New Sewer Line for Granny Unit
Putting together costs for building a “granny unit” behind a clients house. The structure is about 25 feet away from the main house in the back yard. The main house is on city sewer.
The only way I see to tie into the the existing sewer line is to install a sump pump at the “granny unit” and then run a 3″ line to the main house and tie into the sewer line there.
I guess you could also use a macerating toilet, and install a leach field for the shower and the sink, but that sounds expensive.
I'm guessing that the finished floor of the proposed "granny unit" is below the FF of the main house and likewise for the main soil pipe exiting both structures?
I'd be surprised if any kind of leach field was allowed in an area that has city sewer. Also, just as an FYI I think that sewage injection pumps are often connected to out-feed pipes of a smaller diameter than 3" - say 2.5". I may be wrong about this, and I'm sure someone will correct me if I am. Also, a backflow prevention valve would have to be incorporated.
Really, you need to get with a local plumber who is well versed in the local codes and restrictions.
"Also, just as an FYI I think that sewage injection pumps are often connected to out-feed pipes of a smaller diameter than 3" - say 2.5"."Actually mine uses 1 1/2". But it is a force main system. The main is only 4" for about 150 homes.IIRC for basic sewer ejector pumps they use 2" lines.
the pump I have on the shelf is 1-1/2"...
can't remember where it came from but it's been the for some time..
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There may also be a problem connecting the new sewer line to the existing line unless it's already oversized.
Right - but a 4" line will service - whatever. When doing apartment construction, we had 4 units with 8 toilets, etc feeding into one 4". I was a little surprized but the plumber told me that a 4" line can handle a heck of a lot of sheet :-) Two 4" fed into a 6". an 8" services the whole apartment community. A rule of thumb someone told me one time - 3" line max 3 toilets. 4" line 4 or more toilets.
Here, in new single family construction it is always a 4" line going out to the street.
engineer spec'd a 4" line for my 20unit project... about 100 outlets ie showers, sinks washing machines ect...
I questioned it and it was explained to me.... high flow is good... with smaller pipe lots of stuff flow'n thru it HIGH FLOW ... vs large pipe and low flow... where you have the problem of liquids pass'n/leave'n the solid stuff behind....
worked for me since i had a 4" main come'n in anyway saved me about 10k
maybe a composting toilet and pump laundry shower sink s