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Robbb · Feb 1, 2008, 10:35 PM

I'm planning on putting in a bathroom (shower, toilet, lav) in the basement of our house. I have a question regarding drainage:
Is there a minimum drop in elevation needed from a fixture to the main sewer line? I have the necessary 1/4" per foot of line slope, but the total drop from the shower drain to the main sewer line will only be about 6 inches. The connection with the main line will be at an existing elbow at the bottom of the main trap. (FYI - an existing floor drain is currently connected at this point and is causing no problems)

Thanks

massplumber2008 · Feb 2, 2008, 07:01 AM

Plumbing code requires 1/4"/ft for 3" pipe and smaller as you suggested, but there is no minimum drop requirements... if you have any concerns about backflow for any reason can always install a backwater valve in the main drain picking up the new bathroom (must be accessible for future).. but it really is not necessary at all (I install these in wetlands and areas where city sewer cleaners flush problem lines all the time). Just pipe it all up according to code and you should be just fine! Good luck!

speedball1 · Feb 2, 2008, 07:20 AM

the total drop from the shower drain to the main sewer line will only be about 6 inches.

This concerns me. Why do you have a 24' run from the shower to the main? Or is this the drop for the entire bathroom group? Most bathroom groups are roughed in like this.
Toilet connects to sewer main or the stack vent. 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. The vent off the lavatory may be run out the roof or revented back into a dry vent in the attic or if you're reventing back into a fixtures dry vent you must make your connection at least 6 inches over that fixtures flood rim. 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. Good luck, Tom.

Robbb · Feb 2, 2008, 10:05 AM

Thanks for the input guys. The reason I asked the question is that I had a plumber doing some other work in my house a couple of years ago and he took a look at the situation. He said that I would need more drop, but that I could still install a toilet (no shower) if I put in a wall hung/tanked unit.

Speedball, about 4" of that total 6" drop that I mentioned will be slab, so I have about 2" for drainline sloping (which should be enough considering it's a smaller bathroom).

Regarding the layout you described: I can see why the ideal situation is to have the toilet at the downstream end of the waste line, but is it still OK to have the shower at the downstream end with the toilet in the middle (i.e. shower connects to sewer main, toilet drains to shower drain and lav drain ties into toilet drain - all correctly sized and vented of course!).

Anyway, I plan on having a plumber come out this week to verify. Thanks again.

massplumber2008 · Feb 2, 2008, 10:48 AM

Robb... is this pipe sticking out of the slab..

Robbb · Feb 2, 2008, 11:28 AM

massplumber2008 - No, I haven't installed any of the bathroom's plumbing yet. I've broken open the slab and the base of an adjacent concrete wall. Under the slab is a 2" line from a floor drain. This drains under the wall and ties into an elbow at the bottom of the main stack.

My plan is open up the slab to put in the drain lines for the bathroom. I'll pull the floor drain line out and tie the bathroom drain line in to the bottom of the stack (at the same location the drain lie tied in).

speedball1 · Feb 2, 2008, 12:03 PM

[QUOTE][Regarding the layout you described: I can see why the ideal situation is to have the toilet at the downstream end of the waste line, but is it still OK to have the shower at the downstream end with the toilet in the middle (i.e. shower connects to sewer main, toilet drains to shower drain and lav drain ties into toilet drain - all correctly sized and vented of course!)./QUOTE]
Of course you may configure your group any way you wish. I gave you a typical rough. However, You will have to vent these fixtures the regular way instead of wet venting any of them. Good luck, Tom