New Home Basement Bathroom Plumbing

[marndt]

I'm installing a basement bathroom group in a new home and have a few questions based on the attached basement plumbing layout.
1. Do I need a vent closer to the WC? If yes, how close? What is the code?
2. Is 1/8" pitch enough for a 3" line to a lift pump basket 60' away? That's about 7 1/2" drop plus a 4" concrete floor puts me about down 11 1/2"-12" to the basket inlet.
3. What else should I consider or change? Pump and basket location can not be moved closer.

 

[wwhitney]

Minnesota uses the UPC; I did not check for amendments.

1) Your lavatory drain can wet vent the WC if you meet a few restrictions. First, the lav drain and vent have to be 2" (as shown); the lav trap arm can be 1-1/2" or 1-1/4". Second, the WC drain, measured along the pipe both vertically and horizontally from the closet flange to the wye where the lav drain comes in is limited to 6'.

2) The UPC requires 1/4" per foot slope for all drains. If you upsize the drain to 4" after all the fixtures, and you get permission from the AHJ on the basis that the pit would just be too deep otherwise, then you could use 1/8" per foot slope on the 4" portion.

Chapter 7 Sanitary Drainage: Sanitary Drainage, 2020 Minnesota Plumbing Code | UpCodes

UpCodes offers a consolidated resource of construction and building code grouped by jurisdiction

up.codes

3) You show a vent line coming off the 3" line between the lav connection and the shower connection. That vent connection is not useful in that location, and your shower is unvented. With the connectivity order shown, the shower can not be wet vented, as the WC needs to be the last fixture on the wet vent. So you would need to move that extra dry vent to connect to the shower trap arm before the shower connects to the 3" line. And that horizontal jog you show in the vent would need to be at least 6" above the fixture flood rim (the shower curb in this case). Vent sections at 45 degrees from vertical are still considered vertical.

Also, just to double check, there can be no drainage coming down the dashed vent line from the story above. It needs to rise to the bathroom above and join a dry vent in that bathroom, one that is at least 2".

Lastly, I'm a little unclear on the cleanout requirements: whether it's OK not to have a cleanout for the portion of 3" drain between the WC and the wye where the lav drain joins; and whether the cleanout at the lav should be 3" (meaning the downstream drain would also be 3").

Cheers, Wayne

 

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[marndt]

Minnesota uses the UPC; I did not check for amendments.

1) Your lavatory drain can wet vent the WC if you meet a few restrictions. First, the lav drain and vent have to be 2" (as shown); the lav trap arm can be 1-1/2" or 1-1/4". Second, the WC drain, measured along the pipe both vertically and horizontally from the closet flange to the wye where the lav drain comes in is limited to 6'.

2) The UPC requires 1/4" per foot slope for all drains. If you upsize the drain to 4" after all the fixtures, and you get permission from the AHJ on the basis that the pit would just be too deep otherwise, then you could use 1/8" per foot slope on the 4" portion.

Chapter 7 Sanitary Drainage: Sanitary Drainage, 2020 Minnesota Plumbing Code | UpCodes

UpCodes offers a consolidated resource of construction and building code grouped by jurisdiction

up.codes

3) You show a vent line coming off the 3" line between the lav connection and the shower connection. That vent connection is not useful in that location, and your shower is unvented. With the connectivity order shown, the shower can not be wet vented, as the WC needs to be the last fixture on the wet vent. So you would need to move that extra dry vent to connect to the shower trap arm before the shower connects to the 3" line. And that horizontal jog you show in the vent would need to be at least 6" above the fixture flood rim (the shower curb in this case). Vent sections at 45 degrees from vertical are still considered vertical.

Also, just to double check, there can be no drainage coming down the dashed vent line from the story above. It needs to rise to the bathroom above and join a dry vent in that bathroom, one that is at least 2".

Lastly, I'm a little unclear on the cleanout requirements: whether it's OK not to have a cleanout for the portion of 3" drain between the WC and the wye where the lav drain joins; and whether the cleanout at the lav should be 3" (meaning the downstream drain would also be 3").

Cheers, Wayne

Thanks, Wayne,

Strangely, there is no building or plumbing inspection where I'm building this. I wish there was, so that's why I'm reaching out to this forum and people like yourself to do what I can to get this right. I updated my drawing based on your feedback. Let me know If I understood you correctly.

 

[Tuttles Revenge]

If you move the shower trap arm to the branch serving as the wet vent / BAS drain, you can eliminate the individual shower vent altogether. If you upsize that branch to the BAS to 3" that gives you your end of line cleanout, so long as the toilet is within 5ft of that branch.

 

[marndt]

Forgot to add. I was thinking about maybe running a vanity or shower drain down from upstairs to this drain line to add some more "gray" water to the line. I know this would add more water to the lift basket in the basement but thought a bit more water on a low slope line might help. I guess there are some trade-offs, but I'm interested in your thoughts. While we are living here that basement bathroom won't get used much, but who knows down the line when someone owns the home.

 

[Tuttles Revenge]

This is how I would run the basement bathroom individually. Shorten up the length of the WC trap arm so its within 5ft of the end of line cleanout path.

If you have the opportunity to run any fixtures gravity... run them gravity. its technically required in the UPC, but it works when the power goes out. But if you do just feel like adding those fixtures to this drain, they must connec downstream of the horizontal wet vented system. And if you just happen to feel like your kitchen drain must dump into a sewage ejector... make sure you have a way to handle the grease, it will gum up the works of the sump.

 

[wwhitney]

I updated my drawing based on your feedback.

Your updated drawing is fine, other than the cleanout question. But it does use 3 separate dry vent takeoffs, so the venting is more trouble. Tuttle's drawing uses wet venting to reduce that to one 2" dry vent takeoff at the lav.

Cheers, Wayne

 

[marndt]

This is how I would run the basement bathroom individually. Shorten up the length of the WC trap arm so its within 5ft of the end of line cleanout path.
View attachment 91989
If you have the opportunity to run any fixtures gravity... run them gravity. its technically required in the UPC, but it works when the power goes out. But if you do just feel like adding those fixtures to this drain, they must connec downstream of the horizontal wet vented system. And if you just happen to feel like your kitchen drain must dump into a sewage ejector... make sure you have a way to handle the grease, it will gum up the works of the sump.

This is how I would run the basement bathroom individually. Shorten up the length of the WC trap arm so its within 5ft of the end of line cleanout path.
View attachment 91989
If you have the opportunity to run any fixtures gravity... run them gravity. its technically required in the UPC, but it works when the power goes out. But if you do just feel like adding those fixtures to this drain, they must connec downstream of the horizontal wet vented system. And if you just happen to feel like your kitchen drain must dump into a sewage ejector... make sure you have a way to handle the grease, it will gum up the works of the sump.

This is how I would run the basement bathroom individually. Shorten up the length of the WC trap arm so its within 5ft of the end of line cleanout path.
View attachment 91989
If you have the opportunity to run any fixtures gravity... run them gravity. its technically required in the UPC, but it works when the power goes out. But if you do just feel like adding those fixtures to this drain, they must connec downstream of the horizontal wet vented system. And if you just happen to feel like your kitchen drain must dump into a sewage ejector... make sure you have a way to handle the grease, it will gum up the works of the sump.

Thanks for feedback! So from the clean-out onward would be 3". I will need to check to see if I can hit the 5 ft mark.

 

[marndt]

This is how I would run the basement bathroom individually. Shorten up the length of the WC trap arm so its within 5ft of the end of line cleanout path.
View attachment 91989
If you have the opportunity to run any fixtures gravity... run them gravity. its technically required in the UPC, but it works when the power goes out. But if you do just feel like adding those fixtures to this drain, they must connec downstream of the horizontal wet vented system. And if you just happen to feel like your kitchen drain must dump into a sewage ejector... make sure you have a way to handle the grease, it will gum up the works of the sump.

It would be just vanity or shower. Just seem like a bit more "clean" water would be beneficial, but maybe I'm wrong. The kitchen is on the other side of the building and will be gravity feed. We are on a septic system so we are very careful about grease getting into the plumbing system.

 

[Tuttles Revenge]

Honestly a 6ft run vs a 5ft run isn't a deal breaker.. If I had to pass a plumbing inspection in Bellevue, it would be dead on.. but if I got it in Seattle, I would just show the inspector that I couldn't get it and he would shrug and we would move on. The difference is that a handheld toilet auger is supposed to reach to 5ft past the toilet.. so your end of the line cleanout takes over from there.. But really, we don't see much snaking in modern plastic piping unless something gets screwed up.

 

[marndt]

Your updated drawing is fine, other than the cleanout question. But it does use 3 separate dry vent takeoffs, so the venting is more trouble. Tuttle's drawing uses wet venting to reduce that to one 2" dry vent takeoff at the lav.

Cheers, Wayne

Anyone have any thoughts on putting in a backwater valve in the 4” PVC. I’m guessing it would installed right before it dumps into the lift station basket.

 

[Tuttles Revenge]

I avoid backwater valves as much as possible. They introduce additional failure points AKA clogs to the drain. However if you're prone to backups then by all means protect your house from that.. Just check on it on a regular basis to determine what maintenance schedule you need to keep it running smoothly.