Shane-Come Back wrote:
Do you have a recommendation for brand/model?
As already stated, it seems impractical to really meet the goals you have expressed while using the 12V pump and fresh water tank. However, the minimum improvement would be to add one of these
Shurflo tank. However it is only designed to minimize surging as it holds less than one gal. of water. If you want to maintain flow rate on say two faucets for a few minutes, then a larger capacity pressure tank would be needed, something around 2-5 gallons. There are plenty of small vertical tanks and Amtrol makes several horizontal tanks that would be easier to mount. There are probably other brands with horizontal tanks as well.
Hopefully someone with better knowledge can chime in, but I don't see the value of a 7 GPM pump if the inlet pick up tube can't sustain that flow rate.