fresh water not flowing

First boat, steep learning curve, this forum is incredible! The water pump pressurizes sufficiently for main sink and head sinks but the showers and outside handheld deck shower offer a mere trickle, any insights welcome.

Our 1985 Catalina 30 mk I has two fresh water tanks, one forward under the vberth and the other under the port settee. I can get water out of the port side tank, but not from the forward tank. I found a 'T' under the aft quarter berth next to the fuel tank. No water comes out of the side I...