Jason b, its a very nice idea, but i can not do that with hand tools, and i dont have a lathe.
BUT, vaguely based on that idea, i have solved the problem. so a big thanks to all.
For those that want to know, i did the following:
MK1
Drill 4 holes paralell to each other, but both on the same plane. insert a brass bolt through each hole on one side, and bolt exits at hole directly opposite it.
Looking down the pipe you see 2 bolts side by side. place nut with bolt on "bridge" of the first 2 bolts, solder nut in position.
undo bolt securing nut on bridge. Er, undo bolt securing nut on bridge, can't undo bolt
heat vertical bolt to remove nut and bolt
excees solder has run down bolt soldering nut to it.
re solder new nut on bridge, nut falls off bridge down pipe Damn!
give up
MK2
Get 15mm copper pipe, solder on "stop end" drill hole in stop end tap stop end to bolt diameter.
Get 22mm pipe drill 3 holes in side at aprox 120 degrees apart.
tap holes for bolts
screw bolt in each hole
drop 15mm pipe into 22 mm pipe, stop end sits on 3 bolts
tighten bolts
screw another bolt with a large disc into stop end
connect to pump and test
nothing happens
undo central bolt with disk
get soaked
water going wrong way (it is following schamfered edge of disc)
remove bolt turn disc up other way
re-test
well it works, but not as well as i had hopped, but to complete the project i need to make 3 more