I just had a look, all appeared fine on the loose grain section, but once I swapped to 25kg sacks, the Weyermann Pilsner wont to Β£0.00.
Interestingly, when I increased the quantity to 3 sacks, it jumped to Β£0.01.
My suggestion would be for safety reasons. If you stop the pump and disconnect the hose from the check valve, gravity will prevent a CFC'full of boiling wort from pouring back potentially over your fingers.