Valve to AF connection not closed completely. Also means the check valve in your water pump is probably leaking backwards.
Some TT's have two valves on the suction side of the pump; one to the FW tank and one to the AF connection. If you have this, then I'd also say your FW tank valve is closed, otherwise the water would be going to the FW tank instead of out of the AF connection.
Some TT's have a "3 way" valve where you set it to the FW tank or the AF connection. If you have this, then it's in the AF position. Be careful here, because if you want to use the pump with it this way, you'll just suck air from the AF connection instead of water from the FW tank.
Also, if you have the separate valve arrangement, here's an easy way to fill your FW tank. Hook the city water hose to the AF connection and open both the AF and FW valves. Close the AF valve when the FW tank is full. CAUTION: Although this lets you fill the FW tank fairly fast, don't fill it TOO fast. If you go faster than the FW tank's vent can vent off the air, you can blow up your FW tank. Use the AF valve to throttle the flow to the FW tank.
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