How to Fit a Brass Non-Return Valve (NRV) the Right Way
A non-return valve (NRV), also called a check valve, lets water or oil flow in one direction only. When the flow tries to reverse, the valve closes by itself. It is fitted where back-flow would cause trouble, for example on a pump delivery line or a line feeding a tank. An NRV only works well when it is fitted on the right line and the right way round.
1. Use it on horizontal lines only
The M-Tech forged brass NRV is a horizontal NRV. Fit it on horizontal pipe runs only. Do not fit it on a vertical line.
2. Follow the flow arrow
Every NRV body has an arrow cast or marked on it. The arrow must point in the direction the water should flow, away from the source (for example, away from the pump). Fitted the wrong way round, the valve will block the line.
3. Use it for the right medium
The M-Tech horizontal NRV is for water and oil, up to 80°C. Do not use it on gas, air or steam lines.
4. Match the size and thread
Choose the same size as the pipe. M-Tech horizontal NRVs come in 1/2", 3/4", 1", 1-1/4", 1-1/2" and 2". Threads are to the IS 554 / BS 21 / ISO 7 pipe thread standard, so they fit standard threaded pipes and fittings. Read more in our guide IS 554 vs BS 21 pipe threads.
5. Fit it cleanly
- Flush the pipe first so dirt does not sit under the valve.
- Wrap PTFE tape on the male threads.
- Hold the valve body with a spanner while you tighten, so the body is not twisted.
- Open the water slowly and check the joints for leaks.
Quick checklist
| Check | Right |
|---|---|
| Line direction | Horizontal only |
| Arrow | Points the way the water flows |
| Medium | Water or oil, up to 80°C |
| Not for | Gas, air, steam, vertical lines |
| Size | Same as the pipe, 1/2" to 2" |
Need help choosing?
Send the pipe size and the line it is for on WhatsApp at +91 77550 01116, or visit www.m-techvalves.com. Forged Brass • Made in Jamnagar.