For a water project, specify each valve by its type, nominal size, pressure rating, end connection, body and trim material, and the standard it is made and tested to. Then require a pressure test report. Vague orders for 'water valves' are a common cause of leaks and rejected deliveries.
This guide sets out the checklist for waterworks, irrigation and pipeline projects.
Which valve type for which job?
Gate valves isolate a line with low flow resistance when fully open. Butterfly valves are compact and common on large pipes. Ball valves give quick, tight shut-off on smaller lines. Globe valves throttle flow, and check valves stop back-flow. Our overview of gate, globe, ball and butterfly valves from Gujarat describes each.
Air valves, pressure-reducing valves and float valves are also common in water networks. Specify them separately and state the working conditions.
What belongs in the specification?
List these items on every valve line of your order:
- Nominal size and pressure class, matched to the pipe and the maximum working pressure of the system.
- End connections, such as flanged or threaded, with the flange standard and drilling.
- Body material, such as cast iron, ductile iron, bronze or stainless steel, and the trim and seat material.
- Operation: handwheel, gearbox, lever or actuator, and the direction of closing.
- Coating or lining, particularly for buried or potable water use.
Which standards apply?
Different standards cover valve design, dimensions and testing. American, European and British schemes all exist, and a project often names one. Our guide to valve standards API, ANSI and DIN explains the differences. State the standard on the order and confirm the manufacturer actually works to it.
For drinking water, check what material approvals your country requires. Rules on lead content and approved materials vary, so ask your regulator or the water utility.
Also state the direction of operation and the number of turns to close. Mixed conventions between valves on one network confuse operators and lead to damage from over-turning.
What should be tested?
Each valve should pass a shell test, which checks the body for leaks, and a seat test, which checks that it shuts tight. Both are done with water or air at a pressure set by the standard. Our note on hydrostatic pressure tests for valves describes the method.
Ask for the test certificate, and for witnessed tests on a sample of the lot where the project is critical. Also check dimensions, markings and coating on arrival.
How do you avoid problems?
Approve a sample valve before bulk production, including a cut-through look at the casting where possible. Make sure each valve is marked with size, pressure rating, material and a batch number. Pack with end covers to protect flange faces and seats.
Keep the sample as a reference for the whole project. When later lots arrive, compare them with the approved sample for casting quality, weight, finish and markings, and reject those that differ before they are installed in the ground, where a fault is costly to reach.
Next step
We can find valve makers who work to your standard, check samples and have pressure tests witnessed. To start, book a free sourcing review.