Talk:Trap (plumbing)

Name
I am from the UK and until today I have never heard the term "trap" (though I am not a plumber). I have only heard them called "U-bends". Maybe this is UK terminology? Googling for "U-bend" returns only UK sites for the first 20 hits. I have changed the article to mention the term "U-bend". PGibbons (talk) 14:50, 15 December 2007 (UTC)

Yes this is the UK's terminology for the trap I have added S-bend as well due to it being the original and still a commonly used term. —Preceding unsigned comment added by 217.20.20.70 (talk) 11:08, 17 June 2009 (UTC)

The article is terribly US-centred. I've changed a few things to make it clearer info is in relation to the US only. A U bend is nothing like a 'P' !

Where?
Under the heading "== Accepted traps ==" the sentence starts with: "In many locations, "S" traps are no longer accepted...". Since wikipedia-articles are read all over the world the designation "many locations" is rather insufficient. --VanBurenen (talk) 12:04, 17 June 2009 (UTC)

Heading changed to refer to US only - improves this issue and the accuracy of the article.

horizontal length
How long should the horizontal be before going down to qualify as a P trap instead of an S trap? I saw a video converting a P trap into an S trap with only about 6" of horizontal. Seems like as long as the pipe flattens enough to let air back to break the vacuum it will work. — Preceding unsigned comment added by 65.95.64.182 (talk) 22:21, 11 June 2014 (UTC)

To avoid siphoning the P trap dry, the horizontal needs to have a vent in it whose inlet is downstream from the P trap and above the level of the standing water in the P trap. If the horizontal is un-vented, the P trap becomes, effectively, an S trap.

The P-trap built into toilets is an exception to this since that trap is filled from the toilet tank. — Preceding unsigned comment added by 216.223.234.127 (talk) 16:13, 7 March 2020 (UTC)

Correctly designed U bends will not siphon dry. The up leg of the trap should be long enough to retain sufficient liquid to ensure the U is correctly filled after flow has stopped. — Preceding unsigned comment added by 80.225.1.119 (talk) 14:01, 16 July 2020 (UTC)

trap in zero gravity
trap in zero gravity enviroment will not work. — Preceding unsigned comment added by 85.193.250.22 (talk) 00:16, 2 April 2015 (UTC)

What about drum traps??
Other than a mention that drum traps are generally discouraged or banned ... there's nothing here or elsewhere about drum traps. They're commonly used with bathtubs ... and even if not part of current codes is still widely installed in existing housing. LibraryGeek (talk) 19:59, 13 May 2019 (UTC)

S vs U traps?
It's unclear to me, what difference between the S-Bend and U-Bend is. In several places (both on this page, and in the page for Thomas Crapper), the text reads "The S-Bend [was invented by...] but became known as the U-bend following the introduction of the U-shaped trap". So what exactly was "introduced" to distinguish U from S? Is the sideways-S-shape merely more elongated? If somebody familiar with the references could clarify the article, it'd be helpful. not-just-yeti (talk) 15:30, 10 January 2020 (UTC)

'S' is equivalent of a un trap on its side. Physically, the 2 are the same, the S being more compact and giving a general linear piece of pipework, usually in the directly down direction. See picture of same on the page. — Preceding unsigned comment added by 80.225.1.119 (talk) 14:04, 16 July 2020 (UTC)

It may be that the "U" trap is is so called because the U shaped descending section is attached using unions so it can be dissasembled in-situ for cleaning, while earlier S-traps were a single-piece casting and could not be disassembled 2406:E000:6B8B:5D01:7964:23B:58F2:D5CD (talk) 01:31, 31 December 2020 (UTC)

Original Author has limited experience
Firstly, clearly American with drainage knowledge only. I've modified sections to state 'US' as clearly that's what it's about. Reference to 'codes' is a US thing. Other countries may have 'regulations' or other terminology for maintaining standards.

I've added 2 further uses - in heating systems to stop thermo-siphoning and heat loss (e.g. into lofts) and in the use of pressure gauges - notably steam pressure where bent pipework immediately before the gauge offers an air barrier to the steam.