This could be a number of things. It could be that the pipe is not big enough from the feeder tank - it should be 22mm minimum, this should give you enough flow pressure to the cylinder. It also depends on the amount of head between the cylinder and the feed tank. It could be that your pipework could be crudged up if you are in a hard water area and the pipework is the old iron pipes, this should not be a problem if you have copper pipework. The only tap that should be direct off the mains is the cold water in the kitchen - drinking water, all the other taps in the house (cold) should be off the main feeder tank. Also, make sure that you have the correct fittings for high pressure in the taps, although this should not be a problem. As a last resort, connect the cold tap on the bath to the hot tap on the bath and open both fully, if you have an air lock this will remove it.
Richard
October 2012