I am going through a major renovation in my house which involves excavating 7'6" basement and pouring seismically strong 15" slab as a floor.
The house is pretty high on the hill and something like 50' from the property line. I have a sewer line currently going under floor joists and in the middle of the space that will become a basement. So it will be above one's head after basement is done. In future, I want to consider getting a small powder room (toilet + sink) in that basement. So I decided that I want to reroute the sewer line under the slab using trenches excavated for drainage. Those trenches will be something like 6'-7' below the grade line.
Since we are on a small hill, per measurements, there should be enough slope for this sewer and lateral to be below the slab.
I will have plumber to do it but what are the things that I should look especially carefully considering that the entire house drain will go through this line and that fixing it may be ridiculously expensive?
Should I require specific access boxes installed at every join of the pipe? If so what is the recommended size and kind?
How should I evaluate the quality of all connections? I think pressure test is required anyway.
Best Answer
I'd suggest asking your plumber plenty of questions until you're comfortable with the way the installation is planned. If your plumber isn't a Q&A kind of plumber, feel free to hire a different one; some are personable and good with homeowners who like to be involved with their projects, and some aren't.
Including some clean-out fittings in your plan is a good idea. When I had a main sewer line replaced, I got one inside that was integrated with a back-flow preventer, one outside near the footing, and one installed where my service line met up with the city sewer connection. This cost maybe $100 more in materials & labor and allowed me to rule out any problems with the new line when troubleshooting a different problem just a few months later.
You don't need clean-outs at every turn or fitting in your under-slab sewer line, though you should consider having them installed everywhere a line comes up from the slab.
Consider getting a floor drain or two as well.
Also, while updating your drains, make sure whatever water heater tank(s) you have include catch-pans & drains.