Originally Posted by Njg
I just realized the AI comes with a built-in water pressure regulator. I had always used a regulator at the shore water hookup, this may explain my low pressure. Does everyone trust the built-in regulator or does the group also use an additional external regulator?
These things aren't dividers, so having two won't significantly impact your pressure unless one of them is doing a poor job. The built-in regulator reduces the pressure to I think 55psi (same pressure that the internal pump runs at). If your water pressure at the faucets is OK when disconnected from city supply, but too low when connected (and pump off), then either the city supply pressure is low (turn your pump on to assist), or your external regulator is doing a poor job. If you really want peace of mind, purchase and use a high quality adjustable pressure regulator, connect it to the city supply bib, and set it to 55psi. Job done.
P.S. To answer your question, I always use an external regulator just because I have it and have always used one. I can see cases where insanely high city pressure could overwhelm the built-in regulator (potentially causing a leak), so I will continue to use the external regulator at the city hookup. FWIW, I also have a "Y" after my regulator so I have a sane flow rate for external use and black tank flush (which has a back-flow preventer inline....).