How to Tie Into Existing Drain Line


Want to know how to tie into existing drain line, or other pipe line, to add a wye, tee, or straight section of pipe? This post is for you. Whether you’re connecting copper, cast iron, or plastic the principle is the same. Cut out a section of pipe, lay in the new pipe, and use couplers to seal the deal.

Step 1 – Cut Out Old Pipe

Worker cutting drain line with a reciprocating saw

Remove a section of the existing pipe to the exact the size of the pipe you want to add in. Here I’m cutting out a section of PVC drain pipe using a cordless reciprocating saw with a fine tooth blade.

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Step 2 – Insert Couplings

Man placing couplings over cut drain line.

Slide a coupling onto both sides of the remaining pipe. In this case I’m using 4 inch rubber couplings. You can also use glued PVC sleeves for a more permanent connection. The Fernco couplings used here are underground rated. These are a good option for this non pressurized gutter drain, but sewer line often requires a coupling with more banding. Check your local code.

Step 3 – Lay in New Pipe

Worker measuring and marking PVC pipe with marker.

Lay in the new pipe and mark a line on its end half the size of your coupling. Here I’m marking off 2 inches for my 4 inch coupling. Slide the couplings over the new pipe to your half way mark.

Step 4 – Tighten Couplings

Hand holding a coupling torque wrench

Use a torque wrench that slips at the required tightness to secure the couplings. Pictured above is Pasco’s 5/16” wrench that sets the torque to 60 inch-pounds.

Step 5 – Test for Leaks

Man inserting water hose into drain pipe.

Whenever you tie into an existing drain line like this gutter drain it’s a good idea to perform a water test to check for any leaks at the new connections.

Congratulations, you did it! 😎 For more information on how to tie into an existing drain line check out this video:


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