7 Reasons for Slow Hot Water Recovery - Troubleshooting Water Heaters

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One of the common complaints homeowners in North America have is the slow hot water recovery or reduced hot water supply. With the slow recovery, even simple tasks like dishwashing and taking a shower requires you to wait much longer for hot water to heat up.

And that is not good, because you have a busy lifestyle and impatient teenagers waiting.

If your water heater doesn’t perform as it should, and to avoid wasting energy and water or dealing with bacteria development, water heater troubleshooting is required.

Sometimes fixing a water heater is easy, especially for DIY-ers with the right skills and tools.

But what if the problem is too complex to fix, or you just don’t have time to deal with it and need hot water fast?

For most, calling a professional to repair a water heater is the only option. Or the best option.

Here we’ll talk about 7 typical reasons that can lead to slow hot water recovery and how to improve it.

  1. Insufficient air/flue blockage
  2. Low gas pressure
  3. Orifice too small
  4. Thermostat set too low
  5. Heater too small
  6. Wrong piping connection
  7. Sediment buildup

Insufficient air/flue blockage

Provide proper ventilation to a water heater. 

An adequate supply of fresh combustion air is mandatory for proper and safe gas combustion. In contrast, the insufficient air supply can impact performance, expose home residents to contamination and carbon monoxide poisoning, which is hazardous.

The recommendation is to provide sufficient openings where the location and sizes are suggested by the manufacturer and often found in the water heater’s manual.

According to the manufacturers, the minimum volume of indoor air requires 50 cubic feet per 1000 BTU/HR. Ventilation air can be supplied directly from the outdoor atmosphere or connected room.

Lack of combustion air means low-quality flame, less power to heat water, reduced performance and efficiency.

Check the flue way, flue baffle, and burner for potential blockages.

A water heater must exhaust the products of gas combustion to the outdoors using approved venting and without any obstructions. 

The venting system must be installed according to local or state codes. Only proper installation can provide safe and efficient operation. 

A correctly installed venting system is free of cracks or breakages, sagging, misalignments, or diameter changes.

The symptoms of insufficient air delivery are yellow glowing burner flame and sooting of the gas combustion chamber, burners, and flue tubes.

Contact a qualified person to install a vent system professionally and avoid poor performance and health concerns.

Low gas pressure

Check with your gas utility company to see if there is a gas delivery problem and get an update on the current gas pressure. Once notified about the problem, the gas company will fix the problem if it is on their side.

You can also check if there is a gas leak in your home, using a leak detector, or applying a mixture of soap and water on gas connections. If it bubbles, the leak is there.

Remember, for any gas issues, the recommendation is to call a gas technician.

The low gas pressure leads to improper air-gas fuel mixture and poor combustion, causing lower water heater efficiency and prolonged water heating.

Orifice too small

Check the manufacturer’s manual or the rating plate to see the correct orifice type and size. 

If the orifice on your water heater is clogged up or too small, clean it or replace it with the correct one.

Since natural gas and LP work under different pressures and if you are converting from one gas type to another, the burner orifices, due to size difference, would need to be replaced as well.

This problem happens if a water heater was previously modified or converted from one fuel type to another.

Thermostat set too low

If your water heater thermostat is set too low, it will lead to uncomfortable showers, insufficient hot water delivery, low recovery, and bacterial growth.

To increase the temperature on your thermostat, turn the temperature knob to higher settings to get the temperature as recommended by the manufacturer, and which is between 120 and 125 F. Do not increase it too high as it leads to scalding temperatures and potential injuries.

Some water heaters, such as the electric type, require you to remove an access panel and adjust the temperature with the flat screwdriver or pressing the buttons on the control panel. 

Gas models have a dial on the gas valve assembly, so users can turn it clockwise or counterclockwise to change the temperature.

Tip: If you have a tank-type water heater, don’t expect to see the change right away. It might take hours before seeing the difference. But, if the temperature doesn’t increase after some time, you might have to replace a thermostat.

The water heater is too small

If you installed a water heater when there were only two of you in the household, and since then your family increased, or you have guests, or your habits changed, you would have a situation where a water heater cannot handle increased demand. It is too small now.

Or, you might have a situation where your gas water heater doesn’t have enough BTUs to heat water fast enough.

The solution for these problems is to install a larger unit and get sufficient power or recovery rate.

When sizing a water heater, use the following data, which shows the relation between the number of people and capacity in gallons, or how much hot water one household needs:

1-2 people – 30-40 gallons

2-3 people – 40-50 gallons

3-4 people – 50-60 gallons

>5 people - 60-80 gallons (or more)

You can also buy a tankless water heater with a high GPM rate and enjoy your showers with on demand and endless hot water supply.

Piping connection and dip tube

During installation, make sure that the cold water supply pipe is connected to the cold water inlet (blue ring), and the hot water pipe is linked to the hot water outlet (red ring).

Plumbing crossover is another issue that occurs with the faulty single-handle faucets, mixing and checking valves, and it allows hot water to cross over to the cold side and vice versa, reducing the temperature.

Confirm that a dip tube, which extends from the cold water inlet, is not broken. Dip tubes are designed to bring cold water to the bottom of the tank. If it is broken and cold water exits nearby the top of the heater, it will mix with heated water and reduce its temperature to lukewarm.

Sediment buildup

If you have a gas water heater installed and there is a hard water problem in your area, your water heater might be exposed to sediment buildup. Dissolved minerals in water and higher water temperature can cause increased accumulation on the tank’s bottom. Over time, the sediment layer grows to the point where it can greatly reduce the heat transfer between the burner flame and water. Or between heating elements and surrounding water (electric type).

Because of that, it takes longer to heat the water, or a water heater cannot produce hot water as quickly as it used to.

It is almost impossible to avoid sedimentation in areas with hard water, but you can prevent it.

One way to prevent sediment buildup is to flush a water heater or use a water softener regularly.

Note: There are two recovery rates to keep in mind: manufacturer-rated recovery and actual. The manufacturer-rated recovery rate is found on the EnergyGuide label or in specs for that model. It will give you an idea of how much hot water a water heater can generate in one hour after being completely drained. The actual recovery rate is what you are actually getting while using a water heater.

How to improve hot water recovery rate

If you have a growing family, your water heater should be big enough to meet the hot water demand. If not, there are several ways to improve the hot water delivery rate.

One of the solutions is to install a point-of-use water heater (POU) with a capacity of a few gallons. Hot water is always ready for you to use, and it is ideal for small tasks when waiting for the large heater.

You can also install a recirculation pump and have water delivered in no time.

Another solution is to buy a tankless water heater with or without a recirculation system and enjoy on-demand and endless hot water delivery.

If you want to avoid adding a new appliance, you can try flushing your water heater to remove sediments blocking or preventing proper heat transfer. For those who live in colder areas, make sure to insulate a tank and all exposed pipes.

Did you know?

  • Did you know that you can buy a smaller water heater with a high recovery rate?
  • It takes longer for larger water tanks to recover.
  • A gas water heater can heat water up to two times faster than electric models.
  • Water heaters with the higher first-hour rating – FHR, can recover in less time.
  • The temperature of incoming cold water has a significant impact on how fast water can reheat. If the temperature rise (the difference between the set temperature and incoming water temperature) is higher, the longer the recovery time.

The article covered some of the common reasons and solutions for slow hot water recovery, but there are others as well.

Keep in mind that the life expectancy of a water heater is between 10 and 15 years, and over that time, many problems can occur, including low performance, decreasing efficiency, and malfunctioning components.

Whatever steps you take in solving a problem with the slow hot water recovery, always consult a licensed plumber to assist with repair or installation.

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