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afaroo · Sep 17, 2009, 12:41 AM

Hello Milo,

I would like to know what is the purpose of this dirt arm and why it is needed, Thanks.

John

speedball1 · Sep 17, 2009, 03:26 AM

I would like to know what is the purpose of this dirt arm and why it is needed,

Good morning John,
I too wondered what a "dirt arm" was and what relationship dirt had with drainage.
This has just got to be a West Coast expression because I've never heard it used any where else.
In my area we call the horizonral pipe in the wall that runs from the stubout to the sanitary tee in the vent a "lateral drain".
Perhaps Milo can chime in and give us the history of the term and why it concerns dirt.
My personal guess would be that it was shortened down from "dirty arm" but I don't know why it would be "dirtier" then any other drainage pipe. Lee, you're out on The West Coast. Do you know? Come on Milo! Inquiring minds want to know. Tom

Come on Milo,
We're waiting.

mygirlsdad77 · Sep 17, 2009, 05:53 PM

Im actually in the Pacific Northwest. (Montana to be exact). Tom, the phrase I have heard is dirty arm(as you were thinking). Its been awhile since I heard the phrase,(think it was in one of my training books when I was an apprentice.) Don't think its in the UPC book. I always thought it was what I call a trap arm. Basically, a horizontal drain between fixture trap and trap vent. Im sure Milo will give a much better description of what he calls a dirt arm. No dirt involved, just a name that someone thought up a long time ago, and stuck with some of us.

P.S. Now that we all know I'm from Montana,

1. I don't have one of those crazy cowboy accents.

2. I do have electricity(hence the internet), and its not gas generator powered.

3. My sky actually is mighty big.

4. I do know plumbing(or at least as much as I've had the priveledge to learn and see first hand, and the awesome knowledge I gain from this site, and common sense.

5. And most importantly. YES, we finally have running water in Montana, otherwise, I would be searching Monster.com right now looking for a job. Either that or making love to sheep. Oh thank god we have modern plumbing in Montana these days.

ballengerb1 · Sep 17, 2009, 06:08 PM

Although I have heard that term used by a few plumbers in my area it does not show in any plumbing glossary I can find. Then again they also no longer have stop cock either

KISS · Sep 17, 2009, 06:26 PM

Well heard of dirt legs, but not arms. Need to learn something new anyway.

Widdershins · Sep 17, 2009, 06:30 PM

Originally Posted by afaroo

Hello Milo,

I would like to know what is the purpose of this dirt arm and why it is needed, Thanks.

John

A "dirt arm" is as MGD stated earlier; It is the trap arm, which is the horizontal branch between the vent and the trap.

The origin of the term is based more or less on the fact that the stretch of pipe between the trap and the vent (the trap arm) is where the "dirt" (waste) is introduced into the drainage system.

It is an archaic term, one I haven't heard used in over 10 years.

mygirlsdad77 · Sep 17, 2009, 06:32 PM

I still call angle valves under sinks and toilets stops, and gas shut off vavles cocks. But you are correct, you don't see these terms in the code books any more. Maybe there's a reason for this. The language in old school plumbing would be found affensive these days.

Stop cocks, nipples, rector seal(or as I like to call it, rectum seal), male adapter into female adapter, ball cocks so on so forth.lol.

ballengerb1 · Sep 17, 2009, 06:35 PM

You should have seen the look on the lady clerks face at Menards when I asked where she kept her stop cocks. Priceless

mygirlsdad77 · Sep 17, 2009, 06:50 PM

Wish I could have seen that. Priceless indeed.

speedball1 · Sep 18, 2009, 04:54 AM

You should have seen the look on the lady clerks face at Menards when I asked where she kept her stop cocks. Priceless

Thanks for the first chuckle of the day Bob. Are you certain you didn't follow it up with,
"And where do you keep your nipples?" Very funny! Tom

speedball1 · Sep 18, 2009, 05:00 AM

I would be searching Monster.com right now looking for a job. Either that or making love to sheep.

I've heard some weird stories about you cowboys and sheep. Or was it " Bareback Mountain" I was thinking of. LOL! Cheers, Tom

cyberheater · Sep 18, 2009, 06:28 AM

My grandfather used that term. I would get the job of having to ensure he would not loose anymore fingers while he was working on his projects. Also, he could get a little langauge happy. He used that (and others) for other things too. Not going to directly write that, for a good reason. (grin)

It is exactly what mygirlsdad said it was in plumbing terms.

Milo Dolezal · Sep 18, 2009, 08:14 AM

I am little late to this conversation: Dirt Arm is a very important part of rough-in installation and is used here (so.Cal.) on everyday bases. As correctly explained be ImGrowler, it is an unvented horizontal extension between trap and vertical drain. There are certain limitations as to how long this pipe can be depending on size of pipe.

For example: Dirt Arm is used in situations like kitchen where you have large window with sink under it. As per Code, and from Structural reasons, you cannot drill King Stud and Trim Stud ( 2 studs that are on each side of window ). So you run your vertical drain/vent on one side of window, bring out dirt arm inlet under 45 degrees (San T) and let drywall to be installed. After cabinets are in, you drill through cabinets and wall mount dirtarm between San T and sink cabinet. Therefore, this pipe is visible inside the cabinet. This is DirtArm.

As far as the terminology goes: sorry, I do not know where this term originated from but I assume it is called "dirtarm" because it is a long piece of unvented pipe which is constantly clogged up with (kitchen) waste.

speedball1 · Sep 18, 2009, 03:47 PM

M ilo,
We all know what it means. We simply wanted to know where it came from. I still like "dirty arm". Tom

afaroo · Sep 18, 2009, 07:51 PM

Thanks to all learning something new every day.

Best Regards,
John