I created this for my kids to play with now that the temperature is getting hotter. It could be done cheaper. I spent about $20 on it. This is my first instructable so please bear with me. My trampoline is 14'. I got all my supplies at Home Depot.
Step 1: Assembling tubing
I started with two 10' pieces of 1/2 flexible tubing (I think it is used for sprinkler systems). I connected them together with a little coupling and then duct taped the joint. I bought a plug for one end a adapter that went from the 1/2" to 3/4" (forgot to get a picture of). A water hose they said was 3/4". The problem is that the end of the water hose would have to be threaded into this coupling and so I would have to turn the entire water hose. To get around that I bought a quick release connector in the water hose section that allows me to pop the hose on and off much like a connection on air tools.
Step 2: Test Fit
Next I took my tubing out and strung it across the top of the netting and zip tied it to the poles like I wanted it and then make a few marks so I would know where the sides and bottom were.
Step 3: Attaching Sprinkler Nozzles
I took the tubing back off and down on the deck. I put one nozzle close to the middle and then put four down each side at 16" intervals. I took another piece of pvc pipe and did a test fit with my different drill bits to see what size fit the best. The first couple I wrapped with pink water tape but gave up on that half way through because they were so hard to get in.