[JRTJH]

My guess would be that the pump is not priming properly. Possibly a loose clamp on the input to the pump from the water tank? or a kink/hole in the supply hose? Maybe a cracked pump head or a loose bolt/bad gasket on the pump? Don't forget to double check all the fittings on the pump head to make sure they have teflon tape on them.

It sounds like it's not priming, running until it finally gets enough water pulled into the system to "finally pressurize" the lines. Somewhere, air is getting into the lines and most likely, since pressure "AFTER" the pump would cause water leaks and intermittent pump operation, your problem is before the pump.

As for two fresh water tanks, usually they are connected with a upper vent line and a 1" or 1.5" lower supply line.

Keep us posted on what you find.

Good luck !!!!!