Toilet-Only Line

In our home we built, I separated the toilet blackwater line from all other greywater, which is allowed by our local codes.  I've done humanure composting for years, and the goal is to build a Flush Vermicomposting Toilet this coming Spring.  Should I be concerned about a toilet-only pipe run in terms of whether the solids will make it that far?

I used 3in plumbing for the toilet (same size as the toilet outlet).  The line goes about 8ft, then has one 45degree turn, then a 70ft run so far.  I have yet to connect the rest.  I'm hoping to keep the run <100ft with no more turns to avoid needing a cleanout as I hear they can hinder flow in blackwater lines.  I opted for the smaller 3in line allowed by code (vs 4in) because it should keep the water around the solids better, leading to more pressure.  We've purchased a low flow flush toilet, and there are 8-10 full time residents.  The line is run maybe a little on the high side of a 1/4in drop per foot (quarter bubble).

I am going to do the same thing for my cabin. Myself I am adding the bathroom sink to the same line. The most critical in the system is the slope of pipe for solids. The drop (slope) must be maintained to no less than 1/4" per 12 feet to 1/2" per 12 feet absolute maximum.  Less than this there is not enough water velocity to carry the solids, more than this the water goes around the solids and leaves them in place. Think of a raft floating gently down a stream.  Kitchen sinks add grease and bathtubs  induce too much water all at once agitating the system.

Although expensive, I wipe all my dishes clean with paper towel before I wash and throw them into the wood stove.

I don't know how well this applies to your situation as we can't separate our grey and black water waste here.  But it might help you see a potential problem to avoid.  

Should I be concerned about a toilet-only pipe run in terms of whether the solids will make it that far?

We had this problem when we first moved in.  We are low water users and the plumber said the solution was to reinstall the old toilets and take more baths.

The next plumber said the problem was the 70 year old cast iron pipe had sagged in the ground and made a rough/low spot for things to get clogged.  We had to dig that part of the pipe and rise it up, fill in the area with sand.  The plumber used his little robot to smooth the rough place on the pipe.  More than a decade later, it's not been an issue.

What is the overall advantage of what you are doing?
Are you creating more work than necessary with this project?
Is water conservation a high priority?

Bob Hutton wrote:no less than 1/4" per 12 feet to 1/2" per 12 feet absolute maximum.

Bob, the State permit says "minimum slope of 1⁄4 inch per foot (2%)", did you mean 1/4" per 12 inches to 1/2" per 12 inches?

Yes, my error.

Good to know an upper bound. Thank you!!!