What happens when the water source to a water heater is turned off?
Posted on | May 4, 2010 | 4 Comments
If the main water is shut off, what happens to the water heater? No one will be using the hot water anytime soon.
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4 Responses to “What happens when the water source to a water heater is turned off?”
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May 4th, 2010 @ 6:01 pm
As long as the water heater is full of water, there should be no damage to the heater. If no one is going to be using the water for a while, weeks to months, then I would also turn off the water heater, you will save on the cost of having to heat water that will not be used and in case there is a leak or leaky faucet, then you will not damage the heater by heating an empty heater.
May 4th, 2010 @ 6:28 pm
The Temperature of the water is controlled by a thermostat and would still kick on and off and could steam the water level down and burn your heating element out and you would have to replace the element most times, But it is a good ideal to disconnect the water heater if it is electric and if it is gas to cut off the gas supply, that way your water heater will be OK when ever you come back even if it is a year or so.
May 4th, 2010 @ 6:50 pm
It’ll keep cycling and heating. Tunr off the gas to it as well. Otherwise, the water could evaporate and leave it to burn out the bottom.
May 4th, 2010 @ 7:38 pm
Its a dangerous thing to shut off the water to a water heater and leave it off for prolonged periods of time. .
What can happen is that an “air gap” can occur at the very top of the water in the tank. In that air gap, free hydrogen and oxygen from the warm/hot water will form and any sort of a spark or ignition can cause that mix of air and hydrogen to explode.
Explosions in water tanks from accumulated hydrogen are more common than one thinks. A few years ago here in the midwest, a unused hot water tank accumulated enough free hydrogen to blow up a mobile home and set it afire and kill its occupant. You can view the possibilites of such a hydrogen accumulation on the Net which more fully explains the dangers of that occuring.
Aside from the possible hydrogen problem, the possiblity of the thermostat malfunctioning and the water tank overheating is moreso than a full functioning tank with pressure on it. An overheated water tank will produce large quantities of steam and which at first will blow out of the pressure relief valve causing possible damage to nearby walls.
It is always a good safety rule that when one shuts off the water pressure to shut down the water heater. If it is electric, pull that switch, if its gas set it to pilot.
If you have had your water off for months, purge out the air from the entire system, that will purge any possible hydrogen from the tank and lines itself before you throw any electrical switch or put the gas onto the heater.