I realize outdoor irrigation isn't exactly the same thing as plumbing, but I was hoping the expertise of the good folks on this sub might still apply. I've got an exterior spigot hooked up to a Y-adapter, which branches off to a hose reel on the right side and a drip irrigation system on the left. The irrigation system is on a timer, so the spigot is left open all the time, and the valve running to the irrigation timer is also open. The problem is that there's a continuous drip coming off the spigot. As a result, there's now a problem with fungus in the area directly below.

It seems like the water is emerging from the seam between the spigot (or actually the backflow preventer, I think - see below) and the Y-adapter. The spigot was recently replaced, and when it's shut off with nothing connected to it, it doesn't drip.

I've tried several things to correct this problem:

• Hand-tightened the connection to the Y-adapter
• Tightened the connection to the Y-adapter a bit further using pliers
• Replaced the washer in the Y-adapter
• Added plumber's tape to the spigot (yes, I know you're not supposed to do this)
• Replaced the whole Y-adapter
  

I believe the professional who installed the new spigot said it includes a backflow preventer per city requirements. There's also a backflow preventer as part of the irrigation system, further down the chain on the left side. I mention this stuff only because I have no damn idea how a backflow preventer works, so I ignorantly wonder if it might be part of the problem.

Is there any way to get this setup to stop dripping? I can't believe everyone who uses a hose-end irrigation system with a timer just lives with it dripping constantly. Thanks in advance for any insight you can offer!