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I installed a new dryer last week and, in doing so, purchases a new flex pipe as they say you should never re-use the old one.

I now need to make some adjustments to the flooring so need to pull the dryer out fully and to do that, I need to disconnect the flex pipe.

Can I disconnect then reconnect when done?

I assume I can, but you are nearly always told to always use a new flex pipe every time you're doing a new install. I assume that's to just not use a decade-old pipe rather than the fact that they can't be reused at all.

(These seems like a dumb question now that I read it outloud...)

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It's not a dumb question as a number of metal seals are one time use only. I'm curious if someone has an answer. –  diceless Aug 25 at 20:17
    
Well you can check for a leak on your own pretty easily. I have to admit I have never given this much thought - and I have disconnected my dryer hose at least 10 times the past 5 years. –  DMoore Aug 25 at 20:22
    
I decided to check BrassCraft (common manufacture of lines here). They have this on their site. "Q: Can a gas connector or gas fitting be re-installed? A: No, the product standards and model plumbing codes prohibit it. Products may be damaged during removal or re-installation and may be unsafe for use." –  diceless Aug 25 at 20:27
    
Does anyone have the code in question they are referring to? –  diceless Aug 25 at 20:28
    
@diceless yes, that's the somewhat vague wording I'm hung up on. Is there a difference between 'reusing old flex pipe to connect a new appliance' vs. 'disconnect and reconnect a new flex pipe to make adjustments to appliance location'? –  DA01 Aug 25 at 20:31

1 Answer 1

up vote 4 down vote accepted

International Fuel Gas code prohibits the reuse of any Pipe, fittings, valves, or other materials.

International Fuel Gas Code 2012

Chapter 4 Gas Piping Installations

Section 403 Piping Materials

403.2 Used materials. Pipe, fittings, valves and other materials shall not be used again except where they are free of foreign materials and have been ascertained to be adequate for the service intended.

It also specifies not to reuse them in the installation instructions.

DO NOT reuse connectors, fittings and valves; they are designed for use on original installation only. Removal of connector and additional handling may damage connector making it unsafe for reuse.

Overall this is to help prevent leaks caused by dirt, debris, and damage that may prevent good connections. In this specific case, it's because the threads on the fittings involved are actually mashed together when the connection is made. This type of connection does not require pipe dope (which it also mentions in the installation instructions), since the seal is created when the threads get squished together. See the National Pipe Thread Fuel (NPTF) section of this answer for more detail.

Usually when replacing these type of fittings ("hoses"), you'll have to replace right back to the black pipe. If you have a valve with a flare end that the fitting ("hose") connects to, you'll want to replace the valve and fitting ("hose"). If there's an adapter with the flare, you'll replace the adapter and fitting ("hose"). Make sure you clean the threads of the black pipe really well, to insure there's no foreign material in the threads, before you connect the new fittings. You might also have to replace the flare fitting on the dryer as well.

The other problem with these fittings; though usually only fittings that have been in use for some time, is that they can actually be damaged when they are removed. Sometimes the threaded nut doesn't spin, and the pipe actually ends up twisting. This can cause damage to the pipe, and so it should not be reused in this case.

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The last paragraph makes a lot of sense...old ones shoudld always be replaced. I just feel bad having to replace one that is only 3 days old. So, in general, it is fair to say that whenever an appliance person disconnects a gas appliance to service it, they always put on a new flex hose? I better plan ahead so I'm only disconnecting this once. This could get expensive. :) –  DA01 Aug 25 at 22:34
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> ...except where they are free of foreign materials and have been ascertained to be adequate for the service intended... –  TDHofstetter Aug 25 at 22:45
    
@TDHofstetter this is why you can reuse most black pipe fittings, and don't have to replace all the plumbing in the building every time you make a change. However, in this case the threads of the fittings will be deformed, and not adequate for the service intended. The manufacturers installation instructions even say specifically not to reuse the fitting. –  Tester101 Aug 25 at 23:19
    
So now I need to post a question about craft ideas for re-using decommissioned flex pipes. –  DA01 Aug 26 at 3:45
    
The threads do not become deformed any more than any other thread when screwed together. The flared end of the tube gets squished to mate with the flare fitting, it's a metal-to-metal seal. The gas code does not prohibit reuse other than there is probably a "General Clause" to follow all manufacturer's instructions. The manufacturer states not to reuse because the assumption is the layperson may not conduct thorough check to ensure it is "adequate for service" and also may not know how to properly check for leaks. –  Jimmy Fix-it Aug 26 at 12:25

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