Hi all,

I'm new here so here's a little background before I ask my question. I'm a retired Naval Officer and I'm building my own home in Michigan. The framing is done and I'm wrapping up the exterior before the weather turns and I'm just about to start the plumbing rough in. My question is about the highest fixture rule for stack vents. My reference book (The Ultimate Guide To Plumbing) counterdicts it's self. It states that only the highest fixture or fixtures on a vent stack can be stack vented. It states that if you use a "Tee" you can vent more than one fixture because they enter the stack at the same level. Then in the various examples of typical plumbing installations, they routinely show a stack vented bath lavatory entering the stack above stack vented shower and toilet. These fixtures are all from the same bath. Isn't the lav the highest fixture which dictates that the shower and toilet have to be vented by some other means?

Thanks
Andy

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Isn't the lav the highest fixture which dictates that the shower and toilet have to be vented by some other means?

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Your lavatories can arm out to the vent stack, (which becomes a stack vent once you tie to it) providing the arms are 2" and not over 5 feet from the stack. However, The shower will have to have its own vent and if local codes dictate so will your toilet. If wet vents are allowed in your area you can get by by installing your bathroom group like this. Toilet connects to the vent stack. Lavatory connects to toilet drain and runs a vent off the top the stubout tee out the roof or revents back into a dry vent in the attic.. The toilet wet vents through the lavatory vent and the tub/shower connects to the lavatory drain and is wet vented by it. This is a normal rough in and is acceptable both by local and state codes and also The Standard Plumbing Code Book in 90 percent of the country. Check your local codes to make sure you're not in the excluded 10 percent.. The vent off the lavatory may be run out the roof or revented back into a dry vent in the attic. Good luck, Tom

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Originally Posted by speedball1

Your lavatories can arm out to the vent stack, (which becomes a stack vent once you tie to it) providing the arms are 2" and not over 5 feet from the stack. However, The shower will have to have its own vent and if local codes dictate so will your toilet. If wet vents are allowed in your area you can get by by installing your bathroom group like this. Toilet connects to the vent stack. Lavatory connects to toilet drain and runs a vent off the top the stubout tee out the roof or revents back into a dry vent in the attic..The toilet wet vents through the lavatory vent and the tub/shower connects to the lavatory drain and is wet vented by it. This is a normal rough in and is acceptable both by local and state codes and also The Standard Plumbing Code Book in 90 percent of the country. Check your local codes to make sure you're not in the excluded 10 percent.. The vent off the lavatory may be run out the roof or revented back into a dry vent in the attic. good luck, Tom

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Tom,

Thanks for getting back to me so quickly. I understand your suggested layout and it might work for me. I have some very tight spaces to work in so it might take some imagination to make it all fit.

Andy

Tom advice is dead on. Even though my state is under upc( the lost ten percent) my state has also been adopting new codes that overide upc. Wet venting of bathroom fixtures being one of them(thank god). Don't know your local codes( is it being inspected?) I would rough in as Tom suggested and you will not have any issues. Good luck and keep us posted.

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Originally Posted by mygirlsdad77

tom advice is dead on. Even though my state is under upc( the lost ten percent) my state has also been adopting new codes that overide upc. wet venting of bathroom fixtures being one of them(thank god). Dont know your local codes( is it being inspected?) I would rough in as Tom suggested and you will not have any issues. Good luck and keep us posted.

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My plumbing inspector just returned my call from earlier today. She is kind enough to stop by on Monday to take a look at my situation and give me some pointers before I start drilling holes. Now that's what I call a public servant! I'll pass on what she has to say but I'm pretty sure you guys have already told me what she is going to recommend.

Thanks again
Andy

Good to hear, she will clear up any issues. May I suggest coffee and donuts, just to get off on the right foot. Never hurts to keep the inspector happy. Good luck and please do keep us posted.

[QUOTE=mygirlsdad77;1325181]tom advice is dead on. Even though my state is under upc( the lost ten percent) my state has also been adopting new codes that overide upc. Wet venting of bathroom fixtures being one of them(thank god). QUOTE]

Sure am glad to hear that. Hpw about, washer surge pipes? And while we're on the subject why won't UPC allow washer traps top be installed as close to the floor as possible. I'm not even going to mention the Great Air Gap Debate.
Regards and thanks for the update, Lee. Tom

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Originally Posted by woodys3b

My plumbing inspector just returned my call from earlier today. She is kind enough to stop by on Monday to take a look at my situation and give me some pointers before I start drilling holes. Now that's what I call a public servant! I'll pass on what she has to say but I'm pretty sure you guys have already told me what she is going to recommend.

Thanks again
Andy

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Our plumbing Inspectors NEVER return calls...

Just to follow up after the visit from the inspector, I will be doing the drain/vents like this:

Rather than continuing the vertical main drain from below the slab all the way up throuth both floors, attic and out the roof, it will turn 90 degrees and start running horizontally just under the bathroom group on the second floor. It will run below the floor joists towards the center of the house. The tub/shower will be the first fixture to enter this 3" drain after it starts to run horizontal. Then the toilet enters via a 3 X 3 "y" fitting. Next comes a 3 X 2 reducer and then the Lav enters. The Lav is vented from above via attic and out the roof. So, while I never got a real answer about this highest fixture rule, I have an easier solution and I don't have to worry about the highest fixture.

Thanks for the help
Andy

[QUOTE=speedball1;1326733]

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Originally Posted by mygirlsdad77

tom advice is dead on. Even though my state is under upc( the lost ten percent) my state has also been adopting new codes that overide upc. wet venting of bathroom fixtures being one of them(thank god). QUOTE]

Sure am glad to hear that. Hpw about, washer surge pipes? And while we're on the subject why won't UPC allow washer traps top be installed as close to the floor as possible. I'm not even gonna mention the Great Air Gap Debate.
Regards and thanks for the update, Lee. Tom

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Long story short. Yes I'm under upc in general. But my state has adopted many parts of other codes. When all is said and done, upc doesn't really hold up anywhere because its all about the authority having jurisdiction(meaning local inspector has the final say). I have an awesome inspector that realizes that you can only do so much with limited room. Traps can be as close to floor as possible (just leave and inch or so for installation of glued trap). And running fifteen foot for a washer drain before tying in to any other drain is near impossible in a residential home. So most inspecters don't even enforce this crazy UPC. As far as air gaps go, there is a good reason for them.