Reroute of main sewage/waste water line to septic tank

[Destinmatt]

Our 1970's house was vacant for several years before we purchased a year ago. After we moved in we had numerous plumbing issues with the guest bathroom. After a LARGE sum of money, a national plumbing company in our area scoped the main waste line, put in a clean out and jetted the cast iron line clean. They then told us it had a long crack under the house (can't remember but 10-30ft long) and wanted $17k to fix it. We asked about some of the cheaper options with them (trenchless repair with a sleeve or pipe fracturing) and they dismissed these options. We told them to get lost and have gone without a hall bathroom since.

My question is, can we just bypass this main line for the bathroom and route it around the house? To our knowledge the Kitchen, HVAC drain, and hall bathroom are on the main septic line. Our clothes washer is presumably plumed to this line, but it was already diverted as grey water when we moved in. We have had no issue with the kitchen waste line and the HVAC drain has been fine since the line was jet cleaned. Even when the bathroom clogs, the kitchen/HVAC are fine.

Presumably to reroute we would need to plug/cap the waste line distal to where the sink/shower/toilet all meet. The toilet is against the exterior wall. We would somehow divert from there down below the footer or through the concrete footer (concrete slab foundation) and then trench around to the septic tank.

To sum up, is this possible? If so, is it ok to punch through the concrete footer to ensure proper slope for the waste pipe? How would I cap the cast iron pipe and would I likely need to demo the bathroom to do it? The sink drain line heads toward the toilet (exterior wall/not toward main line) Have no idea where the shower drains. As an added note, we are outside the city and have no permits/inspectors/HOA.

Brown= septic tanks (we have two)
Red lines= assumed course of current cast iron sewage line
Blue lines = proposed route of bypass line

[blackhat]

Your plan won't work. All the existing lines slope to flow in the direction they are installed. You would be asking water to flow uphill. Revisit the liner plan with other contractors.

[Destinmatt]

Ok, I just want to explore all options due to the drastic price difference from diy to professional. I don't quite understand how the slope of the existing pipe would be so significant that it would be impossible. I was kind of assuming the sink and shower went straight to the toilet drain, since it's the largest and that would be the start of the diversion.

[srv52761]

Your plan won't work. All the existing lines slope to flow in the direction they are installed. You would be asking water to flow uphill. Revisit the liner plan with other contractors.

Mmmm... I understand what you're saying. 
But I thought acceptable slope was anywhere from 1/4" to like 2" per foot.  If he is lucky they used something greater than 1/4" when they installed original.    For the price difference it may be worth his while to measure down the clean out, find  level, extend level through the house to the bathroom, multiply the alternate route by 1/4" and see how it compares. (remember to account for your first few inches of vertical DWV from the  toilet).  It only looks like about 8-10 feet more than original. 

And yes, I would expect your will have to remove the present floor.  Direction of joists could be a killer anyway.

Edit:  You do not say where you are located.  Doing this suggests you will be laying pipe relatively close to the surface when it first exits your building.  If you have to contend with freezing ground you may have to take heaving into account.

[Roly]

The problem is the end of the existing drain from the bathroom is the high point of the existing pipe.  The waste from the kitchen ,laundry and Hvac have to flow uphill to the high point to exit out the side.    Also the waste from the bathroom would want to flow down hill towards the kitchen.    Not good to have solid waste stuck in the pipe.   This is what Blackhat  is saying.  The elevation change of the new pipe would most likely work  but the existing under the floor is the problem.  Roly

[blackhat]

Exactly, if the OP followed his drawn plan, in 2 weeks, the only functional drains in that house would be the master bath "if" it all goes to that secondary tank on the right side of his sketch.

[Destinmatt]

My idea is to block the bathroom from the main line, not divert the whole line through the bathroom. For whatever reason the kitchen/HVAC is working fine. I assumed I could add a T connection to the septic inlet and call it a day. We are in Texas so it's a 100% concrete slab house with no ice heaving to worry about. Any pipe excavation in the house would be a jack hammer. The current waste line exits the footprint of the garage about 6 inches below the footer. I would assume that even with 1/8" slope for a 3-4" pipe I would need to chip into the footer for the slope.

[brianwelch]

Without getting mired in details, is an ejector pump something to consider? Maybe not the plan of choice, but possibly a viable solution...

[blackhat]

You would still need to break out much of the bathroom floor and repipe it. You would have to undercut the footing to achieve grade. You would still have a pipe leaking sewage under your floor. I don't see the attraction of that plan.

[tomsteve]

howz about getting an independent plumbing company or maybe even a plumber that does side jobs( maybe even a retired plumber that wants to earn some extra cash) in to take a look and see what they think and would charge?
national chain anything home repair are like auto dealership repairshops- want to suck every penny out of the owner for work that isn't necessary.