Water Still Flowing From Under Sink? Troubleshoot Your Plumbing
If you've ever shut off the water valve under your kitchen sink, only to find water still trickling out the faucet, you're not alone. This frustrating plumbing problem has stumped many DIYers. But with some diligent troubleshooting, you can get to the bottom of what's causing the water to defy the shutoff valve and continue flowing.
With the right diagnostics and repairs, you can finally stop the water from running out when the valve is closed.
Inspect Faucet and Pipes for Any Visible Leaks
The first thing to check is if there are any obvious leaks around the faucet or supply pipes under the sink. Even a small drip can allow water to bypass the shutoff valve. Examine all the connection points and spots where the pipes meet the faucet closely. Look for drips, moisture, or lime and rust deposits that could indicate a leak.
Tighten any loose pipe connections with an adjustable wrench. If you spot leaking parts like worn out washers or gaskets, replace them. Badly corroded sections of pipe should also be swapped out. Taking care of identifiable leaks could be an easy fix to the problem.
Check These Key Areas for Leaks:
- Where supply pipes connect to shutoff valves
- Pipe joints and elbow fittings
- Base of the faucet near supply lines
- Any corrosion or moisture on pipes
Clean Out Any Mineral Deposit Buildup
If your pipes and valves look leak-free, consider mineral buildup as the culprit. Years of flowing water leave behind calcium, magnesium, and other mineral deposits. This hard water buildup can prevent valves from fully closing and allow water to seep through.
Run some distilled vinegar through your pipes to dissolve any stubborn deposits. The acetic acid in vinegar will eat through built-up scale. For larger pipes, use up to a gallon of vinegar left to work overnight. Flush with water after to wash away loosened deposits. Your valves may work properly after being freed of mineral buildup.
Signs You Have Excessive Buildup:
- Reduced water flow
- White/gray scale around faucets
- Stains and mineral spots on fixtures
A water softener system or more frequent faucet aerator cleaning can prevent future buildup issues.
Replace Any Corroded Valves, Pipes, and Fittings
Galvanized steel pipes and old brass valves under the sink corrode over time. This corrosion can prevent proper water shutoff. Check for signs of corrosion like green deposits, flaky rust, or swollen plastic parts. If corrosion is extensive, replacement is likely needed.
Swapping out a corroded main shutoff valve should take priority. Replace galvanized supply pipes with new copper. Use plastic pipe for drain lines. Take the opportunity to update old, corroded pipe elbows, tees, and transition fittings. Your plumbing will function like new again.
Symptoms of Corrosion:
- Rust buildup inside valves
- Green copper corrosion
- Swollen/brittle plastic fittings
Verify Proper Water Pressure Regulation
Excess water pressure can also impede your shutoff valve's ability to fully close. Locate the pressure regulator valve on your main supply line. This is usually found near the home's main water shutoff valve.
Use a pressure gauge to check your home's static water pressure. It should fall in a safe 40-60 PSI range. If your pressure is too high, adjust the pressure regulator to reduce it to a normal range.
If your regulator valve is faulty, replace it with a new self-adjusting model. Installing an expansion tank will also help regulate pressure fluctuations.
How to Adjust Your Pressure Regulator:
- Locate regulator on main home supply line
- Check pressure using gauge
- Turn adjustment screw clockwise to reduce pressure
- Recheck pressure until in 40-60 PSI range
Make Sure Shutoff Valve Under Sink is Fully Closed
Before you assume the worst, double check that the shutoff valve under the sink is fully closed. Shutoff valves can become stuck over time due to mineral deposits or corrosion.
Turn the valve handle clockwise as far as it will go. Try closing it firmly several times to make sure it's properly engaged. If the valve feels stuck, spraying lubricant on the stem can help loosen it up.
Examine the valve interior for any damage. If the valve is defective, replacing it with a new 1/4 turn shutoff valve is the solution. Newer ball or gate designs offer smooth, reliable water shutoff.
Signs of a Malfunctioning Shutoff Valve:
- Handle spins freely without closing
- Water continues after multiple closure attempts
- Valve interior damage visible
Inspect Faucet Cartridge and Replace if Worn
The faucet cartridge controls water flow and mixing within your faucet. Over time, small holes, tears, and general wear prevent the cartridge from fully shutting water off.
If you notice leaks, difficulty shutting water off, or reduced water pressure at your faucet, the cartridge likely needs replacing. Locate the make and model of your faucet to order the right replacement cartridge. Installation is quick once you have the new part.
Signs Your Cartridge is Failing:
- Dripping water from spout when off
- Must wiggle handle to shut water off
- Decreased water flow and pressure
Check Water Meter to Detect Leaks Beyond the Sink
If you've addressed all potential issues under the sink, yet water still flows, look to problems beyond the shutoff valve. A running toilet, leaking pipe, or malfunctioning appliance could be the true culprit.
Check your water meter to see if it continues spinning despite having all fixtures and valves shut off. This indicates a leak is allowing water to flow somewhere.
Inspect all other household plumbing for leaks. Hire a plumber to pressure test your pipes to isolate the leak location. Repair any issues to finally stop the unnecessary water loss.
What a Running Meter Likely Means:
- Leak is allowing water use somewhere
- Specific leak location unknown
- Thorough inspection of all plumbing needed
Determine if Pipes are Frozen
In cold weather climates, frozen pipes are another possibility for why water flows with the valve closed. The expanding ice puts pressure on pipes, causing cracks and bursting. Frozen pipes continue allowing water to seep through.
Check for frozen areas on exposed pipes, especially near outer walls or uninsulated ceilings. Apply indirect heating using heat tape, heating pads, or a hair dryer to thaw ice blockages. Make sure to properly insulate vulnerable pipes before the next freeze.
Common Signs of Frozen Pipes:
- Visible ice or frost on pipes
- Frigid cold pipes to the touch
- Higher than normal water pressure
If you've made your way through all the above troubleshooting tips with no resolution, it's time to call a professional plumber. A licensed plumber has the expertise and tools to accurately diagnose why water is still flowing from under the sink when shut off.
They can pinpoint leak locations you can't access, replace worn parts, and ensure all repairs are water-tight. Plus, they can identify and fix any underlying issues that may be causing the problem in the first place.
While frustrating, persevering and finding the root cause of water flowing with the valve closed means you can finally stop needlessly wasting water and money on your bill.