Water Pumps.......

.....and non-return valves.

I'm trying to find out 2 small facts about my water system (2006 Buccaneer):

1. Whale (Carver Crystal II connection) Submersible Pump in my Aquaroll, connected to the filter housing - is there a non-return valve or method of preventing backflow into the Aquaroll from the internal water system?

2. RK Reich 19 l/min internal (twin motor) tank pump - I've ordered a replacement as I think one of the motors is "goosed" but I don't know if the "integral" non-return valve on the top is removable (there are two types - with and without NRV - I've ordered "with" when I now think I need "without" - ooops!). Anyone know?

Both the Whale and RK sites are very colourful but not technical enough for these details. Anyone help?