compression joints from past little jobs ive done dont work very well due to the soft alloy, but there are plastic couplings which you just push the pipe into and they lock and seal,these work very well with diesel, oil. and compressed air and the best part of it you can get them from a plumbers merchant or any auto parts place and if you are desperate and cant find 1 email me and i will send you 1 or 2 cost about 60p each or there abouts,