Need to Change Plug on Propane Tank

[3x5]

Need to Change Plug on Propane Tank


I have a 2004 Manchester propane tank, 42.7 gallons, on my 2005 Alpine Coach. I can't figure out what the model number is, but I am including a picture of the id plate. There is a pipe plug just to the right of the fill plug that has a tiny propane leak that I found with soapy water. Here are a couple of pictures of the plug too.


I want to replace the plug myself, which seems extremely simple. But internet searches are giving me more questions than answers. But I bet this is easy stuff for most of you guys.


For others doing this, I want to say that an ordinary six point ratchet socket will not fit on the plug. It has a square head. A 5/8ths inch open end wrench fits fine, but you can't get enough leverage to turn it. What you need is a 5/8ths inch female "pipe plug socket." They are not easy to find, but I did find a small set on Amazon.


I tried tightening it slightly per the advice of a mechanic. It did move slightly, but after tightening it as much as I dared, it still leaks. The tank is half full, so I will have wait for it to empty before I can take the plug out.

I called Manchester tanks for the correct part. They gave me part number F30235, and said it is a 3/4 inch NPT plug, but can't give me any more specifications. They can't sell them directly to consumers. They couldn't tell me who manufactures the plug for them. Of course, they couldn't tell me if I could just buy a 3/4 inch NPT plug over the counter at Home Depot or anywhere else. They say I have to go to an "an installing RV dealer" to order one from them, or a distributor. Turn around time is over a week. Price will up to whoever I order though.


So, will any metal over the counter 3/4 inch NPT plug work? Would galvanized be enough, or maybe brass to play it safe?


Should I seal NPT tapered threads? I am guessing yes. What should I use? I think dope is supposed to be better than tape. I hear that you are supposed to use a dope made for propane, and that one for natural gas is not good? I could use a recommendation of something I could find at a local hardware store.


NPT means that it is tapered, which I think means I have to be extra careful not to tighten it too much. I could fake it, but I would like a torque number. But I don't think torque works with tapered thread. So is there a formula, like finger tight plus 2 to 3 turns?


Thanks for your help!

[SteveJ.]

First off, go ahead and either burn off the propane through the furnace and cooktop or just vent it to atmosphere in a spark free area.

Do not use galvanized fittings with propane. Black pipe or brass are good. I would first try cleaning up the old fitting, re-dope it and give it a go.

[3x5]

Yeah, if it takes too long I will just vent it out in the desert. But 20 gallons x $3.50 is $70.

I would rather just get a new fitting than risk having to do it again.

Ok. Black pipe or brass. No galvanized. My big question is would just buying a nice brass 3/4 inch NPT pipe plug at Home Depot work? I am guessing it would.

[Alpine36]

Buy a good quality brass npt pipe plug at the hardware store, clean the threads in the tank well and use liquid thread sealant such as this Loctite.
Avoid using Teflon tape. Maybe it’s just me, but I’ve had mediocre success with Teflon tape and LP pipe fittings.
https://www.amazon.com/Loctite-442-5...00O05CS6&psc=1

[TandW]

Do NOT use cast fittings for gas service. Only forged.

[3x5]

I found a plug that looks just right at a plumbing supply store.



Thanks to everyone for their advice.

[wolfe10]

What pipe dope do you have/ will be using?

[3x5]

Master Plumber brand 540377 Yellow Formula 55 Thread Seal. I found it at True Value. It specifically includes pipes carrying propane on the label.

Manchester Tanks told me that I need to get a thread seal that is specifically for propane and not just natural gas. That sounds a little odd to me, but I am playing it safe.

[Old-Biscuit]

Not sure what Manchester is talking about. Natural Gas vs LP

Master Plumber brand 540377 Yellow Formula 55 Thread Seal is for LP, Natural Gas and Oxygen.