I have a leak in a Grohe bathroom faucet. It has a 3/8" compression fitting. I've tried thghtening it, adding an 'O' ring, used teflon tape and pipe thread compound.. it still leaks. Any suggestions?

Which faucet do you have and where exactly is the leak? Grohe Faucet Parts (http://www.chicagofaucetshoppe.com/Grohe_Faucet_Parts_s/752.htm) No O rings or tape on a compression fitting. Was there a brass ring under the nut?

The faucet is a Tenso model. The leak is where the flexible line from the faucet connects to a brass fitting at the end of a rigid crome supply line. There is no brass ring under the nut.

The faucet is a Tenso model. The leak is where the flexible line from the faucet connects to a brass fitting at the end of a rigid crome supply line. There is no brass ring under the nut.

Show us a picture please.

The pictures are attached. The leak is coming from between ths chrome nut on the flexible line from the faucet where it connects to the brass fitting.

Berniea96,
Type of the faucet has nothing to do with your leak. It is the actual connection that leaks. If I am not mistaken, Grohe 3/8" compression nut does not use O-ring. It is metal on metal connection. Use 2 crescent wrenches. Hold the fitting tight with one of them while tightening the nut on Grohe supplied connector. Also, I would replace your existing water supply connector ( the solid tube ) with flexible line. These tubes are coated with layer of chrome that cracks under pressure from the fitting causing negative seal. Also, flexible water supplies are much easier to work with and carry less possibility of leak. Let us know how you did. Back to you. Milo

I tried tightening it before the 'O' ring, teflon, etc. it didn't work. When I took the connection apart I didn't see and metal type compression ring.

Then it looks like you are over-tightening... Try again. Tighten by hand then 1 full turn. That should do. Back to you. Milo

Should there be a metal ring in the fitting?

..

The leak is occurring at the top arrow ao the right.

There should be cone-shaped brass looking end inside the threaded end of the supply line...

There isn't. This faucet has been installed for over 5 years and just started leaking. Are there locking ends avail for purchase?

Are there locking ends avail for purchase?
Not sure what you mean by locking ends. If you mean the brass fitting it is called a 3/8" compression coupling.
Strange that it would start leaking after 5 years. If you can't stop the leak by tightening I would change out the coupling.

Remove the braided flexible supply line. Inspect the rubber seal inside the connector. If it does not look defective replace the brass coupling. Unscrew lower nut and replace coupling. You should not have to replace the nut and compression ring on the lower end.

How is that flexible braided line attached to the faucet? Is it made as part of the faucet or is it screwed on a threaded fitting. Show pic if possible.

I think the flexible is made as part of the faucet, but I can't see the connection, there appears to be a plate over it. There was no rubber seal inside the connector at the end of the flexible hose. I'll try replacing the coupling this weekend and let you know if that works. Thanks.

If there is no seal inside the flex connector you will never be able to get a water tight seal. You could try putting an "O" ring in but it is not likely to work.

Chances are that the flexible supply tube is connected to the faucet with a threaded fitting. If so you can replace it with a flexible tubing long enough to reach the stop valve.

If the flexible tube is made onto the faucet body and cannot be replaced and an "O" ring will not seal at the compression coupling you may be able to cut off the ends of both the flexible tubing and the hard tubing then insert the hard tubing inside flexible tubing and use a hose clamp to seal. Don't know if hard tubing will fit inside flexible tubing .

Instead of trying to find an "O" ring;

If there indeed is no seal at the flex tubing nut I would buy a new, short 3/8 flex supply tube, cut off the nut. Cut between nut and crimp so I could remove the rubber seal with out damage. Then try to put the seal on the existing flex tube.

I just happened to have Grohe kitchen faucet in my hands yesterday. Its 3/8" supplies have compression nuts. No washers. See the pic. Do your ends look like these ? Back to you. Milo

It turns outthe leak was from a pin hole in the threads of the brass fitting beterrn the faucet and the chrome tube. Once it was replaced the leak stopped.