Do I have to redesign this bathroom for this code?


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I hate to admit that I got this far (almost done with the construction docs) and now may have to redesign the master bath.  After working on the MEP and reading through the IRC, I found the spec for max distance of fixture trap from vent (6' for 1.5" pipe, 8' for 2" pipe, and 12' for 3" pipe.)

 

With the master bath layout shown, I'll have to put the 3" vent in an external wall next the the sink (shown in green) to meet the 6' to 1.5" trap (restricted by the window). The distance from the proposed vent to the tub trap would be slightly over 8' and slightly over 12' to the toilet trap.

 

I'm I missing something or you just can't have big bathrooms?   This is a bathroom floor plan I found online and liked.  The room above is a master bedroom/closet and the room below is the garage.  What would you do?

 

bathroom.pdf

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16 hours ago, DrawingABlank said:

You could just plan to vent them separately until they can reconnect in the attic or in this case the floor system.

 

Ok, so that's how you get around the code restriction. This approach takes more material.   Would that also be better than routing a drain vent horizontally under the window (going thru king studs)?  If I move the window... butted up against the wall, I can move the main vent closer to the bath and toilet and meet the code.  I'm not sure if it's a good idea to butt a window up to a wall.

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If you need to run the Arm 8' use a 2" arm. You can still use a 1.5" trap. You have to measure from the weir.

If you need less than 5' of arm use 1.5" pipe.

 

Make the wall thicker if the 1.5" arm is a structural issue.

 

If that doesn't work for you some jurisdictions allow an "Auto Vent" to be used inside the vanity.

This is how I would layout the piping.

 

Bath plu.JPG

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If you put the stack directly behind the lavatory you often conflict the vent stack with the light electrical box above the vanity.

So you have a very short arm or the have to offset the stack pipe below the light fixture.

Bath Plu2.JPG

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54 minutes ago, SkullMesaRanch said:

 

Would that also be better than routing a drain vent horizontally under the window (going thru king studs)?

Looks like due to the height of the window the horizontal vent under the window will not work. The vent needs to raise above the sink 'full line' before moving horizontal. (Limits 'dirty vent' should sink ever plug up.)

 

Sure there are a few more fittings and a stick of 1.5" but that is the trade off sometimes for design preferences. I would vent the sink by itself up into floor system before trying to tie it to a 3" vent in an exterior wall. (harder to insulate properly)

 

Alan has a good reminder on keeping clear of other needed MEP in the wall.

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You guys are really helpful.  I've been given a few options and even got an isometric from Alan.   I'm confident I can now come up with a solution to this without changing the layout of the master bath.  It's looking like a smaller window would help but a separate vent for the sink will solve the problem without any mods.  Thank you, all!

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