How tight do you need to tighten a compression fitting?

Hello,

I just hooked up my toilet. It is a Brasscraft valve and I used a solid pipe to connect the toilet. I haven't done this before. I seated the solid pipe into the the valve with the ferrel until it stopped and hand tighetened. I tightened it more with a wrench until it was tight....I didn't over tighten it by putting a lot of pressure. I snugged it up good. I turned the water on and had a very slow leak. I left the water on and did many series of a little turns until the slow leak stopped. I am guessing that I turned the nut about two times until the water FINALLY stopped leaking.....I was concerned I was going to strip the threads, but didn't.

IS THIS NORMAL??...to have to tighten this much?? The guy at Home Depot said I will have to put some force on it as I am deforming the ferrel...and yes, I do think this Home Depot guy knows what he is talking about as opposed to others LOL!!! I just want another opinion.

Thanks,
Doug

You keep going until it seals. Hopefully, you did not use any tape on the threads, as that can cause it to leak, regardless. Sometimes, I'll put a small drop of oil on the threads before assembling the thing and this makes tightening it up a little smoother, but isn't necessary. It's a metal to metal seal...it takes some pressure to make it happen.

Thanks Jim. That's exactly what I did. No tape and little turns until it stopped. I was just getting to the point of, "Holy $&!%.....when is this going to stop leaking!!". It seriously took about 10 times of little turns before it stopped.

IF the tube is NOT straight into the connection, it will take a lot more force to stop it from leaking. WE do NOT know what 10 times of little turns means relative to complete rotations so cannot tell if you tightened it too much, too little, or just right, sort of like Goldilocks and the three bears.

ANother key is not to let the valve rotate or slip any as you are tightening the compression nut. Have a good grip on the valve with your backup wrench.

I think they were referring to the riser compression joint, not the one on the supply pipe..

As i read it, the OP turned the nut at least 2.5 times after snug. IMHO, this is way too much and I would have started over with a new ferrel, and potentially new riser if it was crushed. Most compression fittings out there come with literature telling you how far to turn after snug. I have never seen one saying you should turn it that much. Usually its like 3/4 turn past snug. Any more than that, then you have a problem.

As I read it, OP posted over 4 years ago, and yesterday somebody created an account to promote his site.

This is not to say that actual discussion about how much to tighten a 3/8 compression fitting on copper is not worthwhile.

A lot depends on the friction of the fittings. I don't bother counting how many turns, because each one is different.

BazMan25 said:

Doug
Really you should only tighten a compression fitting about 1.25 turns, but I like to do turns in small increments and check for leaks after each turn. You can always tighten a compression fitting more, but you can't un-tighten a compression fitting. Here's an article that tells you how to tighten a tube fitting and what can happen when a tube fitting is over tightened.

Click to expand...

I agree. I used to build pneumatic panels and 1 1/4 turn was standard. Never had leaks and many of the valves/lines were test at 150 PSI.