Why is My Hot Water Tank Pressure Relief Valve Leaking and What to Do?
Finding a small pool of water on the floor near your hot water heater is never a welcome sight. Even worse is noticing that water seems to be dripping from the pressure relief valve at the top of your tank. A leaky pressure relief valve can be a nuisance, increase your energy bills, and in severe cases cause water damage if left unaddressed. But what causes these valves to leak in the first place? And what steps should you take to stop a leaking pressure relief valve on your hot water heater?
With some basic plumbing DIY skills and the right approach, you can likely fix a leaking pressure relief valve yourself without the need to call a plumber.
What is a Hot Water Tank Pressure Relief Valve?
First, let's make sure we understand what exactly is a pressure relief valve on a hot water heater. Also known as a T&P (temperature and pressure) relief valve, this device is a safety component of all residential water heaters. The valve is normally closed, but is designed to automatically open if either the temperature or pressure in the tank exceeds safe levels.
Definition and Purpose of a Pressure Relief Valve
When water inside the tank heats up, it naturally expands, increasing the pressure. The pressure relief valve serves as a safety release point when the pressure gets dangerously high. Most are set to open at 150 PSI. By releasing excess pressure, it protects the tank from rupture or explosion. The valves are mandatory on all water heaters for this critical safety purpose.
Where is the Pressure Relief Valve Located on a Hot Water Heater?
On most standard tank water heaters, the pressure relief valve is located near the top. It is connected to a discharge pipe that runs down the side of the tank to drain away any released water from the valve. The valves have a lever or knob on top to manually test and open the valve if needed.
How a Pressure Relief Valve Works
The valve contains a disc that is pressed against an opening by a calibrated spring. When pressure gets high enough inside the tank, the force presses the disc away from the opening against the spring tension, allowing hot water to escape through the valve and out the discharge pipe. This releases just enough pressure to bring the tank back down to a safe level. The spring then pushes the disc back into the closed position.
What Causes a Pressure Relief Valve to Leak?
Pressure relief valves don't normally leak or drip unless something is causing excess pressure in the tank. There are two main issues that can lead to leaking from a relief valve:
Excessive Pressure Buildup in the Tank
If the pressure inside the tank climbs too high, it will trigger the valve to open and release water as it is designed to do. However, the valve should then close tightly once pressure is reduced. If you experience persistent dripping, then the pressure is remaining too high and forcing the valve to stay open.
Thermal Expansion Causing Increased Tank Pressure
One phenomenon that contributes to elevated tank pressure is called thermal expansion. As the water heats up, it naturally expands in volume. In a closed system, like the hot water tank with no place for that expanded water to go, the pressure builds. This added pressure can be too much for the tank and plumbing system to handle.
Faulty Pressure Regulator Resulting in High Pressure
Excessive incoming water pressure from the municipal water supply system can overload the tank. Most homes have a pressure regulator that keeps the house water pressure in a safe 40-80 PSI range. If this device starts to fail, pressure could increase up to 120+ PSI and leak out the relief valve.
Worn Out or Faulty Pressure Relief Valve
Even when pressure levels are normal, the relief valve itself can develop issues and begin to leak. Common problems include:
Valve Failing to Close Completely
The spring that pushes the valve disc closed can weaken over time and no longer seal tightly. This allows water to leak through the slightly open valve.
Mineral Deposits or Sediment Preventing Proper Sealing
Hard water mineral buildup on the valve seat or disc can prevent full closure and create small leaks. Sediment stirred up from the tank can also interfere with the valve's seal.
Signs Your Pressure Relief Valve is Leaking
How do you know for sure if you have a dripping or leaking pressure relief valve? Here are some of the most common signs:
Dripping or Small Leak from the Valve
The most obvious sign is water actually leaking from the valve itself. You may see drops falling from the valve or running down the discharge pipe attached to it. The floor around the water heater may be wet.
Increased Water Bills from Leaked Water
A leaking valve can waste hundreds of gallons per month as hot water continually trickles out. This can drive up your family's water and energy usage significantly.
Reduced Hot Water Pressure
Pressure loss from the small leak can make your hot water pressure weaker in faucets and showers throughout the house.
Water Puddling Around the Hot Water Heater
Look for a puddle of water on the floor near the water heater. If the valve leak is slow it can take a while for the puddle to form. Check for moisture under the tank too.
Dangers and Problems of a Leaking Pressure Relief Valve
While a small leak may seem minor, there are good reasons to address a dripping pressure relief valve promptly. Some potential dangers and downsides include:
Risk of Water Damage from Leaks
Over time, leaking water can soak and warp flooring, damage drywall, and create mold risks. The leaked water is hot, making damage more likely.
Energy Wasted from Leaked Hot Water
All the hot water dripping from the valve around the clock can significantly increase your energy costs to heat the water. Hundreds of gallons per month could be lost.
Mineral Deposit Buildup
Water released from the leaking valve can leave behind calcium and mineral deposits on surfaces around the tank. This looks unsightly but can also lead to corrosion issues.
Increased Risk of Tank Corrosion and Rust
The constant moisture near the tank has the potential to cause premature rusting and corrosion, shortening your water heater's overall life.
How to Diagnose the Cause of a Leaking Pressure Relief Valve
Before attempting to fix a leaking pressure relief valve, it's important to properly diagnose why it is leaking in the first place. Follow these troubleshooting steps:
Inspecting the Valve and Checking for Obstructions
Remove the discharge pipe and examine the valve port and seat for any visible debris, mineral deposits or damage that could interfere with sealing. Make sure the lifting lever works freely without obstructions.
Testing the Tank Pressure with a Gauge
Use a water pressure gauge to measure the pressure inside the tank. Attach the gauge to the drain valve and open the valve briefly to record the pressure. If it is above 80 PSI, excess pressure is likely causing the leaks.
Ruling Out a Faulty Valve by Replacing It
Swap in a brand new relief valve that is properly rated for your tank. If the new valve still leaks, it clearly indicates an underlying pressure issue rather than a bad valve.
Fixing a Leaking Pressure Relief Valve
Once you've diagnosed the cause, choose the appropriate fix to stop the leakage for good:
Replacing a Faulty Pressure Relief Valve
If the valve itself is worn out or defective, replace it with an identical new valve with the same pressure rating capacity. Install it correctly with pipe dope and ensure the discharge pipe is flowing downward.
Installing an Expansion Tank for Thermal Expansion Issues
Connect an expansion tank to the cold water supply line. This provides space for the expanded hot water inside the tank to go, reducing pressure buildup. Make sure the expansion tank's capacity meets the water heater's BTU heating capacity.
Adjusting Pressure Regulator Settings
If the house water pressure is too high, a plumber can adjust your pressure regulator's setting down to 50-65 PSI. Lower pressure may fix leaks caused by pressure exceeding the valve's capacity.
Flushing the Tank and Valve of Mineral Deposits
Drain the tank and use a de-liming agent to break up any calcified mineral deposits or sediment inside the tank and valve that can prevent proper sealing. Flushing the tank and valve can help reduce small leaks.
When to Call a Professional Plumber about a Leaky Valve
Repairing a leaking pressure relief valve is a project many DIYers can tackle themselves. But in some cases, it pays to call in a professional plumber:
If Tank Pressure is Too High and Requires Adjustment
A plumber can diagnose the source of excess tank pressure and make adjustments to your home's plumbing accordingly to fix it.
When the Cause of the Leak Cannot Be Diagnosed
With experience and the right tools, plumbers can pinpoint why a relief valve is leaking in cases that leave DIYers stumped.
For Help Replacing a Faulty Valve
A plumber can ensure the new relief valve is installed correctly so that any leaks are fixed permanently.
FAQs about Pressure Relief Valve Leaks
What PSI should my hot water tank be set at?
The pressure of a residential water heater should be set between 50-80 PSI. Exceeding 80 PSI can cause the pressure relief valve to leak.
Where does the water go when the pressure relief valve opens?
A discharge pipe connects to the pressure relief valve and runs down alongside the hot water tank to drain away any released water from the valve.
Can I replace a pressure relief valve myself?
Yes, a faulty pressure relief valve can be replaced DIY-style with proper precautions. Make sure to get a valve with the same pressure rating as the original.
Is it normal for the pressure relief valve to leak a little bit?
No, the pressure relief valve should not leak at all if working properly. Any dripping or leakage indicates a problem needing repair.
Dealing with a leaky pressure relief valve on your hot water heater? First, take steps to diagnose the root cause, whether it is high tank pressure, thermal expansion, or a faulty valve. Then address the specific issue at hand. Replacing a worn-out pressure relief valve yourself is usually a straightforward fix. For ongoing elevated pressure problems, installing an expansion tank or adjusting your home's water pressure regulator are longer-term solutions. While a bit annoying, a dripping pressure relief valve is thankfully an affordable and manageable issue you can likely resolve yourself.