Four days ago (09/12/2005) I noticed the water had a "rust/metallic" odor while taking a shower. Two days later (09/14/2005) the water started "pulsating". Pump was coming on and shutting off every 1-2 seconds. I replaced the pressure gauge and the 30-50 PSI switch and the water no longer pulsates. It comes on at 30 and shuts off at 50 like it is supposed to do. The problem I am now having is the pressure is dropping without any valves open in the house. I closed the valve at the pump (between the house and the well) and the pressure still drops. I can see all the pipe so I know there isn't a leak at ground level. So I either have a problem with my pump or the tank. I installed a 4" Flotec FP2222-02 3/4HP submersible pump and a Flotec FP7110T-00 tank on 12/26/1998. The pump is dropped 110 feet using single 110 foot black plastic line from the submersed pump to the surface. My question is: Is it possible a bad tank can cause the water to feed back through the line? Or do I have a pinhole leak possibly in the line from the pump to the tank?