Ive got a Rheem Heatpump thats about 2 years old

it was part of the safety recall to do with the pump that was done about a week ago, since then im finding the the pressure valve to be leaking about 40L of water a day

ive called rheem about the problem and they said they wont replace the check valve if there isnt a pressure reducing valve fitted

are they just trying to push the buck or is there some truth to it

also whats the price for a new valve and can you buy them at bunnings