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Is there anything more annoying than hot water drying up on you in the middle of a shower? Actually, there is – having to finish your shower with cold water because the hot water may take up to 2 hours to resume flow depending on your water heater’s specifications.

You see, as much as a hot water heater seemingly works magic to keep hot water running in your shower, faucet, dishwasher, and washer, it takes time for the water to heat. Often, if the water heater is functioning optimally and the volume being outputted is sufficient for the house’s demand, you may never experience any hot water outage.

However, if the heater has some issues or the hot water demand is more than the heater can heat in the given time period, then it is inevitable that your hot water taps will run dry.

If that happens, what should you do, and how long should you expect to wait before hot water flow back to your taps again? If there are no underlying issues, there is nothing you need to do. Hot water should start to flow into the house once the heater has recovered.

There really is no definite timeline for how long the heater will take to heat the water. It can range between 30 minutes and two hours or even more depending on whether there are more complex reasons that led to the shortage in the first place.

Below, we will discuss tentative timelines and factors that influence how long a water heater takes to heat the water. We also discuss why the water heater may take longer than expected to recover and what to do if that happens.

Factors Determining How Long a Water Heater Takes to Heat Water

Many factors determine how long your water heater takes to heat water, as discussed below:

Type of Water Heater

The average gas heater takes about 30-40 minutes to heat water in the storage tank. Electric heaters take, on average, double the time a gas heater takes to heat the same amount of water. This is because gas burners produce more energy, and consequently, the water reaches higher temperatures faster.

On the other hand, electrical coils used to heat water in the electric water heaters take longer to get hot and produce less energy. As such, you can expect it to take one to one and half hours to recover.

Solar heaters leverage electric water heaters, so it will take them a similar amount of time to the electric water heaters to have heated water. Tankless water heaters are uniquely designed to heat water on demand; therefore, you do not expect to have a sudden water outage.

Capacity of the Heater

The higher the water heater’s capacity, the longer it takes to heat water. For instance, it will take longer to heat 50 gallons of water than it would 20 gallons. Keep in mind that although smaller heaters will heat faster, the water is likely to run out again if the demand is still high.

First Hour Rating (FRH)

The FRH indicates how many gallons of water a heater can heat up within the first hour of being put on. A higher rating is an indicator that the water heater will take a shorter time and vice versa.

Draw Efficiency

A water heater’s draw efficiency refers to how much hot water goes out as cold water comes in.  Both electric and gas heaters have a 70% draw efficiency per tank size. For instance, if a water heater has a 50-gallon capacity, it has a draw efficiency of 35 gallons.

Inlet Water Temperature

The temperature of the water coming into the heater’s tank can significantly affect recovery time. If the water temperatures are extremely low, it will take more energy and time to heat the water in comparison to if the water is at room temperature. Extremely cold water is common during winter or if you live near the northern hemisphere.

Once the water is heated, two other factors may affect how long it takes to get to your appliances or fixtures. These are the distance between the heater and the appliance and the diameter of the pipe.

The longer the distance between the water heater and the appliance, the longer it will take to get to your appliance. The case of a pipe’s diameter is two-fold. The wider it is, the more water it will ferry to the appliance, therefore a faster delivery. However, it requires more water to have been heated up to a significant temperature for enough pressure to build up so that it flows.

Similarly, if your tank is located in a garage or attic with a cold temperature, this can create a similar “work harder” effect on your unit. If your tank has a low insulation R value under 24, consider using a water heater blanket to help retain heat.

Why Is the Water Heater Taking Longer Than Usual to Recover?

Even after allowing enough time for the water heater to recover, you may notice that it is taking too long. If this happens, there may be other underlying issues that vary depending on the type of heater and, therefore, different resolution steps.

Causes of Slow Recovery Time in Gas Water Heaters

Slow recovery time in gas water heaters is mainly due to no gas supply to the water heater. This can be as a result of the gas supply being interrupted or turned off.

To troubleshoot, put the gas knob to pilot and remove the cover to the heater’s side panel. Check whether there is a flame. If not, the pilot light has gone off. To resolve, turn off the regulator for 5 minutes, then switch the regulator to pilot.

Hold down the self-ignite feature for a minute and switch the regulator on. If the heater uses a glow plug or spark ignitor, direct it to the pilot burner on the gas supply tube. The pilot light should ignite.

Otherwise, the gas inlet valve may be closed, interrupting the flow. If that is the case, turn the handle parallel to the gas line and attempt to put on the pilot light. Still, if it does not light, the thermocouple could be defective, in which case you need to get in touch with the utility company. Meanwhile, check for gas leaks.

Causes of Slow Recovery Time In Electric Water Heaters

Slow recovery time in electric water heaters may be as a result of:

Tripped Breaker

Check whether any of the water heater switches are off or a circuit breaker that is not in line with others. If you find one that has tripped, put it on. If it trips again, there is an underlying issue, and you should contact a qualified electrician.

Note that electric water heaters require their own power source as they demand a lot of power. Therefore, if you do not have a dedicated power source, it could also cause tripping.

High Temperature Cut Off

The high temperature cut off switch goes off if the heater exceeds a set temperature. You can reset it from the heater’s panel, and the heater should resume heating immediately. If the heater does not resume heating, the chances are that the switch is defective and needs to be replaced by an electric water heater expert.

Water Inside the Panel

The panel should always be dry in case water enters the compartment. It can cause some of the water heater’s wiring to short circuit. Inspect for water spillage in the panel with caution to prevent the risk of electrocution. If there is evidence of leakage, it is time to replace the heater as the leakage is likely to worsen.

Faulty Heating Element

An electric water heater works so that the heating element gets hot and transfers the heat to the water in the storage tank. If they are faulty, the water remains cold, in which case you should contact a professional plumber to replace the heating elements. The average electric water heater lasts 10-15 years, but fixing individual parts can help prolong its overall life.

Why Does My Hot Water Supply Keep Cutting Off Recurrently?

Recurrent incidences of hot water outage or slow water heater recovery may result from mineral build up in the storage tank. This covers the heating elements inhibiting heating. Excessive build-up can be minimized using water softeners if the inlet water is hard, installing and regularly replacing anode rods, and regularly flushing the heater tank.

It could also be a sign that the water heater tank has done its time and needs replacing. Common signs of a worn-out water heater include higher than usual energy bills, hot water running out fast, evidence of leakage on the water tank, and rust and corrosion. Finally, your hot water needs may be more than the heater’s capacity, which overworks it.

In conclusion, if your hot water tap suddenly runs dry while showering, finish up with the cold shower as the water heater will take some time to recover. An electric heater takes longer than a gas heater to recover.

If the heater takes too long to start heating again or does not heat at all, you can troubleshoot for causes such as lack of gas supply, thermostatic tripping, or water alarm tripping, among others.

However, it is best to contact a professional to troubleshoot and resolve the issue. If your heater’s warranty is almost up, then you need to start thinking about replacing the heater.