We have a leaking water heater.

Check if the TP valve is running water, and replace TP valve. Check if there is water leak somewhere
http://waterheatertimer.org/How-to-replace-TP-valve.html
Replace both thermostats and both elements, and then keep temperature turned down.
http://waterheatertimer.org/How-to-replace-thermostat-on-electric-water-heater.html
http://waterheatertimer.org/How-to-replace-water-heater-element.html
Add a comment and describe what you find.

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Why is the home inspector removing cover on a water heater?
He might be going overboard to provide good inspection, but my experience says never mess with something old or it will break next day and you get blamed.
He could have made visual inspection for leaking, and checked if water was hot by opening drain valve and TP valve ... but he might cause a drip doing that.
He shouldn't open any appliance.
Did the inspector cause the problem? Maybe yes, or maybe not.
Maybe he helped solve a bigger problem that was looming but hadn't happened yet, and it forced you to get a new heater which you probably feel more comfortable with.
http://waterheatertimer.org/How-to-maintain-water-heater.html

Call the manufacturer about warranty coverage. manufacturer appears on label on side of tank.
http://waterheatertimer.org/Water-heater-manufacturers.html
Troubleshoot resources:
http://waterheatertimer.org/How-to-troubleshoot-electric-problems-with-water-heater.html

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Question is unclear.
What is a vacuum valve?
You posted under electric water heater.
Water heaters are associated with TP or 'safety overflow' valve, water shut-off valve, tank drain valve, pressure-regulating valve, mixing valve and possibly a few other plumbing valves.
Vacuum valve implies that a compressor is creating pressure on one line while creating vacuum on another line. I don't know of a water heater that uses air compressor.
Open following link to help troubleshoot leaking water heater:
http://waterheatertimer.org/Leaking-water-heater.html

If you mean the drain valve, then buy garden hose cap at home center.
Cap will have rubber washer that seals tank.
If drain valve is plastic, the cap may not thread on without sanding down end of plastic drain valve.
Otherwise replace drain valve, which is simple if drain valve is brass, but can be difficult if drain valve is plastic.
Turn off power to water heater: Electric: turn off circuit breaker. Gas: turn knob to pilot.
Turn off water, open bathtub spigot on Hot side, drain water heater, remove drain valve with wrench.
If plastic drain valve breaks while being removed, then 'gently' break out broken part using hammer and big screwdriver.
Buy new drain valve at box store in water heater department.
Put teflon tape on new drain valve threads.
http://waterheatertimer.org/Water-heater-is-leaking.html
http://waterheatertimer.org/Water-heater-will-not-drain.html
http://waterheatertimer.org/Clean-sediment-out-of-water-heater.html

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For a price, expert works with you while you work on water heater or any do-it-yourself project.
Fixya is always less expensive than a service call.

If I understand correctly you have residential electric water heater, and your shut off valve located above water heater on cold-water line is leaking?

1) Hot water would come out of this valve if it's leaking because water inside tank is hot and under pressure ... also remember, hot water rises so tank is probably heating the water inside the cold line during hours when no hot water is being used.

2) You probably need to replace the valve. But if water is leaking because a pipe is rusted, the valve may be ok, and just the pipe needs to be replaced.
Take a photo of your problem to hardware store or home center.
I used to work in those stores and could help folks get the right parts.

3) Here are some steps for replacing the valve.
Shut off main water source into house. This is usually located underground in same box where meter-reader looks at meter.
Your water heater shut off valve is called a gate valve, and it will be 3/4"
All water heater pipes are 3/4"
You will need two 10-12" pipe wrenches, maybe a new gate valve, maybe a new flex connector, probably short 3/4 pipe pieces, teflon tape for each threaded pipe.
Hardware store or home center can get you the right materials, just take a photo over to hardware store

4) When you get started, turn off water heater circuit breaker for a couple hours so water will cool down. You don't want to get scalded with hot water.
Do NOT drain the tank.
Simply open a bathtub faucet on hot side to release pressure.
When finished, turn on the water, and make sure water is flowing out of tub spout in full stream before turning circuit breaker ON

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Fixya is always less expensive than a service call.

Here are a few tings to look for:
When COLD WATER comes into the heater, it might cause sweating of the Cold water line, if the humidity is high in the house? This is usually in summer time only-- when the humidity inside the house is higher..

Another possible place, is the relief valve:
If you have a check valve or two in the system, that ends up trapping all the COLD water in the tank, as it goes thru its heating cycle, -- the Cold water expands, and has to be relieved-- Thus the relief valve will spit out a puddle of water keeping the pressure at a safe level.
(However-- usually the system has a drop pipe coming out of the relief valve-- so likely you would have said that the puddle was at the bottom of the drop pipe-- and you probably would have suspected it..)

However-- Do these suggestions give you some ideas of where the water puddle is coming from ?
Tell us more-

Mack B

Water heater explosions are extremely rare.
I do water heater research including insurance data on water heaters >>> the insurance industry has no reports that I've ever seen of exploded water heaters.
The water heater manufacturers experimented on prior generations, so now our water heaters are safe.
You can turn the water heater off when it is not being used.
You can also set the temperature to a modest 120 degrees and then the water never gets hot enough to cause any problem with the TP valve (drain pipe) or any problem burning you when you use hot water.
http://waterheatertimer.org/How-to-adjust-water-heater-temperature.html

If you have a gas water heater, the TP valve will start dribbling water if there is ever a overheating event. So you will see it starting to get bad and then you can report the problem to your landlord

If you have a electric water heater, electric water heater has 3 safety features.
1) The circuit breaker
2) An energy cut-off red reset button located behind the top panel.
3) The TP valve

Here's another solution. Put a metal paint can or metal pot under the TP valve pipe where it comes down to the floor. Do not cap off this pipe.

My last solution is one my friend took when draining his water heater in a rented trailer. He drilled a hole in the floor. Your TP valve should exit the trailer. His solution might not be right for you. But take some photos of the problem and keep them in store in case the landlord refuses to refund the deposit.

Rest well. Every trailer, and every home has a water heater. I worked in the trades for 30 years. I never saw or read of one exploded water heater except the mythbusters video on U-tube (which is entertaining and shows how far a water heater has to be pushed before there is a problem).

you can use a residential water heater, just make sure it's the correct amperage/power draw for your circuits.

Rachel,

I don't know if you have resolved your issue by changing the T&P relief valve. However, if you have replaced it and it appears to have resolved the problem ... it will most likely be only a temporary resolve. And what has happened, it that the water that was being relieved via the T&P valve is now unknowingly leaking / being relieved by a toilet or some other means.

The reason of the leak in the first place is that the most likely the water purveyor has recently installed a DCV (dual check valve) at or within the water meter location. Not knowing where you live, but we are in NC and these DVC's are being installed all over the country.

Basically, your home's plumbing system used to be an "open system" and not it is a "closed system". In earlier times, when the water heater cycled it heated the water, which cause the volume to thermally expand ... and the water was pushed backwards through the meter and it did not allow the water pressures to build. However, with the DCV installed ... now when the water heater cycles and expands water, with no place for the excess water volume to migrate, it now causes a hydraulic effect within the closed system ... which causes the water pressure to become elevated, ultiamtely being relieved at the T&P ...

Here are a couple of links from Watts ....that will help.
http://www.watts.com/pro/divisions/watersafety_flowcontrol/learnabout/learnabout_thermexpansion.asp

http://www.watts.com/pro/divisions/watersafety_flowcontrol/support/support_DETsizing.asp


Locally, we have been on the Cross Connection / Dual Check Valve crusade since early in 1991. We concur that the check valves warrant installation. However the Buidling / Plumbing Codes are not up to speed with truly what is going and how much damage to personal property is occurring with failed water lines ... both inside the home and outside.

Best, Gary H.

Hestand Associates / [email protected]