I have been nagged for a while by my son to build a water bottle rocket.
My son has made a video of progress so far. We have mastered a pressure system and pipes. We need to now make a stable base and sort out a release mechanism.
It certainly goes with a big bang when the bottle losses grip on the tube.
We have used a bike tyre valve, garden hose and various pipe fittings to get a 22mm launch tube (needed to reduce the 22mm down a little with sand paper and wire wool).