Robert Ellenberg
Registered User
I have built and designed houses for over 30 years and have always studied the codes—except plumbing. I have relied on the plumber who was doing the work to properly size and run the DWV system and I had very limited knowledge of how or why it needed to be a certain way.
For the past 3-4 years I have been working part time designing a unique concept “kit” house. The plans (intent) is to have the structure pre assembled as weather tight modules and include all materials needed to complete the house, pre sell them and ship them to different parts of the country. That means that in many jurisdictions they will need to exceed the IRC standards. I am working on the designs for the plumbing DWV systems so over the past few months I have been studying in an effort to gain the knowledge needed to design them to meet the strictest codes.
I have come up with an unusual way to tie the vents together and I believe it meets the codes, but because I can’t find anything quite like it to compare it to—I am not sure. My question relates to how I propose to run the vents in regards to some unique features of the designs. These are small one story homes with conditioned crawl spaces (no slabs) with one or two baths. To increase the usable interior volume, most of the interior partitions will be unique prebuilt panels only 2.5” thick—not enough for drains or vents in most of the walls. We will thicken them or make a chase where necessary to run vents up. However, they cannot be tied together above the ceiling line for a single exit through the roof because the flat ceiling-roof structure will be filled solid with foam (no attic or space of any kind) and we don’t want a roof peppered with numerous vents.
I want to try and explain how we intend to do it and I would like to know if it sounds as if it meets all of the codes relating to drains and vents. My question only relates to routing as I know you can’t comment on pipe sizing etc., without more information.
The tub and shower drains and traps will be in the crawl space. I want to take the sinks and laundry stand pipe through their traps in the cabinets and drop the drains straight through the floor (is this permitted as long as the trap is close enough to the bottom of the sink drain?). Under the house, take all of the properly sloping drains under the floor from the individual fixtures and tie them into a main horizontal drain pipe that is sized correctly and has the toilets tied in as well. The high end of that main drain would be a 3” pipe with a sweep and clean out plug and the sweep turns upward taking a 3” vent up a chase and through the roof. We will then have an individual vent pipe connected to each drain line within the crawl space, connected to the top centerline within the prescribed distance from the fixture trap, immediately going into a 90 bend and sloping upward at ¼” /foot (under the floor in the crawl space), all converging on the chase where the 3” vent from the end of the drain goes up through the roof. Turn the vent pipes up inside the chase (90 turn upward) and take the individual vents up to a height at least 6” above the flood rim of the fixture they serve and tie them into the 3” vent. Here is another way to explain it: you normally take individual vents up to the attic, make a 90 and take them on an upward slope of 1/4"/foot to where they tie in to the large vent pipe and exit the roof. I am proposing to do it in a similar way except run them under the floor instead of in the attic over to the chase and then get them above the fixture rim flood height before tying them into the 3" vent that exits through the roof.
If I haven’t given enough information for some of you master plumbers/inspectors to answer, post questions and I will try to respond. And remember, I am not a plumber or plumbing inspector but a designer-builder trying to get it right before it is built and you come out to look at it!
For the past 3-4 years I have been working part time designing a unique concept “kit” house. The plans (intent) is to have the structure pre assembled as weather tight modules and include all materials needed to complete the house, pre sell them and ship them to different parts of the country. That means that in many jurisdictions they will need to exceed the IRC standards. I am working on the designs for the plumbing DWV systems so over the past few months I have been studying in an effort to gain the knowledge needed to design them to meet the strictest codes.
I have come up with an unusual way to tie the vents together and I believe it meets the codes, but because I can’t find anything quite like it to compare it to—I am not sure. My question relates to how I propose to run the vents in regards to some unique features of the designs. These are small one story homes with conditioned crawl spaces (no slabs) with one or two baths. To increase the usable interior volume, most of the interior partitions will be unique prebuilt panels only 2.5” thick—not enough for drains or vents in most of the walls. We will thicken them or make a chase where necessary to run vents up. However, they cannot be tied together above the ceiling line for a single exit through the roof because the flat ceiling-roof structure will be filled solid with foam (no attic or space of any kind) and we don’t want a roof peppered with numerous vents.
I want to try and explain how we intend to do it and I would like to know if it sounds as if it meets all of the codes relating to drains and vents. My question only relates to routing as I know you can’t comment on pipe sizing etc., without more information.
The tub and shower drains and traps will be in the crawl space. I want to take the sinks and laundry stand pipe through their traps in the cabinets and drop the drains straight through the floor (is this permitted as long as the trap is close enough to the bottom of the sink drain?). Under the house, take all of the properly sloping drains under the floor from the individual fixtures and tie them into a main horizontal drain pipe that is sized correctly and has the toilets tied in as well. The high end of that main drain would be a 3” pipe with a sweep and clean out plug and the sweep turns upward taking a 3” vent up a chase and through the roof. We will then have an individual vent pipe connected to each drain line within the crawl space, connected to the top centerline within the prescribed distance from the fixture trap, immediately going into a 90 bend and sloping upward at ¼” /foot (under the floor in the crawl space), all converging on the chase where the 3” vent from the end of the drain goes up through the roof. Turn the vent pipes up inside the chase (90 turn upward) and take the individual vents up to a height at least 6” above the flood rim of the fixture they serve and tie them into the 3” vent. Here is another way to explain it: you normally take individual vents up to the attic, make a 90 and take them on an upward slope of 1/4"/foot to where they tie in to the large vent pipe and exit the roof. I am proposing to do it in a similar way except run them under the floor instead of in the attic over to the chase and then get them above the fixture rim flood height before tying them into the 3" vent that exits through the roof.
If I haven’t given enough information for some of you master plumbers/inspectors to answer, post questions and I will try to respond. And remember, I am not a plumber or plumbing inspector but a designer-builder trying to get it right before it is built and you come out to look at it!
