How to add a plumbing clean out to your main drain line

If your main drain backs up, you’ll know it. Sewage will start backing up at all of your plumbing fixtures; tubs, toilets, sinks, washer.

To fix this, you’ll need to break up the clog in your main drain. Often, you can find a plumbing clean out in your front yard. It’s usually a 3 or 4 inch pipe coming up at a 45 degree angle, with a threaded cap. This is where you insert the plumbing snake to clear the clog. Grease and tree roots are the most likely culprits.

You can also call the City’s Water and Sewer Dept., and they will probably come and snake it for you. They will here in Durham.

If you can’t find your clean out, you’ll have to dig. If you have a crawl space, locate the main drain under your house, and note where it exits at the front toward the street.

Find the corresponding spot in your yard, and draw an imaginary line to the street. If you have a clean out, it’s probably 10-15 feet from the curb. If you can see any of your neighbors’ clean outs in their yards, you can get an idea of distance from curb for yours.

If you dig and can’t find your clean out, you may need to install one.

Here’s how to install a plumbing clean out for your main drain:

1. Determine the diameter of your pipe, probably 4″.

2. Purchase parts, all the same diameter as your drain; A pvc “wye” fitting, a 45 degree “street” elbow, a female threaded adapter with plug, some additional pipe, and two “fernco” rubber fittings. The latter are rubber with hose clamps. If your main drain is pvc, you can get pvc repair couplings instead of ferncos. You’ll also need pvc primer and glue.

Fernco fitting

3. Break or cut your drain pipe so that you have room for the wye to fit. Cast iron can be broken with a mini sledge hammer, though getting an even break is tough. You can cut this pipe with a reciprocating saw if you have one,and a carbide blade. PVC is easy to cut with a reciprocating saw, or even a hand saw if you can clear enough space around it.

4. Glue short pieces of pvc pipe into the wye fitting, so that your wye assembly fits snugly into the space you’ve created by cutting the main drain.

5. Use the fernco fittings to put everything together. Loosen the hose clamps and slide the fittings over the pipe on both sides, set the wye assembly in place, slide the fittings over the joints, and tighten the hose clamps. If the main is pvc, you may be priming and gluing pvc rpair couplings for this step, instead of rubber ferncos.

6. Glue in the street 45 and a section of pvc pipe to the 45 degree leg of the wye, pointing up toward the yard. Use enough pipeto get you just above ground level, and attach your female threaded adapter with glue. Prime your glue joints first, and let the primer dry.

7. You now have a clean out. You can go to the tool rental shop and get a snake, and root out your clog, or call the City to do it. Bury the pipe, leaving the cap just above ground for future access. Hopefully you’ll never need it again :)

Here’s one I did recently, with pictures.

Wye fitting

Female threaded adapter


A long turn wye is an alternative to the standard wye plus street 45

About Mark Cool

Carpenter, Musician, Blogger, father of 2 great kids, Durham, NC.
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2 Responses to How to add a plumbing clean out to your main drain line

  1. Pingback: Plumbing drain issues- main drain clogged, toilet backing up into shower.

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