Rolling a 90-degree fitting allowed going from horizontal to diagonal?

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New Member
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I've done some googling and haven't been able to find an answer to this, so I apologize if this is covered elsewhere.

I have two pipes (one main trunk, and one toilet) that are both running in the horizontal plane, but perpendicular to each other and offset vertically (toilet line is above the main line). I need to bring the toilet down to merge with the trunk (so the toilet line needs to go horizontal to vertical, then back to horizontal again). This is all happening in a crawlspace.

If there was more vertical space between them, I would accomplish this by taking the toilet line dead vertical with a 90, then using a combo sweep or a Wye + 45 to enter the main line. However, all these fittings are a bit chunky at 3'', and I don't think I have the space.

I was considering starting off with a 90, but rolled 45 degrees, so the first transition would have a 45 degree slope down and to the right for a few inches, before entering a Wye-fitting on its back entering the main line. I couldn't find any articles that specifically disallowed this, but it seems funny enough I wanted to get confirmation either way. The main thing I see as unorthodox is that the drain line would have a (brief) section of steep (45 degree), but non-vertical slope, and I've read that drain lines shouldn't be "too steep", or the liquids might outrun the solids.

thanks for the tips!


In the Trades
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Berkeley, CA
Your proposed configuration is fine. 45 degrees from plumb is considered vertical, so the 90 that you use may be a quarter bend and doesn't need to be a LT90.

Cheers, Wayne
Hey, wait a minute.

This is awkward, but...

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