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How to Check for Leaks Under Sinks — Wilmington, Delaware

Complete checklist with climate-adjusted recommendations for Wilmington, Delaware

Overview

Look for moisture, water stains, or mold under kitchen and bathroom sinks. Catching a slow leak early prevents cabinet damage, mold growth, and costly water damage repairs.

DIY FriendlyEasy~20 min

Step-by-Step Guide

1

Clear everything from under the sink

Remove all cleaning supplies, sponges, bags, and storage items from beneath the sink. A cluttered cabinet hides leaks for months. Set everything aside and inspect the empty cabinet floor.

2

Look for visible signs of moisture

Inspect the cabinet floor, back wall, and sides for water stains, warped or swollen wood, peeling laminate, mold or mildew, or musty odors. Dark stains on particle board are a telltale sign of slow leaks.

3

Inspect the supply line connections

Check the hot and cold water supply valves and the flexible hoses that connect them to the faucet. Feel each connection with a dry finger — any moisture at all indicates a leak. Look for mineral deposits (white crusty buildup) around fittings.

4

Check the P-trap and drain connections

Examine the curved P-trap pipe and all drain connections below the sink. Look for drips, corrosion, or green/white mineral buildup at slip-joint nuts. Gently wiggle each connection — loose fittings are a common leak source.

5

Run water and watch for active leaks

Turn on the faucet and let water run for 2-3 minutes at full pressure. Place a dry paper towel under each connection point. Watch closely for any drips — some leaks only appear under pressure.

6

Test the sprayer hose (kitchen sinks)

If your kitchen sink has a pull-down or side-mounted sprayer, activate it and check the hose connection beneath the sink for drips. Sprayer hose connections are a frequently overlooked leak source.

7

Check the garbage disposal connections (if applicable)

Inspect the garbage disposal flange where it meets the sink basin, the discharge tube, and the dishwasher inlet connection. Run the disposal briefly while watching for leaks at all three points.

8

Tighten or replace leaking connections

For dripping slip-joint nuts: hand-tighten plus a quarter turn with pliers. For supply line leaks: turn off the valve, disconnect, apply new thread tape, and reconnect. Replace supply hoses if they are more than 10 years old or show any signs of cracking.

What You'll Need

Tools

  • - Flashlight
  • - Dry paper towels or tissue
  • - Adjustable pliers or channel-lock pliers
  • - Thread seal tape (Teflon tape)
  • - Bucket or towel

Materials

  • - Replacement supply hoses (if cracked or old)
  • - Thread seal tape (PTFE/Teflon)
  • - Plumber's putty (for drain flange resealing)

Cost Estimates

DIY Cost

$0–$15 (thread tape and replacement supply hoses)

Professional Cost

$100–$300 for leak repair depending on the source

Safety Tips

  • Always turn off the water supply valves under the sink before disconnecting any hoses or pipes.
  • Place a bucket or towel under connections before loosening them — residual water will drain out.
  • If you see black mold under the sink, wear a mask and gloves. Extensive mold may require professional remediation.

When to Call a Professional

Call a plumber if you find a corroded or cracked supply valve that you cannot turn off, if the P-trap or drain pipes are corroded through, if there is extensive mold or water damage to the cabinet or subfloor, or if a leak persists after tightening all connections.

Pro Tip

Check under every sink in your home once a month — just a quick 30-second flashlight glance. The average under-sink leak runs unnoticed for 6 months before being discovered, causing hundreds to thousands of dollars in hidden water damage.

Common Mistakes to Avoid

  • Storing too much under the sink — clutter hides leaks for months. Keep the area organized so you can spot moisture quickly.
  • Overtightening plastic slip-joint nuts which cracks the fittings and creates a worse leak.
  • Ignoring supply hose age — braided stainless steel supply hoses should be replaced every 8-10 years. Rubber hoses should be replaced every 5 years.
  • Only checking during dry conditions — run the water for a few minutes under full pressure to reveal leaks that only occur during use.

Local Plumbers in Wilmington

ProPortal
Mike Ferrell Plumbing

Mike Ferrell Plumbing

Dover, DE

(302) 399-8980
0
B Walls & Sons Inc

B Walls & Sons Inc

Dover, DE

(302) 856-4045
0

Dickson Plumbing

Dover, DE

(302) 535-9595
0
C&N Services

C&N Services

Dover, DE

(302) 538-9261
0

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Wilmington Housing Market

Median Home Price

$308,950

Homes for Sale

81

Price per Sq Ft

$210

Local Pros

655

Home Service Professionals Near Wilmington

Agents 173Landscapers 82multimedia_specialist 81lender 75Movers 71Roofers 61HVAC Techs 57Flooring 55

Median Household Income

$55,269

Median Home Value

$224,500

Median Rent

$1,187/mo

Homeownership Rate

46%

Population

71,124

Median Year Built

1946

Source: U.S. Census Bureau, ACS 2023 5-Year Estimates

Fair Market Rents — Wilmington

Studio

$1,397/mo

1 Bedroom

$1,520/mo

2 Bedroom

$1,810/mo

3 Bedroom

$2,170/mo

4 Bedroom

$2,423/mo

Source: HUD FY2026 Fair Market Rents — Philadelphia-Camden-Wilmington, PA-NJ-DE-MD MSA

Related How-To Guides

How to Check and Clean the AC Condensate Drain Line

Pour a cup of bleach or vinegar down the AC condensate drain to prevent algae clogs. A blocked drain line is the number-one cause of AC shutdowns and water damage.

How to Test Your Home's Water Pressure

Attach a pressure gauge to a hose bib. Normal is 40-60 PSI. Above 80 PSI can damage pipes, appliances, and fixtures — install a pressure-reducing valve if needed.

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