Author Topic: Underground Pipe and tubing size  (Read 245 times)

Offline Steve.Keelan

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Underground Pipe and tubing size
« on: June 17, 2020, 03:21:56 PM »
So I was out to a client's place to quote on a new unrelated heat pump system at this time I also disconnected and capped 2 80k btu furnaces,  (1500 sq ft farm house) when I eventually was able to locate secondary reg to shut off supply downstream I noticed the copper supply line from primary reg was noticeably small. For reference the primary reg and torpedo tank are located approx 60' from secondary, the line as it turns out is 3/8" copper tubing, it does not appear to be run in a channel, is buried almost immediately from tank, it goes beneath a gravel driveway and an enclosed deck/sunroom/cut wood dry storage where it comes back above ground and is supported to the exterior wall of home. After a bit of code review and referencing I flagged it as undersized. Being that both propane appliances had been disconnected and the line capped and that they are friends, I did not tag it at that time but did advise that to install another line to supply an outdoor range the line would require replacing as its currently under sized. I advised itd be a fair bit more expensive for me to perform the work as itd involve renting a mini exc scheduling locates etc where if they had the company whom installed the line (15 years ago) but is still also their propane provider,  come out and make their line compliant then it'd be significantly cheaper for my client. I referenced clause 6.15, 6.15.1 from b149.1-15 and clause 5.9 from b149.2-15.

A guy from the supply company comes out and tells my client "city folk dont know propane, thats for natural gas propanes higher pressure" then he leaves his card and a note saying 2ndry regs rated for 2mil btu, 3/8 copper is good for 450kbtu, and the last line on note in bold underlined was propane vs nat gas code??? I get this from client and think maybe theres something im missing but immediately am skeptical of this guys proclamation of city folk dont know propane and higher pressure, to me logically and scientically higher pressure requires larger pipe not higher pressure validates use of smaller pipe and his indication of 450k btuh on 3/8" copper. I check the tables for 1" pressure drop on 11"wc and read that max btu for 3/8 copper is 23k btu. Am I missing something here or am I correct in my original findings?

Tldr  propane Supply (11w.c. 1 drop) 3/8" copper tubing ran underground 60', I flagged as undersized. 6.15.1 Piping having a nominal pipe size of less than NPS 1/2" shall not be used. B149.2-15,  5.9 - Piping shall comply with clause 6 of csa b149.1

Kelly propane says 3/8 copper good for 450kbtu city folk dont know propane.

Is there something im missing or am I correct in saying minimum pipe/tube size.for burial is 1/2" and they should fix their own deficiency?

Offline Hgye

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Re: Underground Pipe and tubing size
« Reply #1 on: June 20, 2020, 07:30:12 AM »
You are wrong. He is right.  3/8” copper at 10 psi and 60’ is good for 448,000 btu.

Copper is TUBING not PIPING.

Offline Porcupinepuffer

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Re: Underground Pipe and tubing size
« Reply #2 on: June 27, 2020, 10:06:31 AM »
to me logically and scientically higher pressure requires larger pipe not higher pressure validates use of smaller pipe

Nope. Think about it. On propane, we're barely trickling 11" w.c. through residential tubing/piping. When we open it right up, the tiny flow rate can only let so much escape a small pipe that we can easily block it with our finger. We're talking less than a quarter of one PSI.
Now take that same pipe and have it pushing 10psi instead of 11" w.c. and you'll have a hell of a lot more flow coming out. So since that same size pipe at the higher pressure can obviously deliver more because of the excessively higher velocity that can flow through it, it will have a lot more it can supply.

Just look at all the older natural gas meters with the copper. They're fed with a high pressure 1/2" line before the reg. It easily supplies the btus required for the 1" and larger black iron after the regulator.

...And anything smaller than 1/2" pipe cannot be buried. Not tubing. Make sure to pay attention to those differences with piping/tubing. It's easy to get them mixed up.