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Hot Water Heater Leaking from Top

Hot Water Heater Leaking from Top

If you’re seeing any signs of your hot water heater leaking from top to bottom you should definitely give it your attention.

Unexplained water sitting on top or below your water heater isn’t always a cause for great alarm; but it’s up to you to find out what’s going on.

When it comes to your water heating system, there are many places a water leak can come from, and there is always a reason for it.

Water can except from your tank and it’s many parts in seemingly mysterious ways.

The information in this article can help you solve the mystery and decide if the fix is something to do yourself, or if calling a plumber is in order.

Below is a comprehensive guide covering every place water can potentially leak from your water heater on the top.

We then look at what’s behind the leak occurring in the first place and then, most importantly, what you should do about it.

We then look at ways to maintain your water heater, and in essence, prevent problems with leaking as best we can.

And yes, we’ll even look at how hot water heaters explode – a tank rupture, which is the absolute worst kind of leak you can have in your house.

The most common types of water heater leaking from top issues are examined below. To get started, use these quick links to find your specific problem.

Why Is My Hot Water Heater Leaking from the Top?

Since water heater tanks are required to be elevated off the ground (and are tall to begin with), leaks in this location can be hard to notice right away.

It’s often after water begins to drip down the side of the tank that we spot the problem.

So, what’s up here anyway that might give way to a leak?

The three biggest culprits are the cold water inlet, hot water outlet, and on many models a temperature and pressure relief valve is located on top. 

Many times a loose or corroded connection can cause issues. If you suspect water is coming from one of these spots but not sure, it’s best to take a closer look. Grab a step stool and flash light to confirm your suspicions.

If you’re not convinced one of the above is the source of the leak, there are a couple other things to look it.

If you have a gas hot water heater leaking from the top, one possibility is related to rain. Rainwater can be blown in from outside.

That metal vent on top of your gas water heater extends through your house to your roof. Under the right conditions, rain drops can enter and come down the vent.

When it reaches the end, it’s not uncommon to find a small puddle on top of your water tank.

If it hasn’t rained in awhile or you have an electric hot water heater leaking on top, then carefully check the copper plumbing directly above your tank.

Sometimes, valves in these overhead pipes can begin to secrete water, and of course, gravity brings it down. Use a flashlight to run your finger or a thin tissue around any visible valve connections to detect moisture.

Condensation can occur in this area of your water tank. Of course your tank gives off heat (water is 210°F/100°C inside). But sometimes it gives off heat longer than it should.

This can happen when an undersized tank for your home’s size is being used and is getting called upon to produce hot water more often, with not much in reserve.

Depending on the relative humidity in your garage or basement, moisture can easily collect on this consistently warm, dry surface.

One other type of leak we can look at up on top is not related to water at all. It has to do with combustion material that may be spewing out of the vent opening where the CO damper is and collecting on the top face of your tank. If you see signs of this, read below.

Pressure Relief Valve Leaking

Sometimes a water heater leaks on purpose. A pressure relief valve (a.k.a. TP valve, T&P valve or TPR valve) can open to lower internal temperature and relieve water pressure (as its name implies). 

A TP valve is a water heater’s most important safety feature, and it’s the number one defense against a tank exploding should pressure from heat and water get too high internally.

How Does it Work?

A pressure relief valve is designed to open and release water if the temperature inside the tank exceeds 210°F/100°C (just below boiling point) OR if pressure in the tank exceeds 150psi (the max normal operating temp for water heater).

It’s made with a 3” wax stem on the internal side. As the wax heats up and expands, it pushes on a spring that when compressed, can open the valve.

Pressure control comes when water pressure from thermal expansion (hot water getting heated more and more) pushes directly on the spring to open up the relief valve.

Once the valve is open, any escaping water should be discharged down a vertical pipe directly connected to the relief valve.

Why Does a TP Relief Valve Leak?

While no water heater leaking from top area components is good, a hot water heater pressure relief valve leaking is usually more indicative of another underlying problem.

Here are the most common reasons you might find water dripping from this device or from out of the overflow pipe it’s attached to:

Thermal Expansion – Simply put, a relief valve leaks most often when it’s doing what it’s supposed to do: lower the pressure inside the tank.

When it leaks, it’s a sign that something in your overall system isn’t right, namely pressure inside your tank. This pressure comes in the form of expanding water due to increasing water temperatures inside your tank.

If the water in your tank is getting heated beyond the acceptable 210°F, it wants to turn into steam and evaporate.

In fact, when boiling water above this temperature is in contact with Earth’s atmosphere (our air!), it will expand at a rate of one cubic inch to one cubic foot in the blink of an eye.

So, if something in your system is causing your hot water to “super heat”, it’s going to seek a way out. Your relief valve will open (as it should), and attempt to offset the thermal expansion due to super heated, expanding water.

Excess Water Pressure – This is related to  water pressure that is supplying the tank. Think of a hose going into a bucket with a lid on top and only a small hole for water to exit.

The more you open up your hose spigot, the more water pressure in the bucket.

Corrosion – Over time, the spring inside the valve mechanism can rust or become embedded with minerals from contact with hard water. Solution: Replacement

Age – These valves are mechanical and made of multiple parts that work together. It’s just a matter of time for these components and materials to become weak just by doing their job.

The spring inside is usually the first to go, as over time it can weaken and start to give too easily, i.e. much less pressure than the 150psi it’s design to resist.

They will usually last as long as the water heater’s life expectancy (8-13 years), but checking their function yearly is the best way to monitor their integrity. Solution: Replacement

Not closed down enough – Ever find a dripping faucet in the bathroom that was easily fixed by turning the faucet handle all the way?

The same can happen if the relief valve isn’t pushed in and closed completely. These are hard to open and close on purpose, so it may take some muscle.

Of course, if your valve is older and has minerals clogging up the works, then you may not be able to close it all the way. This can happen if you open it to test, for example.

If it won’t close all the way, you could say it did NOT pass the test!

A note about thermal expansion and water supply:

As you probably know, the water intake feeding your water heater is attached to the main water line feeding your house from the outside.

Water is intended to come in one direction, to your water heater.

However, if your tank builds up enough pressure from thermal expansion then water can actually begin to flow the opposite direction as if the tank pressure wins out against the water main pressure.

This is actually fine, and is a valid way for your water heater to let off some steam so to speak.

That said, this is no longer a standard in today’s new construction. New homes and many dwelling and buildings in fact now have a plumbing code specified pressure regulator installed on the main water infeed line coming in.

It’s a good thing, as it downgrades water pressures from unwanted triple digits, say 120psi to a much healthier range of of <100psi.

Along with this regulating device comes a check valve; a backflow preventer mechanism that purposely stops water that’s entered the closed system of a home from re-entering the public potable water supply again.

In other words, the buck stops here as far as your water heating system relieving it’s excessive pressure back to the city water. What then?

What to Do?

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As we saw above, thermal expansion is what we usually need to look at for a dripping TP valve.

But you need to know what’s causing your TP valve to open –  extreme temperatures or water pressure? You can test to find this out with two tests. You’ll need a water pressure gauge to do these tests.

  1. Check if internal temperature is too high: Measuring the water pressure in your home’s plumbing gives you some good-to-know information.

    What plumbers do is attach a water pressure gauge to your water heater’s drain spout. While keeping all hot water from running in your house, turn up your water heater’s thermostat to kick-start it into heating up the water.

    Watch the pressure gauge. If it begins to move up then you have an issue with the water expanding too high due to heat.

    If this is the case, then you can try lowering your thermostat. Some homeowners mistakenly see “hot” on the thermostat dial and think this is what will give them hot water. In reality, it’s entering a dangerous level, as occupants can get scalded.

    If you’re worried about killing germs on dishes, remember that dishwashers these days come with their own heating elements to heat water to necessary levels to kill bacteria.

Thermal Expansion Tank
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Install thermal expansion tank: 

The best thing you can do if you have a consistent thermal expansion problem is install an external tank. 

You just don’t want to have to rely on your T&P valve to release the hot water building up in your tank. As many homeowners know, this can happen daily.

These tanks are relatively easy to install, and essentially absorb expanding water from your main tank to take the load off of it when needed. With this, your TP valve will stay closed under normal conditions.

Check if there’s too much water pressure: Similar to the above, you’ll use your water pressure gauge again. With it attached to your drain outlet, turn off your gas to cut out the burners (or unplug/turn off the breaker to your electric water heater).

Now, open a hot water faucet in the house somewhere and let it run. If pressure begins to rise, then your water supply “psi” is too high. i.e. your tank is refilling with water coming in at too high of a pressure.

The PSI you want to see on your gauge is around 80psi or less. The ideal range if 50-60psi. If you find your incoming pressure is in the high range then a water pressure regulator needs to be installed on the water inlet line coming from the street.

If neither of the above two checks lead to an increase in water pressure on your gauge then you know it’s probably time to just replace your relief valve.

As a final check, you can try to open and close it a few times to loosen any dirt or fine sediment that may be keeping it slightly open, but it’s still best to replace a leaking T&P valve.

If your water heater does overheat and your T & P valve is discharging water or steam, the ONLY safe intervention is to remove the heat source by cutting off its fuel, if you can.

For an electric heater, trip the circuit breaker; for a gas heater, shut off the gas.

Never Cap Off a Leaking Relief Valve on a Water Heater!

Probably the biggest safety tip of this entire article is that you should never attempt to plug up or cap off TP valve that is releasing water. Check your water heater regardless and make sure there is nothing plugging it up from a previous owner. This is the only way expanding water can escape from your tank, and as some would say, keep it from turning into a bomb.

How to Replace a Leaking Pressure Relief Valve

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To do this, first, shut off the electricity to the water heater (or shut off the gas valve if your is gas). Then turn off the water supply to the tank.

Now, you’ll need to drain water from the tank so that you can bring the water level down past the height of the pressure relief valve.

This could be a couple gallons if your pressure relief valve is at the to of your tank. If it’s on the side somewhere, then drain about 5 gallons. You’ll know if you open the valve and no water comes out!

Use a wrench to loosen the relief valve. If yours has a discharge pipe, that will twist off as well. When you replace the pressure relief valve, be sure to do so with the exact same type.

Use teflon tape over the threads of the pipe you’ll be screwing the new relief valve onto. After tightening, open the water supply valve, turn on the power or relight the pilot light (gas).

If your new valve still leaks, you may need to address the problem with your house’s water pressure regulator. Have a plumber come out to test the pressure on your main water line.

The regulator allows for thermal pressure. If it doesn’t, it may be causing undo pressure in your water heater relief valve and causing it to open, thus a recurrence of your hot water heater leaking issue.

Water Heater Leaking from Top Cold Water Inlet

Simply put, the cold water inlet is the connection for your water supply line to your water heater. A copper pipe connects to an inlet port via a nipple connector.

The nipple is plastic on the inside, with an outer liner made of galvanized steel.

The purpose of a plastic interior is to keep water from ever touching the outer fitting material, to ward of electrolysis, i.e. rust. On he lower end of this fitting, is a dip tube that gets threaded in and drops down into your water heater.

On the upper side is another threaded end, which receives a connector that will be joined to the water supply pipe.

Why Does a Water Leak From a Cold Water Inlet?

There are a couple reason water can leak from here. One characteristic of the connection here is that it’s a natural weak link within your water heater plumbing.

That means, if thermal expansion pushes hard enough, it will find a way out if the connection here wasn’t installed cleanly and solidly.

Unfortunately, if this fitting isn’t properly installed with Teflon tape and lubricated with pipe dope, then water damage can begin.

Corrosion here can weaken the connection over time as it dissolves the mismatched metals of copper and steel. This is the perfect lab for galvanic corrosion.

Further, if you have a water softener that gets charged with sodium or salt ions, it can actually help speed up this chemical reaction since sodium can play a key part in promoting this type of reaction between two different metals such as iron and aluminum.

What to Do?

In this case, the first thing to check is for any looseness of the pipe feeding down and the join/nipple connections.

Does it wobble in your hands with slight pressure?

Can you turn it at all if you twist it (most likely not as expansion and contraction from constant hot and cold water will lock this connection pretty well). If so, tighten with a pipe wrench.

Next, you can check visually for obvious signs of corrosion around the threaded connection points.

If you see anything other than squeaky clean surfaces where your water heater is leaking from topside pipes (other than some dust!), these connections need to be replaced.

If the connects all look good but you suspect condensation is to blame, then consider wrapping these pipes with standard pip insulation to keep humid air from contacting the colder pipes.

How to Replace a Cold Water Supply Connection

For the average homeowner, this usually requires a plumber. For a seasoned DIY’er who wants to save money it’s just a few steps.

Note, you made need to bring some muscle and have experience soldering copper piping.

You’ll also need a plumber’s pipe wrench, a new “F.I.P.” or dielectric heat trap nipple (like this one), Teflon tape, pipe dope, copper female adapter, and copper coupling.

If you want to join the copper pipes without soldering, then feel free to pick up a “shark bite” coupling. You might find that spending $5-10 is well worth  not having to hassle with blow torches and soldering wire.

  1. Turn off the water supply to your water heater
  2. Using a pipe cutting tool like this one for tight spaces, cut the water pipe a couple inches below the lowest soldered joint (clean with an emery cloth first)
  3. Drain your tank just slightly so you don’t get any overflow as you remove the parts your replacing, along with pulling out the dip tube
  4. Using a pipe wrench, grab onto the the steel connector using what’s called a “three corner bite” (teeth of wrench on two jaw sides and the back smooth jaw of the wrench). This will help hold in round and avoid deforming the malleable heat-saver nipple
  5. Turn counter-clockwise with a strong, controlled motion
  6. Once it budges, continue to rotate out with a pliers and then by hand
  7. Now you can examine what might have gone wrong with the connector; most likely the metal threading has rusted and broken down
  8. Use a copper female adapter and solder it FIRST to the short piece of the supply line you cut in Step 2 (you don’t want to solder after you twist it onto your new nipple because you don’t want to melt the plastic inside
  9. To install your replacement nipple, simply join it to the dip tube in the tank and then to the two pieces you made in Step 7. Be sure to use both Teflon tape and then pipe joint compound like Teflon paste, cover ALL of the threading first before twisting on. Tighten down with your wrench pretty good so your new connection doesn’t leak.
  10. Solder the coupling in place or use a water tight shark bite joiner on where you cut in Step 2
  11. Turn your water back on, and you’re ready to go!

Overflow Pipe Leaking

If you see your hot water heater leaking from the overflow pipe, it’s your pressure relief valve. See above, as all information is related to this part.

An overflow pipe or “discharge tube” is merely an extension of your TP valve so that any leaking water can run down this vertical pipe instead of spraying hot water out into the open.

Drain Valve Leaking

Sometimes a hot water leak can be due to a bad drain valve. These valves can either be metal or plastic types.

Metal types are called sillcock valves and have little washers, which may be replaced if leaking is occurring. Use a wrench to remove the sillcock valve and to put it back on.

Be sure to use teflon tape on the threads after you’ve replaced the sillcock washer and are ready to tighten the sillcock valve back on.

If your drain valve is plastic, then it needs to be replaced if it’s leaking water. To remove, use hand pressure only. Do this by turning the valve counterclockwise four full revolutions.

Stop, and then pull on the valve handle while turning the valve clockwise six full revolutions. The valve should release from the tank.

When you replace this valve, use the same type that was on there. When installing the new one, reverse what you did to get the old one off. Be sure to push during the first six counterclockwise revolutions.

Faucets Dripping Hot Water

Believe it or not there are situations where you might mistakenly blame your water heater for a leak else where in your house.

If you find hot water dripping out of your kitchen faucet or your bathrooms, rest assured it is the fault of your faucet. 

A water heater leaking from top floors in your house via the faucets can be hard to diagnose at first.

A hot water heater merely pushes the heated water through your pipes to your faucet. It’s the job of the control valve to hold back this water until you’re ready to turn it on.

If the hot side of the faucet is compromised in some way and letting water drip through, then it’s literally pulling hot water produced by your hot water heater. The best thing to do is fix the hot

The worst kind of hot water heater leak is the one that doesn’t fit the descriptions of any of the above.

Sorry, but if you see water leaking from the bottom of the tank, then it’s time to replace the water heater immediately as the tank is damaged and is not repairable.

How to Prevent Hot Water Leaks

It goes without saying that the way to prevent hot water heater leaking problems is to do the general maintenance expected for your water heating system.

Treat it right, and it will treat you right for at least the length of it’s warranty — and in many cases much longer.

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Here are some basic, but very effective ways to prolong the life of your water heater:

  • Reduce water pressure to an ideal range of 50-60psi
  • Set temperature to 120F, so tank isn’t running hot too much of the time (Don’t go lower than 120, as bacteria can grow inside tank at lower temps)
  • Test TP Valve once a year. Sometimes sediment can make it hard to open/close. Go up and down a few times to loosen.  Ensure there is a clear, non-threaded (end), unrestricted discharge pipe hanging down with an easy flow area. You don’t want this blocked off.
  • Get to know your water heater: Understand how old it is and any repair history. You can read the labels to find the date if the installer didn’t write it on the outside of the tank. Some labels will show a date in their model number such as: 2347897312Nov to signify the manufacture date of November of 2012
  • Flush for 5 mins ever few months to get out accumulated minerals. Drain completely once a year to remove as much sediment as possible.
  • Use water heater strap kits in earthquake country, so if there’s even a minor earthquake, nothing gets dislodged or cracked.
  • Use a water leak alarm like the one shown on the right. It will obviously detect a water heater leaking from top down as water flows and pools on the floor.
  • Have a qualified plumber (some localities will require plumbers to be licensed) replace your anode rod once every two to five years. The key is to start doing this within the first couple years of life.



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