No Hot Water Comes Out of Faucets. It is Only Cold and the Electric Hot Water Heater is Working.

Answered by LCD: If no hot water at any faucet in the house, and hot water pipe coming out top of heater and the overtemp/overpressure valve coming out the top of the tank at the side are too hot to comfortably hold onto indefinitely (at least when hot water is running), then the heater is evidently working. If just nice and quite warm but not hot, which means the outgoing water at the faucet (when on full hot position) would be warm, not cold, it could be one of the heating elements or the thermostatic control on one of them has failed, which can produce warm but not hot water in some models - in other models one failed element greatly reduces the recovery rate but does not affect the outgoing initial temperature from on at-temperature heater.

Assuming no one has shut down the temperature adjustment on the heater or partly shut down a valve, and that you have cold water coming out fine on cold faucet setting, and that the outgoing pipe from the heater stays warm when water is flowing from a hot faucet, then sounds like a blockage in the heater. Many have plastic filler tubes that sometimes break apart and put floating debris in the tank, which can block the outgoing pipe.

A major buildup of minerals or iron bacteria in the pipes can also reduce the flow to very little, though that would be a gradual decrease, not normally not occur just from one day to the next but can get mostly to near totoally blocked if a chunk breaks free - in that case the outflow when a faucet is on full hot would be quite low, not full flow.

Another cause of very low flow would be a failure in a backflow preventer or expansion tank, blocking the incoming cold water so it cannot get into the tank, meaning little water would come out. In that case, when water is flowing full force from a faucet, instead of the incoming cold water pipe at the heater getting quite cold it would not change and would stay at or around room temp.

A possble cause, assuming pretty much full flow of cold water from the hot faucets, depending on plumbing arrangement, is a one-way valve in a toilet anti-sweat mixing valve stuck open on the hot side, so when hot water is demanded at a faucet it is instead getting cold or mostly cold water backflowing through the mixing valve. If that is the case, when nothing is being run and the toilet has been flulshed recently, one pipe into the mixing valve will be cold, one warm or hot (at least when toilet has been flushed recently) and the output one to the toilets warm during/after a flush if operating correctly. But if when "hot water" is running at a faucet, you instead feel both inlet pipes being equally cold, then the cold water is backflowing through the hot line to a connection to the faucets. This can happen when the backflow valve in the mixing valve sticks open AND there are takeoffs from the hot water pipe feeding the mixing valve, located between the water heater and the mixing valve (which looks like this usually) -

https://www.amazon.com/Industries-109-503RP-Anti-Sweat-Toilet-Valve/dp/B...

Another possible fix if "hot" flow is low (though does not guarantee it will not happen again) is shutting off the cold water inlet valve to the heater, opening a hot faucet preferably above the heater level, then draining some water (a few gallons) into a bucket or with a hose from the drain valve at the bottom of the heater (remembering this is probably 120-140 degree water) - this can sometimes free up any blockage in the outlet piping. Then shut off the drain and open the fill valve - heater should refill and purge some air through the open facuet as it refills. If you do not hear water coming into the tank (and incoming cold water pipe will get colder) or have water coming of the hot faucet then a flow blockage is occurring somewhere. Course, if the existing "hot" flow equals the cold then this is not a blockage issue.

If the above does not help track it down, then you need a Plumber.

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