Non return valve

[bikerwookie]

Our motorhome has a non return valve just after the pump. It restricts the flow quite a bit. It’s currently 12mm on to a new whale high flow pump and the wiring is good with minimal voltage drop. Any recommendations for a better non return valve with less restriction?

 

[Spriddler]

Not easy to suggest a different one without a pic of the one you have.
Is it caused by the NRV or a constriction up or downstream of it?

 

[bikerwookie]

No restriction down stream and the pump flows very well without the valve.