N.R. Valves:

Enter Number of Non-Return Valves. Sometimes called Reflux, Check, one-way valves. Friction loss varies substantially between actual types of valves, but a value of 1 should be close enough for industrial valves around 50mm, smaller valves will require a value around 2 (small poly loaded poppet type valves may be similar to a value of 6?) For larger valves around 300 mm, a value of 0.7 per valve could be used. Add these together and enter in the text box.