Hi Anne, you can try just putting it back on and tightening it all up. At worst you might need a new olive. It’s a 22mm fitting which is a standard size and available from any decent plumbers or diy store. When you tighten the joint the olive deforms and grips the pipe and fills all the holes. When it blows off and you put it back on it might be that it’s unable to deform again to fill the spaces in the same way, but very often it will work again. Hope the students have enjoyed it.