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Thread: lavatory drain question

  1. #1
    DIY Junior Member thezster1's Avatar
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    Default lavatory drain question

    New pedestal sink... has 1 1/4 tailpiece. Out of wall is 1 1/2 PVC to drain. What size should the P-trap be to meet code requirements.

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    Plumber jimbo's Avatar
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    A 1 1/4" P trap is fine for a lavatory sink, but my preference is to use 1. On a pedestal, the smaller one is easier to manuever and possibly just looks a little neater.

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    DIY Junior Member thezster1's Avatar
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    I agree with you 100% on both points. I put in the 1 1/4 trap with a reducer on the 1 1/2 out of the wall. IThis is the second "violation" pointed out by my plumber today.... I can't figure him out......

  4. #4
    Moderator & Master Plumber hj's Avatar
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    There is no "code" requirement. An 1 1/4" trap has a shorter "U" bend radius so it will usually fit better. We ALWAYS have 1 1/2" out of the wall, but use a 1 1/4" chrome trap when it will be exposed and 1 1.2" plastic inside cabinets. IF a "plumber" failed you, then he is either not knowledgeable or he is just trying to give you a hard time.

  5. #5
    Plumber jimbo's Avatar
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    As far as the actual code requirement, the UPC specifies the minimum trap and trap arm size for a single lav. sink as 1 1/4".

  6. #6
    Moderator & Master Plumber hj's Avatar
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    My comment was to imply that there was no code requirement that would preclude the 1 1/4" trap or require the 1 1/2" trap at that location.

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    DIY Junior Member thezster1's Avatar
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    Thanks guys... My knowledge - as a "regular person/contractor" allows the 1 1/4 trap..... which I did - for ease of installation as well as aesthetic purposes..... I just wonder - I think my licensed plumber does a majority of his work for commercial applications...... would that explain why he told me a 1 1/2 inch trap was necessary? I know the rules differ from residential to commercial... but am not familiar with the specifics...

  8. #8
    Moderator & Master Plumber hj's Avatar
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    1 1/4" trap are more common in commercial applications than residential because most of them are exposed. Your "plumber" may be one who only installs the "rough" plumbing in a building and NEVER even sees the final stage.
    Last edited by hj; 03-13-2010 at 03:33 PM.

  9. #9
    DIY Junior Member thezster1's Avatar
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    Your assessment of the plumber is correct.... he does my rough ins... and I finish up for the finals.... Thanks guys - I'm going to leave the smaller trap - and see what the inspector says...... I'm a busy amateur - never claimed to be a plumber - though I can plumb a whole house if need be ----- and can't help but wonder - if a 1 1/4 trap doesn't meet code --- why on earth would they be available for sale...... LOL

  10. #10
    Moderator & Master Plumber hj's Avatar
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    IF they can sell something, then they could care less about whether it meets "code" or not, and many items do not. Rough plumbers are exactly that. They usually have ZERO knowledge of what happens once they leave the job. In fact, many of them do not even know why they have to install cleanouts, or where they should be to make servicing the system easier. Which could be a problem at a house where I was yesterday, unless the plumber did install a cleanout, but did not make sure the sheetrockers would not cover it up.

  11. #11
    DIY Junior Member thezster1's Avatar
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    Hahaha.... Love the reference.... Just finishing up my current rehab project - and the electrician asked me - after the drywall went up - why there were no switches in one of the bedrooms...... (but there was a slight "bow" in the drywall next to the door..)..... LOL

    Thanks for the help...

  12. #12
    Moderator & Master Plumber hj's Avatar
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    They would have loved a job a DIYer wired in Grand Rapids MI. He pulled the Romex right through one side of the box and out the other, (No loop). After it was all drywalled and painted he called an electrician to install the receptacles and switches. When he saw the job he told the guy that he did not have enough money for him to do the job. There was not even enough wire in the boxes to crimp pigtails on to extend the wires. Another one use 14/3 between a three way and four way switch. When I told him he needed four wires he asked if you could use the bare neutral as the fourth one.

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