How to Fix a Leaking Sink P-Trap in Denver, CO
In Denver's older bungalows and Denver Squares, the sink trap may still be chrome-plated brass or even connect to an original galvanized drain arm, and metal traps thin out and pit with age. Newer homes almost always have plastic traps that just need a reseal. Denver's soft-to-moderately-hard water leaves only light scale, so a drip usually comes from a worn washer, a cracked trap, or corrosion, not mineral buildup.
📺 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.
📍 Denver Tips for This Repair
- In pre-1960 Denver homes, check whether the trap is chrome-plated brass. If the metal is pitted or flakes when you squeeze it, replace the trap instead of re-tightening it.
- Denver lists like-for-like fixture replacement and general repairs that do not alter the plumbing as work that needs no building permit, so a trap repair in place qualifies.
- If the trap connects to an old galvanized drain arm in the wall, do not force it. A corroded arm can snap, which turns a small fix into a call to a plumber.
❓ Denver Repair FAQ
Do I need a permit to replace a sink trap in Denver?
No. Denver lists like-for-like fixture replacement and general repairs that do not alter the plumbing system among work that does not need a building permit.
Why does the old metal trap under my Denver sink keep leaking?
Chrome-plated brass traps in older homes thin out and corrode from the inside. A new plastic or brass trap usually fixes it for good.
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More Denver Repair Guides
Denver Housing Context
Denver's housing spans more than a century. About 16% of homes were built before 1940, including the brick bungalows and Denver Squares of older neighborhoods, and roughly a third date from before 1960. At the same time, about a quarter of the city's housing has been built since 2010. In the older homes, original drain lines, aging shut-off valves, and early electrical service are common. Freezing winter nights add the risk of frozen pipes in exterior walls and crawlspaces.
Denver Water Quality
Denver Water draws from mountain sources, including the upper South Platte and Blue rivers, Bear Creek, South Boulder Creek, and Fraser River tributaries, stored in reservoirs such as Dillon and Cheesman. The utility describes its water as soft to moderately hard. Its 2025 sampling averaged about 105 mg/L total hardness (roughly 6 grains per gallon), ranging from about 55 to 124 mg/L, with the northern system softer than the southern one. That means some mineral scale, but far less than in desert cities.
Municipal Permit & Code Guidance
Some plumbing and electrical work in Denver 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 Denver Community Planning and Development before starting.
For this repair in Denver: Denver lists replacing like-for-like plumbing fixtures, such as faucets and sinks, and general repairs that do not alter the plumbing system among work that needs no building permit. Re-sealing or replacing a trap in place fits that description.
Denver issues homeowner permits only to the legal owner who lives in a single-family home (not a condo, townhome, or duplex, and not a trust or LLC). The owner must do the work and pass a free homeowner exam before doing plumbing or electrical work.
Permit notes last reviewed October 2026 against official city and state pages. Rules change, so confirm before you start.
Visit Denver Community Planning and Development →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.