likely have an accumulator in the mix. If you do and you drained the water out, when you refilled it have been left with no air in it. If that's the case and your pressure switch may not operate. Drain the water out of it be removing the hose at the bottom. There may be a vent hole in the top of the tank. I've seen them with and without them. I would highly suggest that you removed the accumulator and pump and replace it with one of the new style pump systems. The Jabsco Par-Max 2X Water Pressure System Pump is the one I use and it supplies water to both the galley and head with plenty of water pressure to shower. I would suggest that you remove the old pump and install a two position terminal block in a convenient position and lay the old wires down onto it with ring terminals. I would mount the new pump and connect it to the terminal board with ring terminals as well. Apply some grease to keep the moisture off the connections and your maintenance in the future will be much easier. The new pump systems don't need the accumulator so you gain some room. Usually under the sink. They use the pump RPM speed to control flow and the noise lever is very low.