Easy Plumbing 101: Why Water Heaters Leak and How to Fix Them

Water heaters commonly leak because of a damaged heat-out pipe or a faulty drain valve installation. It’s not unlikely for the thermostat to give away as well.

Too much water pressure is one of the main reasons why water heaters leak. If the pressure inside your water heater tank exceeds the 120psi margin, it can cause leakages in the glass lining.

Similarly, a thermostat set at the highest temperature gives rise to excess water vapor- putting undue pressure on the valve joints.

A 120°F thermostat reading is ideal for slowing down any sediment build-up which is another common cause of leakage.

Read on to know all the causes and solutions of water heater leaks.

Table of Contents

Leaking Water Heater: What Are the Causes?

A good water heater costs somewhere between six hundred dollars to a thousand bucks. When serviced regularly, your hot water tank can last a decade and more.

However, sometimes these tanks malfunction- serving up a cold water bath in mid-December. Don’t worry! Repairing the water heater is pretty easy. But first, you need to find out why it’s leaking, and where it’s leaking from.

Excess Pressure

As the water inside the tank heats up, the steamy water puts pressure on the tank’s interior walls. Some amount of pressure gets released through the heat-out pipes where your bath and kitchen outlets are connected.

But if you’re not using up the hot water, it stays in the reservoir and cannot release the pressure. What happens next is that the extra pressure puts stress on the valves. These valves open at the top for supplying water to your outlets and at the bottom for drainage purposes.

Excess pressure can loosen these valves or damage the connection points- eventually causing your water heater to leak. However, setting the thermostat at high temperatures can create too much steam. It also creates an undue amount of pressure inside the water tank.

Irregularities in the Shut-Off Valve

Shut-Off Valve

The dip tube or the main water supply line is connected to your water heater. When water enters the heater at high speeds from the dip tube, it can cause leakage from the bottom valve.

Next up, there’s a shut-off valve that stops the water flow once the water is level with the liner. But here’s the thing- it’s a separate valve located outside the tank.

If the shut-off valve isn’t working properly, you can get a flooded basement. Irregularities in any valve will come out on timely plumbing inspections. Considering you haven’t had your water heater checked in a while, problems in the shut-off valve are quite common.

Loose Cold Water Inlet & Drain Valve

A loose drain valve is the most common reason why water heaters leak in the first place. Whether you have an electric or a gas heater, valves are the first place to check for leaks. Besides, serious leaks can stem from a faulty cold water inlet- in which case you’ll notice leaks from the top part of the water heater.

You might choose a gas-powered heater with excellent first-hour ratings (FHR), but the condensed steam alone is enough to test its T&P valve. On top of that, a leaky drain valve and a worn-out gasket can render your expensive water heater completely ineffective.

Lastly, if you’re unsure where the leak is coming from, have your in-wall plumbing checked by an expert.

Sediment Build-Up

Water heaters come with a steel jacket on the outside. The inner tank is a glass-lined construction, and oftentimes it’s where the leaks take place. Sediments from the dip tube water can rust the water inlet and outlet valves. But they can also accumulate at the bottom of the tank and damage the glass lining in the process.

If that’s the case, you might notice water-puddling around the floor. People who use gas water heaters usually go for a sediment trap to troubleshoot the problem.

Damaged Pressure-Relief Valve

Relief Valve

A regular water heater will hold about 60 gallons of water at a 70-psi pressure level. If you have a surplus of pressure inside the tank, the pressure-relief valve automatically activates and takes care of the issue. It’s a safety mechanism for all water heaters for preventing floods, leaks, and accidents.

Although excess pressure triggers the tank’s pressure-relief valve in a normal scenario, a damaged valve won’t activate in time.

Now, a faulty pressure regulator can cause the pressure inside the reservoir to rise to unsafe levels. Anything above the hundred PSI ceiling is pretty dangerous for a household water heater. If a problematic pressure-relief valve is a reason, sitting on it can lead to repairs worth hundreds of dollars.

Rusted Components

Apart from leaks, copper-colored water is another sign that your glass-lined tank is corroding from the inside. However, it can also be a damaged sacrificial anode rod- a water heater component that is specially designed to prevent rust. Either way, it decays the tank and causes small leaks.

Scales can buildup around the heating elements inside an electric water heater. It might not lead to leakages but causes overheating along with irritating noise, nonetheless.

How to Fix a Leaking Water Heater

How to Fix a Leaking Water Heater

Now that we know all the reasons behind a nasty water heater leak, it’s time we showed you how to fix it! Well, if you’re lucky, it’s a loose valve and needs nothing more than a simple wrench for repairs.

Depending on the severity of the leakage condition, you might need to install sediment traps, flush the tank and replace its glass-lining with a plastic one. For now, let’s find out how to fix a leaking hot water tank at home in the easiest way!

Inspect the Heat-Out Pipe and the Drain Valve

Your water storage tank can leak because of rusty valves and damaged O-rings. Replacing the O-rings is not only easy but also pretty inexpensive. If there’s a leak in the heat-out pipe, the water that comes out of your faucet at home won’t be as hot.

However, a leaky drain valve is a much more serious condition because it can flood your garden, driveway, and basement. Pick up your garden hose, wrench, pliers, and a roll of plumber’s tape before booking a professional inspection. You got this!

Turn off the Power and Water Supply

While servicing an electric water heater all by yourself, make sure that you keep the power turned off the entire time. Switch off the designated breaker from the main breaker box.

You should turn off the gas burner to prevent accidental ignition during the repairing process. The pilot knob should be in the pilot setting.

And finally, close the gas line valve for shutting off the gas supply. You’ll find it close to the water heater itself. Let the heater cool down before you drain the water into the garden.

It’s Time to Drain!

You’ll need a garden hose that fits the heater’s drain valve for this step. Running the hose to a floor drain is the best option. Make sure that you open both the drain valve and the temperature and pressure relief valve all the way for quick drainage.

The reason why we recommend opening the T&P valve is that it prevents unnecessary suction and promotes better water flow outside.

If your drain valve has a spindle, turn it with a flathead driver and you’re good to go!

Replace the Damaged Drain Valve

Damaged Drain Valve

A replacement drain valve is easy to come by. Check the model number on your water heater to find the perfect match.

Now, let’s get down to business. Remove the old drain valve by locking it inside an adjustable wrench and turning it in a counter-clockwise motion. A pair of channel-lock pliers and a pipe wrench also work.

Before you install the new drain valve, don’t forget to wrap its threads with a bit of plumber’s tape. It will secure the valve joint from leaks while lubricating it for easy disassembly in the future!

Tighten the new valve with a wrench in a clockwise position. Lastly, open the cold water supply valve and turn on the power!

Install a Sediment Trap

Sediment traps prevent the debris in the main water supply line from entering your natural gas water tank. Most water heaters do not come with sediment and suffer from overheating, rusting, and leaking in a short period of time.
First, disconnect the gas supply line from the nipple. Thread in the sediment trap on the nipple using a Teflon tape and a wrench. Make sure that the bottom portion is downstream of the gas supply. Hand-tighten the supply pipe on the top nipple and ignite the pilot on the water heater. It’s that easy!

Change the Thermostat

A faulty thermostat on your electric water heater can play out in two ways- overheating or underheating.

Nowadays most electric water heaters come with two heating elements and include a dedicated thermostat for each unit. The upper thermostat is usually not the same as the lower thermostat. But they are interchangeable on some models.

Remove both the cover bracket and the reinforcing bracket to reveal the thermostat. Test with a voltmeter to check whether the power is really off. Now, remove the thermostat wires from their screwed terminals. Remember their positions to prevent incorrect wiring later on.

Take the old thermostat carefully out of its retaining bracket and replace it with the new one. Make sure that the back of the new thermostat is pressed securely against the water tank. Otherwise, you might get inaccurate temperature readings. Set your thermostat at 120 degrees and put the cover panel back on.

Bottom Line

Now you know why water heaters leak! And if you’ve read our water heater troubleshooting guide, you can change the drain valve and thermostat like a pro!

Surviving the chilly months without a water heater is impossible. Unless you’re entertaining the old-school bucket bath idea, have your leaky water heater fixed right away! Best of luck!