Building Homes or Extensions/Plumbing


How much slope can I have on a drain line from a bath room to the septic tank. Someone told me I could not have more than 2" every 4 ft. My problem is that there is approx. a 5ft. drop from the room to the septic tank. From the room to the tank is approx. 15ft.

Steep Slope Pipe Run
Steep Slope Pipe Run  

On the sloping portions of the pipe runs,  aim for 1/4" per foot of run.  This allows for proper clearing of solids.  

In your case, install a vertical drop early in the run, then finish out with a properly sloped run.  Really not much different than how a second floor toilet is piped. See attached diagram.

Bet of luck,
Steve Major  

Building Homes or Extensions

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Stephen Major (Owner--Major Design Group)


I can answer any questions regarding the design and construction of homes and additions. This includes trade-specific questions (how-to) in all major building trades: framing, foundations, site prep, electrical, HVAC, plumbing, water treatment, interior finishing, trim & cabinetwork, exterior finishing, roofing, siding. PLEASE indicate your state or region, so I can provide the best possible answer. PLEASE provide photos whenever possible.


30 years experience in building design and construction, all hands-on, including the construction of dozens of single-family homes and hundreds of remodeling projects in the northeastern US.

Author: "Architectural Woodwork - Details for Construction" published by Van Nostrand Reinhold (now Wiley).

BS Cornell University.

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