Advice on routing new sewer pipe through garage

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I recently purchased a house built in the 1940s with some side sewer issues. Rather than digging in a couple spots at the back of the house to reline the problem segment and continue using the existing side sewer to the street, one bidder (which comes well recommended and reviewed) advised rerouting instead, cutting an 18 inch wide trench in the concrete floor from the main wastewater pipe in the unfinished basement out through the garage floor to the driveway, and then down to the sidewalk. This would give me new pipe down to the street (rather than continuing to use most of the existing 80 year old side sewer) and the same trench can be used for replacing my galvanized water line that enters through the garage (at half the price I've been quoted for a trenchless water line replacement). The quote for all this is less than I've been quoted by other companies that have proposed digging in the side yard and under rear addition to reline the troubled segment.

So my main question is: are there major downsides to cutting into my garage floor, laying the new pipe, and then filling back in with concrete? For reference, the garage and basement are at street level (or slightly above) and the house has two floors have that. No doubt there will be dust, but 95% of the indoor cutting will be in the garage, so not as worried about that particular aspect. More wondering how worried I should be about compromising my foundation in some way. Thanks for your insights!


The Plumbing Wizard
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Bothell, Washington
Cutting concrete slab doesn't affect the foundations.
They will be using a wet saw for the cut, and maybe just a little work with a jack hammer. Cutting with a wet saw means two nice clean cuts to pour the concrete back to.
Most new Seattle area homes I was plumbing in the 70's ran the drains out through the garage anyway and down the driveway.

The guy I hire to do my wet saw work, played flag football with me in Everett. Most of the guys on the team were from Ballard High. I was the Bellevue guy. Playing defensive back. I had casted my ankle that Summer, after running down Cascade Pass with a 50 pound pack on my back. Took off the cast after six weeks and started playing football. I liked to shut down my side of the field.

John Gayewski

In the Trades
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Redoing the pipe is by far the best way. It won't affect your foundation. Thr wall should be drilled and sleeved so thr pipe can pass right through.

You can also ask him to install a double clean out in a convenient spot for future service. That way no one will have to come into your house to fix an odd backup.
Hey, wait a minute.

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