Does new plumbing waste line have to be underground?

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Does new plumbing waste line have to be underground?

Post by SJPSF » Sun Aug 19, 2018 8:58 am

Hi all - we are about to start a project where we are converting our detached garage into a mother-in-law unit and adding a new bathroom with a shower, sink and toilet in it. The new bathroom will need to connect to the main sewer line and have a waste line/drain line (not sure what the right terminology is here sorry - I'm talking about the new pipe line that connects the new toilet to the main sewer line). The question is does this new line that will connect to the main sewer line have to be buried underground? We have gotten conflicting information from two plumbers: one said no it can just run under our deck as long as it has the right slope and it's not exposed to the sun; the other said it had to be underground and we would have to dig a trench. We live in San Diego so no frost worries here. It would cost a lot more to have to put it underground so just wondering if anyone knows if there is a code requirement that says it has to go underground? We can easily hide it under our deck to keep it away from sun exposure. Thank you!

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A. Spruce
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Re: Does new plumbing waste line have to be underground?

Post by A. Spruce » Sun Aug 19, 2018 9:58 am

I don't know what the code is, my suspicion is that is simple can't be "unprotected". If you live in a house that is on a raised foundation, ALL of the drain line is exposed until it exits the foundation, then it goes under ground. By being under the house, it is protected from being disturbed or damaged. I think similarly, by being under your deck it will have the same type of protection, so I would say that having it expose under the deck would be ok.

The only way to know for sure is to contact your local building department and ask them, as they will be the ones doing the inspection. Regulations change from jurisdiction to jurisdiction, so what works in one place doesn't always work in another, even though everyone works from the same base code book, local municipalities can augment their own requirements based on the general code.
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Re: Does new plumbing waste line have to be underground?

Post by Shannon » Sun Aug 19, 2018 5:54 pm

I’m thinking the same as Spruce but like he said your local office will know for sure.
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