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Question DetailsAsked on 3/4/2018

How much would it cost to have a plumber cap a gas line that was going to a gas dryer?

We used to have a gas dryer but no longer use it and we would like to unhook it and have the gas line that was leading to it capped off so it’s safe and no gas will leak out once it’s unhooked.

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Generally, unless you are worried about the gas valve leaking through the stem (usually only after many decades, and then generally only a very minor leak, just enough to smell a touch), usually just shutting off the gas valve that is there and removing the flex tubing, then putting a flare cap on it does the job to protect the open end of the valve from corrosion or impact damage and also to stop any outflow in the event the valve valve itself leaks a bit internally over time.

Use gas-service teflon pipe tape wrapped 2 turns clockwise (looking from the open end of the gas valve towards the handle) on the threads (usually gas service tape is a yellow teflon like tape, about $2 for a small roll - NOT the usual white plumbing teflon tape for water pipes) and snugly - and then NOT reefing on it, just snug - put on a flare cap of right size. Normally the male end of the gas valve (the end the flex tubing connects to and where you would be putting the cap) is 3/8" flare size - NOT regular 3/8" NPT pipe like black iron. Normally $1-3 each - here is a sample in 3/8" - note the 3/8" or 1/2" for 3/8 or 1/2" pipe is the approximate inside diameter of the opening, NOT the outside thread diameter.

Assuming the gas shutoff valve totally shuts off (meaning you cannot smell gas coming out of it when shut off and tubing removed, though or course there will be a spurt of gas smell when the tubing is removed and the bit of gas in it dissipates into the air, and also if you put your nose up right to the valve you WILL smell gas for months), remove and take the flex tubing with you to the store (Lowes and Home Depot among others carry these caps) to double check with a 3/8" flare plug or nipple (possibly 1/2" if large capacity dryer or older one) in the flex tubing for thread size match - then get same pipe size flare brass (has to be brass) CAP to go over the end of the gas valve. This assumes your gas valve is the standard male end sticking out - obvisouly if female thread on the valve end, you need a brass PLUG rather than a cap.

If the gas pipe is in the way of the new electric dryer, you can't or don't want to try capping the valve itself, or you just don't trust the gas valve stem to be gastight forever, minimum Plumber service charge ($75-350 depending on area, usually around $90-150) should apply for this about 5-15 minute job, plus maybe $5 parts, remove the gas valve, remove the nipple or cut the pipe back as needed for clearance, and cap the gas line itself. Handyman probably about half that if you have one you trust playing with gas piping - because if the valve has to be removed or the gas line cut back the gas supply will probably have to be shut off outside, then turned back on and all gas appliance pilots relit and appliances tested for proper function. To just replace the valve with a cap on the pipe, or to remove a nipple leading to the vavle and put in a cap or plug without any pipe cutting needed, most plumbers would do that without turning the gas off - just remove the valve or nipple and stick their thumb over the open pipe end while they tape wrap the thread, then put the new plug or cap on. (Gas pressure is only a fraction of a psi, so not much gas escapes doeing that.)

Note if you cap the gas line, as opposed to just capping the valve, come resale time the buyer may insist the gas valve be put back on ready to hook up a gas dryer. Your call - if this is your "forever" house you may choose to cap it (and the range one capped too if changing that to electric also) - I did so at our current "forever" house when we put in electric range and dryer, just for peace of mind, because a leaking valve stem back there could conceivably build up to explosive gas levels under/behind the appliance without noticing the smell and ignite when the appliance (or adjacent washer) is turned on.

Question of whether you are as paranoid about natural gas safety as I am - though I admit, even though in high seismic risk area, I was not so paranoid as to cut that branch gasline where it came off the main feed into the house near the furnace and water heater. Personally, if electric weren't about 3 times the cost of gas heating in our area, I would have gone with an all-electric home for peace of mind, but that comes from seeing a few nasty gas leak accidents and gas leaks after major earthquakes and tornados and such burning houses down or blowing them up. All goes back to your personal experience.

Answered 2 years ago by LCD

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