5 foot head should be plenty to fill a ball valve cistern. I have one working at a foot less than that - although the pipe length is short.

You can't get no flow out of a hose if there's a fall - my garden hose empties very quickly on less than a foot fall over 100 feet. Pressure drop only comes into effect when there's flow, and therefore only restricts the flow - it can't stop it.

So, the problem is in your 1/2 pipework or in the ball valve.

1. Could you have an airlock in the pipework? If it rises all the way to the valve this shouldn't be the problem.

Most UK ball valves come with alternative inserts for high/low pressure. These are very sophisticated - small hole for high pressure, big hole for low pressure. The bigger the hole covered by the seal washer, the better your system will work.

2. Is the valve open when the ball is at the low position? I have known the rubber washer to stick to the valve, and sometimes the linkage is loose enough to allow the ball to drop without opening the valve - water pressure normally solves the problem. You can check this by blowing through the pipework (disconnect the garden hose first!).

If you've got flow at the end of the hose, your pipework rises all the way from here to the valve, and the pipework/valve is clear, the system must work - maybe slowly, but it must work.

Phil