Is the pressure in a pipe equal the pressure in the tank?

The pressure can be reduced by gravity and flow. The pressure at a greater height will be larger than than at a lower height (however, if you're dealing with just a gas, you need a large distance for the difference to be significant). Also, when a fluid under pressure is released, some of the internal energy is converted to velocity, reducing the pressure. So when gas is flowing out of the tank, its pressure will be lower than the gas in the tank.