PVC fittings for irrigation have tapered threads. They are really tight
after a couple of turns. Make sure you get the adapter for hose fitting.
That adapter has no taper. It should tighten easily by hand.

REBEL JOE wrote:

I got a new waterfall that has a bulkhead fitting on it. I got a male
fitting to reduce the size to my water hose and it screws in by hand
real easy about 1/2 way then it gets hard. Do you use a wrench to
tighten it all the way? Is it supposed to be tight like that? Should
threads still be showing after its tight? They are PVC fittings. I know
I have to use teflon tape also. As you see I'm no plumber.

http://community.webtv.net/rebeljoe/POND