plumbing

name	plumbing
description	Use this skill when the user reports a leak, clogged drain, running toilet, low water pressure, or any pipe-related issue. Also triggers on 'my basement is flooding', 'the faucet won't stop dripping', or 'there's water coming from the ceiling'. Do NOT use for data leaks or memory leaks — see the cybersecurity and debugging skills instead.
license	Journeyman Plumber License required in most jurisdictions.
metadata	{"author":"joshrotenberg","version":"1.0","references":"IPC 2021 (International Plumbing Code), CDA Copper Tube Handbook, ASPE Plumbing Engineering Design Handbook"}

Plumbing — Leak Repair, Pipe Fitting, and Drain Clearing

Overview

A residential plumbing system consists of two independent networks: a pressurized supply system (40–80 psi) delivering hot and cold water to fixtures, and a gravity-fed drain-waste-vent (DWV) system carrying waste to the sewer or septic. Supply lines are typically 1/2" or 3/4" copper, PEX, or CPVC. Drain lines are 1-1/2" to 4" ABS or PVC, sloped at 1/4" per foot minimum. See references/PIPE-SIZING.md for pipe dimensions, fixture drain sizes, and pressure specifications.

Prerequisites

Ensure the following are within reach before beginning any repair:

• Adjustable wrench (10") and channel-lock pliers (12")
• Pipe wrench (14") for threaded connections
• Basin wrench for faucet supply nuts in tight spaces
• Tube cutter for copper; PEX crimper or expansion tool for PEX
• Teflon tape (yellow for gas, white for water) and pipe dope
• Bucket and towels. Always have a bucket and towels.
• Headlamp. Under-sink work requires both hands and the ability to see.

Leak Repair: Copper Supply Line

Step 1: Shut off the water

Locate the nearest shutoff valve upstream of the leak. For supply lines, this is usually a quarter-turn ball valve under the fixture or at the branch. Turn the handle perpendicular to the pipe. If no local shutoff exists, shut off the main at the meter or where the service line enters the building.

Open the faucet downstream to relieve pressure and drain the line.

Step 2: Assess the damage

Dry the area thoroughly and determine the source. Pinhole leaks in copper often appear as a green patina or mineral crust at the leak site. Joint leaks appear as water tracking along the pipe from a solder connection.

For a pinhole leak in a straight section, you will cut out the damaged segment and splice in new copper with couplings. For a failed solder joint, you will need to desolder, clean, and resolder.

Step 3: Cut out the damaged section

Mark your cuts at least 1" beyond the damaged area on each side. Use a tube cutter — place it around the pipe, tighten the cutting wheel until it contacts the copper, and rotate the cutter around the pipe, tightening 1/4 turn after each full rotation. Do not overtighten; this will deform the pipe and create a lip that prevents the fitting from seating.

Deburr the inside of both cut ends with the reamer attached to the tube cutter or a round file.

Step 4: Prepare the splice

You will need a short length of replacement copper pipe and two slip couplings (they have no internal stop, allowing you to slide them fully over the pipe to position them).

Clean the outside of both pipe ends and the inside of both couplings with emery cloth or a copper fitting brush. Clean copper should be uniformly bright and shiny. Apply a thin, even coat of flux (water-soluble, lead-free) to all mating surfaces.

Slide the couplings onto the existing pipe ends, position the replacement piece, and center the couplings over the joints.

Step 5: Solder the joints

Light a propane torch and adjust to a steady blue flame about 1" long. Heat the fitting — not the pipe — by directing the flame at the body of the coupling. The fitting needs to be hot enough that solder melts on contact with it, not because the flame is touching the solder.

Touch lead-free solder wire to the joint where the pipe meets the coupling. When the flux sizzles and the fitting is at temperature, the solder will be drawn into the joint by capillary action. Feed about 1/2" to 3/4" of solder per 1/2" joint. You will see a bright ring of solder appear around the circumference.

Remove the heat. Wipe the joint immediately with a damp rag to remove excess flux and smooth the solder. The joint should show a consistent fillet of solder all the way around with no gaps or voids.

Repeat for the remaining joints. Allow to cool for several minutes before turning the water back on.

Step 6: Test

Turn the shutoff valve back on slowly. Check each joint for leaks. Even a small weep means the joint must be drained, refluxed, and resoldered. A good joint will hold system pressure indefinitely.

Drain Clearing

Plunger

Use a flange plunger for toilets (the extended cup seats in the drain opening) and a cup plunger for sinks. Fill the fixture with enough water to cover the plunger cup. Place the plunger squarely over the drain, press down to seat it, then pump vigorously 15–20 times maintaining the seal. Pull sharply on the last stroke to break the clog free.

For double-basin kitchen sinks, plug the second drain with a wet rag before plunging.

Drain snake

Feed a 1/4" or 5/16" drain snake into the drain opening or the cleanout. Push until you feel resistance, then tighten the thumbscrew on the canister and rotate the snake clockwise while applying moderate forward pressure. When the resistance gives way, continue feeding another 12" past the clog, then retract slowly while continuing to rotate.

Run hot water for several minutes to flush the debris.

When to call a professional

If the clog recurs within a few weeks, or if multiple fixtures are backing up simultaneously, the blockage is in a main line and requires a powered drum auger or hydrojetting equipment. This is not a homeowner repair.

Common Mistakes

• Forgetting to drain the line before soldering. Water in the pipe will prevent the joint from reaching temperature. Even a slow drip is enough. Stuff a piece of white bread into the pipe upstream — it absorbs the residual water and dissolves when you restore flow.
• Overtightening compression fittings. They seal with a brass ferrule that deforms onto the pipe. A quarter turn past finger-tight is sufficient. If it leaks, tighten another quarter turn. Do not crank it.
• Using the wrong Teflon tape direction. Wrap clockwise as viewed from the threaded end, so the tape tightens as you thread the fitting on, not bunches up.
• Not supporting the pipe when tightening a fitting. Always use a backup wrench on the pipe or fitting you're tightening against. Otherwise you will stress a joint somewhere else in the line and create a new leak.