Hi cjb222,
Welcome to the Heartland Owners Forum and to the family. We have a great bunch of folks here with lots of information and all willing to share their knowledge when needed.
Yes, the check valve on the pump could be leaking or if you have the Anderson valve it could be set wrong or leaking also. What do you have Anderson valve set on? I'm sure some of our other Mallard owners will jump in soon with some help for you.
Be sure and check out our
Heartland Owners Club. Join us at a rally when you can and meet lots of the great folks here and make friends for a lifetime.
Enjoy the forum and your new unit.
Jim M