Impossible-to-seal plug

[Fnord]

Alright, this is driving me nuts.

-I have a 2" steel plug.
-I'm trying to get it to seal in a 2" steel coupler
-They won't seal no matter what I do.

So far I've tried:

PTFE tape
Pipe dope
Electrical tape
Plastic bags
Roofing sealant
Combinations of sealant/dope with tape

Nothing works.
I'd prefer to be able to take them apart afterwards, so I can't solder/jbweld them.

Any ideas?

[/list]

[DYI]

If none of that will seal it, there may be a defect in the threads somewhere. Either that, or you didn't use enough PTFE tape. If you're using the white stuff, I use about 10 feet of it for a 2" joint.

[Fnord]

I used roughly ten feet... But that was the last of what I have right now, so if it needed more I can't do anything until I get another bulk load.
And I checked, the threads are perfect, but the coupler has threads that are cut straight, not ones that make the opening narrower as they go in (can't think of the word). That might be a problem.

Thanks though.

[POLAND_SPUD]

so your plug has tapered threads (I think this is the correct word, but don't take taht as 100% sure I am non-native speaker )

hmmm so try to find a plug that has the same threads as your coupler...

[mark.f]

Get a coupler with tapered threads. Straight threads and tapered threads are not very compatible.

If you must, concentrate the teflon tape towards the top, (widest), part of the plug.

[MrCrowley]

You could always JB it, when you need to take it apart just get a chisel and a hammer, it comes of fairly easy.

Also when applying pipe dope I find it work better if you leave it to dry, even though it didn't say that on the dope I had.

[Killjoy]

You could try some silicon sealent, but concentrate the majority at the top...as mark suggested with the tape.

You could also try wraping the fitting or doping it quite a bit, screwing it on, and then smearing a good amount of 5 minute epoxy at the joint. That should seal it and the epoxy will break off real easy if you unthread the plug.