Water appearing near a water heater can come from several different places, and the source matters. A dripping T&P valve, a weeping drain valve, and a leaking supply connection each mean something different. This guide covers each valve type, what a leak from each one indicates, and what to do about it, so you can act quickly.
Water coming from the bottom of the tank itself, rather than from a valve or connection, means tank failure. In that case, see our guide on water heater repair vs. replacement.
The Temperature and Pressure Relief Valve (T&P Valve)
The T&P valve is one of the most important safety components on a water heater. It opens automatically and releases water if the tank pressure or temperature exceeds safe limits. This prevents the tank from over-pressurizing to the point of rupture.
The T&P valve typically sits on the side of the tank near the top. A discharge pipe runs from it down toward the floor or a drain. It also has a lever handle that you can lift manually to test it.
A dripping T&P valve can mean two things:
1. The valve is doing its job
In this scenario, the tank is over-pressurizing or overheating. Maybe the temperature is set too high. Maybe supply pressure is pushing the tank above 150 PSI. Or the thermostat is malfunctioning and letting the water overheat. Whenever that happens, the T&P valve opens to relieve the pressure. In this case, the dripping is a symptom of an underlying problem. The valve itself is working, but you need to address the conditions causing it to open.
Signs this is the cause: the valve drips during or after heating cycles, and the discharge water is very hot. The heater may sit above 120°F. You may also notice high water pressure elsewhere — faucets that splash hard, pipes that knock.
What to do: Turn the water heater temperature down to 120°F. No pressure reducing valve (PRV) on your main supply, and home pressure above 80 PSI? A plumber should install one. Unregulated high pressure stresses every component in the plumbing system, not just the water heater. A thermal expansion tank installed on the cold water supply line to the water heater also helps manage pressure spikes.
2. The valve itself is faulty
T&P valves have a limited lifespan and can fail in two directions. They can stick open and drip with no actual over-pressure condition. Or they can fail to open when pressure rises — a safety concern rather than a visible leak issue. Does the valve drip consistently regardless of heating cycles, even with correct temperature and normal supply pressure? Then it’s likely worn and needs replacement.
T&P valve replacement is a straightforward repair. First, the plumber shuts off the heater, closes the cold inlet, and drains several gallons to reduce pressure. Then they remove the old valve, wrap the threads with plumber’s tape, install the new one, and restore the system. In fact, a licensed plumber can do this in under an hour. Moreover, the part itself is inexpensive ($15–$40 for most residential models).
Never plug, cap, or disable a T&P valve. It’s a safety device. A water heater without a functioning T&P valve is a genuine hazard.
The discharge pipe: The T&P discharge pipe must terminate within 6 inches of the floor or a drain. Never cap it, never run it upward, and never thread the end into a drain fitting. The pipe needs to discharge freely. If yours terminates incorrectly, that’s a code violation worth correcting during valve service.
The Drain Valve
The drain valve sits at the very bottom of the tank. It looks similar to a hose bib and drains the tank during maintenance or replacement.
A dripping drain valve usually traces back to sediment or debris caught in the valve seat, preventing a complete seal. Otherwise, a valve seat worn after years of infrequent use is to blame. Drain valves that have never seen use commonly develop a slow drip the first time someone opens them. They then fail to fully reseat.
What to do: For a minor drip, attach a hose cap or garden hose end cap to the drain valve outlet. This creates back pressure that often stops the drip. However, if the valve drips continuously regardless, replacement is the right answer. The plastic drain valves on many water heaters are inexpensive and not worth repairing. A brass replacement valve is more durable and worth the minor cost upgrade.
Replacing a drain valve requires draining the tank. That involves shutting off the water heater and cold water supply, attaching a hose, and draining to a floor drain or outdoors. A plumber can do this as part of the annual maintenance flush.
The Cold Water Inlet and Hot Water Outlet Connections
The supply connections at the top of the tank are where the cold water enters and the hot water exits. They can develop drips at the threaded fittings, particularly on older units. The nipples — short pipe sections threaded into the tank — corrode over time.
Signs: Water appearing at the top of the tank, running down the side. The drip is usually visible at the threaded connection between the nipple and the fitting or pipe.
What to do: If the connection is simply loose, tightening it may stop the drip. However, a corroded nipple — very common in Santa Cruz’s coastal environment on older units — needs replacement. Corroded dielectric nipples are one of the most common sources of top-of-tank leaks on older water heaters. These insulators prevent galvanic corrosion between dissimilar metals at the connection.
Fortunately, a plumber can replace corroded nipples and connections. Is the unit 10 or more years old with corroded connections? Then it’s worth assessing whether the overall condition justifies the repair cost versus replacement.
The Pressure Reducing Valve (If Applicable)
Some water heater installations include a pressure reducing valve on the cold water supply line. These can develop leaks at the body, at connections, or through the internal components over time. A leaking PRV is a plumber’s repair. It involves the main water supply line and requires shutting off the main to the house.
Condensation vs. a Leak
Before diagnosing a valve leak, confirm the water is actually coming from the valve. Condensation on the outside of the unit can fool you. In warm or humid weather, cold water entering the tank can cause condensation on the outside of the tank body. It then drips to the floor and mimics a bottom leak. Condensation typically forms more uniformly on the tank surface and is more pronounced in warm weather.
To distinguish: dry the suspected leak area with a towel and watch closely for where moisture returns. Generally, condensation reappears as droplets on the tank surface. A valve leak reappears at the valve body or discharge pipe.
When to Call a Plumber
- T&P valve drips that persist after temperature and pressure corrections
- T&P valve replacement
- Drain valve replacement
- Corroded inlet/outlet connections or nipples
- Any leak on a unit more than 10 years old — get a professional assessment before deciding on repair vs. replacement
- Any situation involving the gas supply, electrical connections, or the tank itself
Eco-Flow Plumbing Inc. handles water heater repair and installation throughout Santa Cruz County. Service areas include Santa Cruz, Live Oak, Aptos, Capitola, Soquel, Scotts Valley, Seabright, Felton, Boulder Creek, and Watsonville.
Contact Eco-Flow Plumbing to schedule service. Or call directly: (831) 818-6331.
