How do I stop the seepage leak on a compression fitting and cap?

I have a pigtail of 1/4" copper tubing that I have to cap. The tubing comes out from a saddle valve attached to the copper pipe that feeds my bathroom sink. The house is plumbed with copper tubing and solder, so I can't just unscrew a length of pipe here. I have an inline brass connector with compression fittings on either end. I have attached one of the compression ends to the copper tubing and have capped the other end with a brass cap for compression fittings. I put Teflon tape on the threads of the cap end, but only used the compression fitting (nut and ferule) on the other. I still get seepage from that fitting, no matter how tight I crank down the connection and cap. Last night, I cranked it down even tighter on both ends -- compression and cap -- and it actually leaked seepage faster (one drop of water every minute or two -- I haven't timed it). What am I doing wrong? How can I make the fitting water tight? Or do I have another choice for capping the tubing?

Public Comments

1. tighten it
2. this is not difficult 1 turn off the water 2 get a tube cutter and remove the old end 3 get a new 1/4 inch copper cap and soldier in place 4 done
3. this how its done!!!!!! shut off the water feeding said pipe. drain pipe at lowest point in house take off saddle wire brush hole and surrounding pipe 1/2" flux the pipe heat it and set in solder just manipulate the heat to get it filled Or just get a 1/4 " cap from an A/C supply store
4. better yet get a rubber inline splice connector and simply put in its place and tighten down the clamps
5. Check out this link, it show about how far the ferrule should be on the pipe. If it to close to the end of the pipe you will probably never get it to quit leaking. You may also have a defective ferrule or fitting. http://www.sealexcel.com/single-ferrule-compression-tube-fittings1.html Hope it helps.