How to Fix a Leaking Sink P-Trap in Portland, OR
In Portland's older Craftsman and Bungalow homes — many built between the 1920s and 1970s — the sink P-trap fitting is often still original galvanized steel or an early plastic replacement that has grown brittle over decades of exposure to Bull Run's naturally soft water. Soft water is gentler on skin, but it's still mildly corrosive to aging metal fittings, which is why a slow drip under the kitchen sink is such a common Portland repair call.
📺 Video Tutorial: https://youtu.be/agasVgr0cjM
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📋 Step-by-Step Manual
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Step 1: Shut off the water and clear the cabinet
Turn off the shutoff valves under the sink (or the main water valve if there are none). Clear everything out from under the sink and place a bucket directly under the P-trap.
💡 Tip: Take a photo of the trap assembly before you touch anything — it makes reassembly much easier. -
Step 2: Loosen the slip nuts
By hand (or with pliers if they're stuck), turn the slip nuts on both ends of the P-trap counter-clockwise to loosen them.
⚠️ Caution: Keep the bucket in place — water trapped inside the pipe spills out as soon as the nuts loosen. -
Step 3: Remove the trap and inspect it
Slide the trap down and off the pipes. Check the rubber washers inside each slip nut — cracked, flattened, or hardened washers are almost always the cause of the leak.
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Step 4: Clean the pipe threads
Wipe down the threaded ends of the tailpiece and drain pipe. Remove any old tape, debris, or mineral buildup so the new washers can seat properly.
💡 Tip: Wrap PTFE tape clockwise around any threaded (not slip-joint) connections for extra insurance against leaks. -
Step 5: Install new washers and reassemble
Place the new rubber washers into the slip nuts with the beveled side facing the pipe. Slide the trap back into position and hand-tighten the slip nuts.
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Step 6: Snug the nuts and test for leaks
Turn the nuts an additional quarter-turn with pliers — don't overtighten, plastic nuts crack easily. Turn the water back on, run the faucet, and check every joint for drips.
💡 Tip: Dry the pipes with a paper towel and run water again after a few minutes — a slow leak is easier to spot on dry pipe.
📍 Portland Tips for This Repair
- Portland's permit rules treat repair of existing fixtures and their parts differently from installing new fixtures. Tightening or replacing parts of an existing trap is maintenance, while new fixtures with concealed plumbing connections may need a plumbing permit. Check with the Bureau of Development Services (BDS) if you are unsure.
- Bull Run water is soft and treated to raise pH, so mineral buildup is a less likely cause of a drip at a slip-nut joint. Check the washer and the trap alignment first.
- Portland homes built between the 1920s and 1970s sometimes still have galvanized supply piping. If you see heavy corrosion or flaking at the shut-off valve under the sink, stop and call a plumber instead of forcing the fitting.
❓ Portland Repair FAQ
Do I need a permit to replace a sink trap in Portland?
Portland's permit rules treat fixing or maintaining existing fixtures and their parts separately from installing or replacing fixtures. A like-for-like trap repair is on the maintenance side, but confirm with the Bureau of Development Services if concealed connections are involved.
Is Portland's water hard enough to damage plumbing fixtures?
No. Bull Run water is soft, and the Portland Water Bureau treats it to raise pH and reduce corrosion. Mineral scale is less of a concern here than in hard-water cities, though decades-old piping can still wear.
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More Portland Repair Guides
Portland Housing Context
Much of Portland's housing stock is 1920s-1970s Craftsman and Bungalow-style homes, many still running on original galvanized steel supply piping and early-generation electrical panels. Decades of internal corrosion in that piping is a leading cause of low water pressure and pinhole leaks, and the region's damp, poorly-vented crawlspaces are a common source of moisture and mold around plumbing fixtures.
Portland Water Quality
Portland draws its water from the Bull Run watershed, one of the softest municipal water supplies in the country. Soft water is gentle on skin and appliances, and it is naturally somewhat corrosive to metal piping. The Portland Water Bureau adds treatment to raise pH and reduce that effect, but decades of exposure can still contribute to internal wear in older galvanized and copper plumbing found in the city's pre-1970s homes.
Municipal Permit & Code Guidance
Some plumbing and electrical work in Portland may require a permit or inspection under local building code, especially anything involving new supply lines, panel upgrades, or moving fixtures. The steps below cover minor, homeowner-performed maintenance only — for any work that may require a permit, contact the Portland Bureau of Development Services (BDS) before starting.
For this repair in Portland: Repairing or tightening parts of an existing sink trap is maintenance. Portland's rules treat repair of existing fixtures and parts differently from installing new fixtures, which can need a plumbing permit, especially when concealed plumbing connections are involved.
Portland lets homeowners do their own plumbing work on the home they live in, but the homeowner must be the recorded property owner (not an LLC).
Permit notes last reviewed October 2026 against official city and state pages. Rules change, so confirm before you start.
Visit Portland Bureau of Development Services (BDS) →FixOrPro AI is not a substitute for local code review. Always verify permit requirements with your local building department before performing electrical, plumbing, or structural work.