the difference between them and pressure ratings.
Protection: strainers, air and vibration
- Y-strainer ahead of pressure valves, meters and pumps. See the strainer guide.
- Air release valve at high points to expel trapped air, which reduces flow and causes water hammer.
- Rubber joint at pumps and equipment to absorb vibration and movement. See the flexible joints guide.
MECH models for water
| Function | Type | Model | Standard / flange | Sizes |
|---|---|---|---|---|
| Isolation | NRS gate valve | Z45X | AWWA C515 · NSF | 2″ – 24″ |
| Isolation | OS&Y gate valve | XZ41X | AWWA C515 | 2″ – 24″ |
| Isolation and control | Wafer butterfly valve | D371X205 | MSS SP-67 | 2″ – 24″ |
| Check | Flanged swing check | H44X2 | AWWA C508 | 2″ – 12″ |
| Check | Wafer check | DH77X | — | 2″ – 18″ |
| Protection | Y-strainer | V4 | — | 2″ – 12″ |
| Pressure | Pressure reducing | SK720X | PN10 / PN16 / PN25 | 2″ – 24″ |
| Pressure | Pressure relief | SK730X | PN25 | 2″ – 12″ |
| Air | Air release | ARVX | — | 1/2″ – 1-1/2″ |
| Vibration and movement | Flanged rubber joint | XTQ1RF | ASME B16.5 CL150 | 1-1/4″ – 24″ |
What to check in the specification
Warning
Potable water needs materials and coatings approved for contact with drinking water, as the network operator requires. Check the approval needed (such as NSF/ANSI 61) on each model’s page before submitting it; not every model carries the same approvals.
- Rated working pressure against the highest network pressure.
- Flange pattern against the mating flanges. See flange compatibility.
- The manufacturing standard the specification requires (AWWA or EN).
- Internal coating and drinking-water approval where needed.
Frequently asked questions
What is the difference between MECH red and blue valves?
Red valves are for fire protection and UL listed or FM approved; blue valves are for general water networks.
Can a butterfly valve be used for isolation?
Yes, and it is common in large sizes, bearing in mind its disc stays in the waterway.
Where is an air release valve installed?
At high points of the line and after pumps, where air collects.
References
- AWWA C515 — Reduced-Wall, Resilient-Seated Gate Valves for Water Supply Service.
- AWWA C508 — Swing-Check Valves for Waterworks Service.
- AWWA C550 — Protective Interior Coatings for Valves and Hydrants.
- MSS SP-67 — Butterfly Valves.
Model data is from MECH product pages; final selection rests with the designer and the network operator’s requirements.
Part of a complete guide
This article is part of Approving Fire Protection Materials in Saudi Arabia: From the Consultant to Civil Defense.
NWC approved
