In reply to Marion Leister:
Milton will not get rid of calcium type deposits. Vinegar might.
I run cooled boiled water through mine (less mineral content than tap water) or use distilled. Then take the bite valve off, hold tube at end go in garden and swing it round as fast as you can (until it makes a humming noise!). Most of the water will come out and you will not have a problem!
Alternatively... the plastic tube is cheap to buy, 50p a metre or something. Find a supplier, buy a few metres to last a while, cut to suit and replace every so often. A lot cheaper than buying the platy kit.
I'll try and track down a supplier that is online.....