We're nearing the end of a kitchen remodel, and my contractor ran a new "flex" line from our existing black 3/4" gas pipe to connect to a new cooktop. From googling and reading, I already know that gas pipe sizing can get complicated depending on the other gas appliances being used and the way the the pipes are run. So for now, I'm going to ask what I hope is a more simplified question that may still tell me what I need to know..

I read that corrugated flex pipe can greatly reduce the CFM/BTU capacity depending on length and number of bends.

So Ignoring other variables that could actually reduce the max capacity of this new line only (and could change this answer from a yes to a no).
Can a 1/2" (ID) flex pipe that is 25 feet long, and then has an additional 3 hard-pipe elbows before it gets to the cooktop, even be able to handle the 55,000 BTU requirements required by the cooktop at all, even under favorable conditions?

A CFM calculator I attempted to use suggests that it cannot, and that we'd instead need a 3/4" ID pipe to handle that capacity under any circumstances (but I'm no expert, so why I'm asking here).

Sorry I don't know anything about my gas pressure, but I can say this is a residential single family house that is 40 years old. The initial gas comes in from the meter on 3/4" black pipe.

Thanks in advance for any info..
-Gary.

using the lowest of these charts, you are getting close to 60,000 btu at the stove.
other of these charts have you way over 100,000 btu.

so, given that a stove top burner is about 7,000 btu and the oven is about 16,000 that would give you a max of 44,000 with everything running full tilt. (you can't use the oven and the broiler at the same time)

I'm going out on a limb and say you have plenty..

[www.gastite.com]

I'm sorry, but you can't ignore everything else that might make it not work. All the information is needed to determine if a pipe size is appropriate. The 3/4" you tapped off may be barely adequate, by itself, for any appliances it supplies. We'd need more info.

He said "cooktop" not "stove". You would have to use the data for THAT brand of CSST pipe, because they are NOT all the same size, and the flow characteristics are not the same as for steel pipe.

Tracpipe counterstrike (the best csst on the market) chart says you should get 63k @ 25 feet.I my eyes these charts are very cautious and you can always squeeze a little more out of them.Besides if you have an issue you can always call the local Plumbing inspector.

You would really open a can of worms if you did that after installing the gas line without a permit or inspection.

Paul48, my intent was not to ignore everything else. My thought was that if even ignoring everything else, 25 feet of 1/2" ID pipe was not enough even if nothing else is consuming gas, then it certainly would Not be enough when you Do include all the other appliances.

Thx!

Since there actually are 2 gas furnaces in the house, a gas water heater, and 2 fireplaces with gas starters.. even if the 25ft 1/2" flex pipe could handle it in an isolated environment, it sounds too close for comfort to assume this will be enough given the other appliances in the house.

Let me know what additional info I should give and I'll do my best to provide it.. be easy on me with all the terminology though, as mentioned I'm not an expert. I'm just trying to make sure the contractor is not screwing it up or trying to pull something over on me..

Thx.



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Sizing of the gas piping can be done with a diagram like this and each section between appliances and the appliance branches can be determined.

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You need to know the pressure coming into the house. With that amount of large volume appliances you may have 2lb coming into the home. That is a completely different chart than one for half-pound. It requires regulators for each appliance. If you have what looks like a small space ship in the piping at each appliance, that would be a good indication you have higher than .5 lb.

"Since there actually are 2 gas furnaces in the house, a gas water heater, and 2 fireplaces with gas starters.. "

with all this, let alone the gas stove, I would say your main is severely undersized.

I think I'm going to get an inspector to check it out for me..
Thanks for everyone's input!



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The diagram shown in this message set should show the pipe sizes for better understanding.



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