Thor, or should that be Zeus?

[AndrewMawson]

Simple bypass from output to input - just a tap that can be opened gradually and you can set the pressure exactly as you want it. This was standard practice on the main Grundfos 3 kW pumps that circulated water in my Launderettes when I had them - simple gate valve and in that case a pressure gauge. High enough to fill a washing machine PDQ, but not high enough to bust the flexible hoses !