This was forever a problem for me.
I looped my power-steering back with a T-piece running up to a filler. Used copper plumbing pipe attached to car chassis, and then flexible pipes to steering pump. Eventually after, say, a 1000 miles, one of the flexible pipes would leak (pinhole?). I also found that heater rubber piping expanded, so I replaced them with proper power-steering rubber pipe.
I had a plumbing tap (isolation valve thingy) as the filler (say 9 inches above the pump) so I left this very slightly open as a breather, and fluid started to leak out of here. So now I keep the tap almost shut, with a plastic isolating diaphragm covering it - with a pinhole in it.
Seems to be ok now.
-steve
(I'll try and get some photos after the bank-holiday if you want).