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Main drain size for basement bathroom

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  • Main drain size for basement bathroom

    Yet again. I know. I've been searching threads for a couple of days now and have come up with the (we can't do that honey) excuse I've been looking for, but I've got to be sure.


    My parents are moving in to our home which currently has a legal in-law apt. After 30 years of tension and irritation they turned into the perfect couple once my mother got her own bathroom, so in the interest of maintaining sanity I'd like to add a bathroom to our basement where my Dad's room/getaway/mancave will be. I'm planning on doing a majority of the grunt work myself, and my friend(15 yr master plumber) doing design/connections and inspection. He told me to get a plan together and then call him. I pay him $100/on-site consultation. I'm also a well-paid tech who likes to know the how and the why. We've been swapping the same $100 back and forth for 5 years now. Keeps us both honest.

    I
    Our town is under the 2000 IRC and the 2000 IPC.
    We've got 3 1/2 baths, 1 diswasher, 2 kitchen sinks, 1 washer all draining into a 3" pvc main drain to a 4" cleanout that then heads toward the septic. THE DRIAIN is ONLY 6" ABOVE BASEMENT GRADE!!!!!!!!!!! I'VE GOT MORE THAN ENOUGH SLOPE TO THE SEPTIC WHY WHY WHY WHY!!!!!! I guess so the plumber wouldn't have to box the cleanout in the floor. OK I KNEW THAT ONE. So back to the ejector pump question.

    The 3" was a red flag when I inspected the home before purchase but at that time I didn't think the folks would be comming to stay and necessitate an extra bath and my guestimate on flush units said I was ok. If I'm going to drain into the existing house drain I would almost always need to drain into a 4" right? My thought is to run a 3" drain from the pump to the cleanout and combine both 3" to a new 4" stack.

    I don't know which one would be worse/better in the long run. The basement is currently finished, and the original 3" drain is boxed into a drywalled soffit wrapping the whole basement and would just be a PINA to replace. Running a new 3" to the cleanout and combining there is almost as bad.

    This pluming stuff sure seems like a lot of work, huh?
    Last edited by nhmatt; 02-16-2009, 11:04 AM.

  • #2
    Re: Main drain size for basement bathroom

    UPC only allows 3 water closets on 3".A new 4" drain would be better.

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    • #3
      Re: Main drain size for basement bathroom

      they make a toilet system that has a macerating pump inside a floor mounted tank. this also lets you drain other bathroom fixtures into the tank. the discharge line can be as small as 3/4'' pvc. and it can pump uphill

      don't have the name handy, but my supply house has one on display.

      rick.
      phoebe it is

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      • #4
        Re: Main drain size for basement bathroom

        That seals it. 4" pipe it is, or will be depending on what a crab my mother turns out to be.

        Venting to the roof is another challenge. I know I need a seperate vent for the ejector pump (2"I guessing) but is 2" large enough to vent a shower, toilet sink and washer? I would need some horizontal runs about 20' total, and from what I've been able to gather here in a few hours anything more than 3' means I'd have to upsize to a 3" vent, which doesn't snake too well inside a 2x4 stud wall.

        Once I tell the wife what I'm going to have to do to her beautiful house in order to get this done I'm guessing I'll have the Summer off!

        Comment


        • #5
          Re: Main drain size for basement bathroom

          Originally posted by PLUMBER RICK View Post
          they make a toilet system that has a macerating pump inside a floor mounted tank. this also lets you drain other bathroom fixtures into the tank. the discharge line can be as small as 3/4'' pvc. and it can pump uphill

          don't have the name handy, but my supply house has one on display.

          rick.
          I don't even like the idea of the sewege ejector pump. If the basement floor wasn't tiled I swear I'd jack up the whole floor, punch out under teh footing, repipe to the septic tank and drop the drain below the floor, cleanout and all. I'm always looking for excuses to rent a mini excavator.

          That being said this is going to be a low-use bathroom, probably more along the lines of a guest bathroom so I REFUSE to go crazy over it. I have been to the Valley of never-ending home improvement and made it out alive. I'm not searching for an excuse to do it wrong but if I was in the plumbing business I'd have to guess $20,000+, and I can listen to a whole lot of bitchin' for $20,000.
          Last edited by nhmatt; 02-16-2009, 11:58 AM.

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          • #6
            Re: Main drain size for basement bathroom

            slow down. this entire system is above ground. the toilet has a rear outlet. the toilet tank/ macerator pump sits inside the toilet tank and is self contained. basically plug and play.

            the discharge line is 3/4'' pvc and the tank has the ability to accept waste from a sink, tub, and shower if you elevate the shower drain.

            i believe the entire system including the toilet is under $2000.

            not too sure of the venting requirements of the toilet tank/ pump. but the entire system doesn't require any saw cutting/ jack hammering. sorry but you don't need the mini excavator

            rick.
            phoebe it is

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            • #7
              Re: Main drain size for basement bathroom

              Originally posted by nhmatt View Post
              That seals it. 4" pipe it is, or will be depending on what a crab my mother turns out to be.

              Venting to the roof is another challenge. I know I need a seperate vent for the ejector pump (2"I guessing) but is 2" large enough to vent a shower, toilet sink and washer? I would need some horizontal runs about 20' total, and from what I've been able to gather here in a few hours anything more than 3' means I'd have to upsize to a 3" vent, which doesn't snake too well inside a 2x4 stud wall.

              Once I tell the wife what I'm going to have to do to her beautiful house in order to get this done I'm guessing I'll have the Summer off!
              You have some unique tidbits of info
              1.More than three feet...20' overall offset is O/K(UPC)
              2.Why would one need to snake a vent back to a sump?
              3.2" vent is adequate(UPC)

              Does IPC have that many differences from UPC?

              Comment


              • #8
                Re: Main drain size for basement bathroom

                I don't like pumps. Pumps go bad. Gravity is always there for you, doesn't care how hot or cold it is, whether or not the power is working, when you installed it, or what the mark-up on replacement parts is at the local supply house. My sister's whole neighborhood is on pumps- LET'S PUT A HOUSE WHERE NO ONE ELSE THOUGH IT WAS A GOOD IDEA!!!!!

                No, I'm not crazy, and I looked at the macerating toilets but it still comes down to the problem I have with a 3" drain and too many flush units.

                Comment


                • #9
                  Re: Main drain size for basement bathroom

                  [quote=drtyhands;209320]You have some unique tidbits of info
                  1.More than three feet...20' overall offset is O/K(UPC)
                  2.Why would one need to snake a vent back to a sump?
                  3.2" vent is adequate(UPC)

                  quote]
                  Maybe snake is the wrong word to use in plumbing forum, but I'm a wire jockey at heart.

                  From what I've been able to gather so far a sewege ejector pump shall have its own vent that penetrates the roof independent of any other plumping in the house. My pump says 1 1/2, but I was going to upsize anyway because of the horizontal runs.

                  20' overall offset: I read late last night in-between glasses of wine that 2" minimum for a water closet, and if the horizontal run was more than 3' you had to incrase the diameter of the pipe 1 trade size (3"). Am I thinking of wet-venting?

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