Thanks for the reply, sailor. Yes, I think that is it. Instead of a filter washer,
I have a 10gph flow control which is basically a small hole in a disc which restricts the flow , and a washer around it.
It is connected upstream to an anti-syphon part. The leak is between the
anti-syphon part and the swivel adaptor or possibly it is coming from the anti-syphon part itself. I can't be sure because the flow is so large. I spoke to somebody at the hardware store today who suggested that if the line downstream was blocked, the anti-syphon would start releasing water.
Initially when the leak was much smaller, it was clearly from the junction between the anti-syphon and the swivel adaptor, not from the 1/4" tubing
connection. I don't know why things got so much worse after I unscrewed those 2 parts and put teflon tape on the hose threads. Even when I went back and removed the tape, things were much worse than they were in the beginning.
The other thing I noticed is that the washer around the 10gph flow control didn't seem to fit very well and I'm surprised the initial leak was as small as it was. After I unscrewed it and reinstalled it things were never the same.
I didn't think installing the tape would have cause a blockage downstream
but maybe it did if a piece of the tape broke off.