Stainless NPT fittings - How to stop leaks?

This is a little off topic, but brewing related.

I recently upgraded my reverse osmosis system with a 14 gallon tank. This will have enough water in the system for a typical brew day. Since the tank was stainless I choose to use stainless fittings and valves. I've used them on my brew rig with no problems in the past. I suspect that since my RO system is at a much higher pressure my mediocre plumbing skills are not up to the task.

I cannot for the life of me get them to stop leaking. with all the fittings there are 6 connections. Some worked, but some of them have very slow drips.

I started out with white "Teflon" tape. When that didn't work I did some research and found out how many types of TPFE tapes there are. I settled on the The Blue Monster mostly because it was available locally. That didn't do the trick. So then I went back to the store and picked up this TPFE paste from the same company. It is supposed to work to 3000 psi and be put under pressure immediately.

I drained the system and gave it another go. I had some very slow leaks when I went to bed last night (one drip every couple minutes). I put a bucked under it and went to bed. By morning they were dripping constantly and had leaked at least 3 gallons to the top of the bucket.

Can anyone help me understand the tricks here?

My thoughts:
- I'm not tightening enough
- I'm tightening too much
- I still don't have the right product for sealing
- Buying my fittings from all over the internet leads to poor quality threads
- Should I scrap all of them and use brass or plastic?

 

How many wraps of teflon tape did you use?

How much I use depends on the fineness or coarseness of the threads. Even with the finest threads, I'll probably have two or three wraps. When I'm threading the fittings together, if I don't have resistance from the teflon tape about halfway on, I probably don't have enough tape.

My initial guess is not enough tape.

 

I played with that a few different ways. With the white stuff I had several. With the blue tape I had 3 or 4. It seems like if I go much more than that it bunches up as I screw it on. Maybe a little bunching is ok as long as most of it stays in?

 

So my racing teammate was the "fluid and air transfer systems engineer" or some such nonsense for Navistar for years. This issue came up when we were tightening male 3/8" NPT to 1/2" flare fittings into oil coolers for the racecar.

Me "So how do you know when you have an NPT fitting tight in a production environment."
Him "The official torque spec is hand tight plus one turn, test for leaks, tighten more if it leaks."
Me "Nice one...you almost got me there"
Him "Its true which with my OE manufactures no longer use them unless no other option presents itself."

Moral of the story is, if you are screwing NPT to NPT and using sufficient tape or sealant that the surface of every thread shows coverage when unscrewed and you still have leaks, you are not tightening enough. Alternatively, the threads were not tapped correctly in the first place.

 

I have had to use 10 or more layers of telfon tape to get stainless pipes and fittings to seal... different manufacturers cut threads slightly different enough it seems to somethimes need to do this... and you always wrap it in a gradual way so it gets thicker as you thread it on and the so the process of threading it on goes with the "grain" so to speak so you arent threading into the top end edge of the tape but rather with it. ..Hopefully that makes sense since I dont know how to explain it any better...

 

I know what you mean augiedoggy. It looks like I was not being ambitious enough with the tape. Fortunately the valve on the tank is holding, so I can shut it down and give it another try without draining the while thing.

Thanks for the help everyone. I think I'll leave some of the paste in the threads, wrap it in a generous amount of that blue tape and hope it works this time!

 

A friend recommended the yellow tape made for gas lines one time. One wrap of that stuff will generally work wonders, it is thicker than the blue stuff.

 

Finally got around to redoing these joints. Interestingly enough all of a sudden the paste gave out at one of the joints and I had a bit of a mess this morning. Nothing like necessity to bite procrastination in the ass.

Using a LOT more of the blue tape got it fixed up on the first try. For some reason the first time around I thought that using just enough was the best thing to do. After doing several layers I could tell right away as I screwed the joints together that they were much smoother and tighter than they were with just a couple wraps.

Now I know!

 

Well what kind of fittings are you using? It sounds like you're using compression fittings. I know a lot of people have problems getting them to seal, and that's because you should never use pipe dope or teflon tape with them. I always recommend this guide to installing compression fittings, it helped me a lot when I first started to dabble with them.

 

This is an old thread. That post last January was the resolution of it. The fittings have not leaked since.

The fittings were NTP fittings. I do know what a compression fitting is and how it is supposed to work.

 

A few of these old "fitting" threads have been bumped up here lately.......I reckon the newbie knows fittings, but not where the date is located.......

Welcome!

 

I'm going to add my 2 cents as long as this was bumped.

Make sure your wrapping the tape around the threads the right way, if you don't they will bunch up as described above. Looking down on the firing wrap clockwise and the screwing action will tighten the tape as you put them together