We have virtually no water coming out of our shower head. The water coming out of the tub faucet is at normal pressure. when we turn the knob for shower water, the wate pressue goes down to almost nothing (not enough to take a shower, we have to take baths). We have replaced the shower head and it made no difference. We ran a "snake" down the pipe (after removing the shower head, of course) and there seems to be no blockage. Our home is about 30 years old - we bought it nine years ago and have not had this problem before - not in the bathroom or any other room. Any suggestions of what the problem could be?