When you say low pressure, I assume you mean low water delivery
pressure at the tap. The water accumulator is set to turn pump off when the correct storage
pressure is reached then turn on as pressure drops when tap opened. Then re-pressure tank when tap closed and the pump turns of again when correct pressure reached.
If the problem was your pump unable to supply the correct pressure it would be running continuously. (possible pump problem) same symptom can be caused by a leak (but then you will have fresh water coming out somewhere)
If the pump can supply correct pressure but the flow is very slow. Once you turn tap off pump eventually switches off. This could indicate a flow issue (blocking filter) but the initial tap flow should be good from the accumulator but then drop of quickly.
Hope this helps you to give us a bit more detail of what is happening.