# Trap question **URL:** \ **Category:** Plumbing Inspections\ **Created:** [June 26, 2007, 5:05pm UTC](https://forum.nachi.org/t/trap-question/17816 "2007-06-26T17:05:00Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![dmacy](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/dmacy/32/1466_2.png) [@dmacy](https://forum.nachi.org/u/dmacy)\ **Post date:** [June 26, 2007, 5:05pm UTC](https://forum.nachi.org/t/trap-question/17816/1 "2007-06-26T17:05:00Z")
Is the trap needed at the disposal? Shouldnt a straight pipe be used. If there is a issue can someone explain or is this OK. ---
**Author:** ![dvalley](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/dvalley/32/206092_2.png) [@dvalley](https://forum.nachi.org/u/dvalley)\ **Post date:** [June 26, 2007, 5:07pm UTC](https://forum.nachi.org/t/trap-question/17816/2 "2007-06-26T17:07:45Z")
A trap at the disposal is fine. ---
**Author:** ![dmacy](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/dmacy/32/1466_2.png) [@dmacy](https://forum.nachi.org/u/dmacy)\ **Post date:** [June 26, 2007, 5:09pm UTC](https://forum.nachi.org/t/trap-question/17816/3 "2007-06-26T17:09:42Z")
Thanks Dave ---
**Author:** ![bwiley](https://avatars.discourse-cdn.com/v4/letter/b/8c91f0/32.png) [@bwiley](https://forum.nachi.org/u/bwiley)\ **Post date:** [June 26, 2007, 5:14pm UTC](https://forum.nachi.org/t/trap-question/17816/4 "2007-06-26T17:14:21Z")
Except that unless I’m looking at it wrong, you shouldn’t have two traps in succession on the same drain line. ---
**Author:** ![dvalley](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/dvalley/32/206092_2.png) [@dvalley](https://forum.nachi.org/u/dvalley)\ **Post date:** [June 26, 2007, 5:16pm UTC](https://forum.nachi.org/t/trap-question/17816/5 "2007-06-26T17:16:15Z")
David, They could have done it this way also… [http://z.about.com/d/homerenovations/1/0/t/-/-/-/11attachedrain400x300.JPG](http://z.about.com/d/homerenovations/1/0/t/-/-/-/11attachedrain400x300.JPG) ---
**Author:** ![dmacy](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/dmacy/32/1466_2.png) [@dmacy](https://forum.nachi.org/u/dmacy)\ **Post date:** [June 26, 2007, 5:17pm UTC](https://forum.nachi.org/t/trap-question/17816/6 "2007-06-26T17:17:14Z")
> [@bwiley](#): > > Except that unless I’m looking at it wrong, you shouldn’t have two traps in succession on the same drain line. They are on the same line. What would the problem be with the extra trap? ---
**Author:** ![bwiley](https://avatars.discourse-cdn.com/v4/letter/b/8c91f0/32.png) [@bwiley](https://forum.nachi.org/u/bwiley)\ **Post date:** [June 26, 2007, 5:25pm UTC](https://forum.nachi.org/t/trap-question/17816/7 "2007-06-26T17:25:21Z")
In this case, probably nothing because the second sink drain acts as a vent in-between the traps. Two traps in the line though can act as an S-trap, or can cause poor drainage. In any case, it looks amateurish, which should raise red flags! 😉 ---
**Author:** ![jpope](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/jpope/32/59425_2.png) [@jpope](https://forum.nachi.org/u/jpope)\ **Post date:** [June 26, 2007, 7:16pm UTC](https://forum.nachi.org/t/trap-question/17816/8 "2007-06-26T19:16:06Z")
That is a double trap, plain and simple. A tail-piece cannot be used as a vent, and a trap is not allowed to drain to another trap (with few exceptions). It’s wrong and should be corrected. ---
**Author:** ![ccurrins](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/ccurrins/32/225758_2.png) [@ccurrins](https://forum.nachi.org/u/ccurrins)\ **Post date:** [June 26, 2007, 7:22pm UTC](https://forum.nachi.org/t/trap-question/17816/9 "2007-06-26T19:22:34Z")
> [@dmacy](#): > > Is the trap needed at the dipsposal? Shouldnt a straight pipe be used. > > If there is a issue can someone explain or is this OK. If this is a Insinkerator Badger model, that is the way they recommend you install it. In their installation instructions it says ( if you have a double sink, use separate traps for both sides) That is how i installed mine and have had know problems. It has a 3 yr. warranty, so i put it in the way they wanted it. ---
**Author:** ![jpope](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/jpope/32/59425_2.png) [@jpope](https://forum.nachi.org/u/jpope)\ **Post date:** [June 26, 2007, 7:42pm UTC](https://forum.nachi.org/t/trap-question/17816/10 "2007-06-26T19:42:33Z")
> [@ccurrins](#): > > If this is a Insinkerator Badger model, that is the way they recommend you install it. > In their installation instructions it says ( if you have a double sink, use separate traps for both sides) That is how i installed mine and have had know problems. It has a 3 yr. warranty, so i put it in the way they wanted it. That is not the proper way to install the traps - period. Even if the manufacturer says “trap each sink separately,” this is not the way to do it. In areas where the IRC is used, a shared trap arm is allowed, but the traps are required to be at the same elevation and attached to the trap arm with a Wye or directional fitting, such as a back-to-back. In areas where the UPC is used, you cannot have a shared trap arm and must use a common trap (a single trap) regardless of the manufacturers recommendations. Where’s the vent for your sink Christopher? ---
**Author:** ![homebild](https://avatars.discourse-cdn.com/v4/letter/h/90db22/32.png) [@homebild](https://forum.nachi.org/u/homebild)\ **Post date:** [June 27, 2007, 2:01am UTC](https://forum.nachi.org/t/trap-question/17816/11 "2007-06-27T02:01:49Z")
Double-traps, as illustrated in the photo, is a plumbing code violation, and illegal, under the IRC/IPC plumbing regulations. Double trapping can break the trap seal and allow sewer gas to enter a house. Besides that, the trap for the garbage disposal is installed BACKWARDS \ and needs to be removed. ---
**Author:** ![jpope](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/jpope/32/59425_2.png) [@jpope](https://forum.nachi.org/u/jpope)\ **Post date:** [June 27, 2007, 2:06am UTC](https://forum.nachi.org/t/trap-question/17816/12 "2007-06-27T02:06:14Z")
> [@homebild](#): > > Besides that, the trap for the garbage disposal is installed BACKWARDS \ and needs to be removed. Yea, that too 😉 ---
**Author:** ![homebild](https://avatars.discourse-cdn.com/v4/letter/h/90db22/32.png) [@homebild](https://forum.nachi.org/u/homebild)\ **Post date:** [June 27, 2007, 2:07am UTC](https://forum.nachi.org/t/trap-question/17816/13 "2007-06-27T02:07:26Z")
> [@bwiley](#): > > In this case, probably nothing because the second sink drain acts as a vent in-between the traps. Two traps in the line though can act as an S-trap, or can cause poor drainage. > > In any case, it looks amateurish, which should raise red flags! 😉 The second sink drain would only act as a ‘vent’ if the sink is not filled with water. If it is filled with water, then one or both traps could siphon breaking the trap seal and allowing potentially harmful sewer gases into the structure. This is an illegal installation and needs to be corrected. Double-trapping as illustrated here is a code violation under most all plumbing codes. ---
**Author:** ![ccurrins](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/ccurrins/32/225758_2.png) [@ccurrins](https://forum.nachi.org/u/ccurrins)\ **Post date:** [June 27, 2007, 2:28am UTC](https://forum.nachi.org/t/trap-question/17816/14 "2007-06-27T02:28:20Z")
> [@homebild](#): > > The second sink drain would only act as a ‘vent’ if the sink is not filled with water. If it is filled with water, then one or both traps could siphon breaking the trap seal and allowing potentially harmful sewer gases into the structure. > > This is an illegal installation and needs to be corrected. > > Double-trapping as illustrated here is a code violation under most all plumbing codes. How about this type of installation? ---
**Author:** ![mthomas2](https://avatars.discourse-cdn.com/v4/letter/m/a87d85/32.png) [@mthomas2](https://forum.nachi.org/u/mthomas2)\ **Post date:** [June 27, 2007, 2:55am UTC](https://forum.nachi.org/t/trap-question/17816/15 "2007-06-27T02:55:01Z")
IMO, a lot of the confusion is the result of the InSinkErator instructions, specifically step 11.4 : “If you have a double sink, use separate drain traps for both sides.” here: [http://www.insinkerator.com/pdfs/US\_ICU1.pdf](http://www.insinkerator.com/pdfs/US_ICU1.pdf) ---
**Author:** ![pdickerson](https://avatars.discourse-cdn.com/v4/letter/p/3d9bf3/32.png) [@pdickerson](https://forum.nachi.org/u/pdickerson)\ **Post date:** [June 27, 2007, 4:10am UTC](https://forum.nachi.org/t/trap-question/17816/16 "2007-06-27T04:10:13Z")
> [@ccurrins](#): > > How about this type of installation? There is nothing wrong with that arrangement, provided that both traps are properly vented ---
**Author:** ![sparksnmore](https://avatars.discourse-cdn.com/v4/letter/s/c68b51/32.png) [@sparksnmore](https://forum.nachi.org/u/sparksnmore)\ **Post date:** [June 27, 2007, 5:11am UTC](https://forum.nachi.org/t/trap-question/17816/17 "2007-06-27T05:11:13Z")
> [@ccurrins](#): > > If this is a Insinkerator Badger model, that is the way they recommend you install it. > In their installation instructions it says ( if you have a double sink, use separate traps for both sides) That is how i installed mine and have had know problems. It has a 3 yr. warranty, so i put it in the way they wanted it. That isn’t double trapped even though there is only one outlet for two traps. “Double trapped” is when they’re in series, IE the water leaving the first trap enters the inlet of the second trap. Actually that situation is technically two “S” traps since they’re not properly vented. ---
**Author:** ![ccurrins](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/ccurrins/32/225758_2.png) [@ccurrins](https://forum.nachi.org/u/ccurrins)\ **Post date:** [June 27, 2007, 5:47am UTC](https://forum.nachi.org/t/trap-question/17816/18 "2007-06-27T05:47:03Z")
> [@sparksnmore](#): > > That isn’t double trapped even though there is only one outlet for two traps. > “Double trapped” is when they’re in series, IE the water leaving the first trap enters the inlet of the second trap. > Actually that situation is technically two “S” traps since they’re not properly vented. Where are you getting double trapped from? Serious ---
**Author:** ![homebild](https://avatars.discourse-cdn.com/v4/letter/h/90db22/32.png) [@homebild](https://forum.nachi.org/u/homebild)\ **Post date:** [June 27, 2007, 11:01am UTC](https://forum.nachi.org/t/trap-question/17816/19 "2007-06-27T11:01:32Z")
> [@ccurrins](#): > > How about this type of installation? That is not a double-trap situation since the traps are not in a series. ---
**Author:** ![jpope](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/jpope/32/59425_2.png) [@jpope](https://forum.nachi.org/u/jpope)\ **Post date:** [June 27, 2007, 3:01pm UTC](https://forum.nachi.org/t/trap-question/17816/20 "2007-06-27T15:01:06Z")
The picture in post 1 is a double trap - two traps in series. The picture in post 9 is not a double trap, but it’s still improper. [Next page](https://forum.nachi.org/t/trap-question/17816.md?page=2)