Fresh water pump..

[DrivingMissLazy]

Richard, that device is called a accumulator tank works like a bladder tank on a well.I have one on my system and think it was a waste of money for the water on demand pumps and a lot of trouble keeping the right air pressure plus I mounted mine where it is hard to check the air pressure but if anyone wants them JC Whinety has one on sale

Thanks, I could not remember the correct name. A senior moment maybe?
I really liked the one I had and it definitely helped. I never needed to check the air pressure as the air bladder was sealed and could not leak air and water could not get into it.

Richard