Tankless Water Heater Maintenance Everything You Need to Know

Also known as instantaneous or demand-type water heaters, tankless water heaters are more energy efficient as they provide hot water as and when it is needed. According to the US Department of Energy, a home that uses an average of 41 gallons of hot water on a daily basis, a tankless water heater could save 24% to 34% of energy compared to the conventional water heater. However much a tankless water heater is beneficial to your family’s hot water needs, you better not overlook the need for its regular maintenance.

Just as with any other mechanical equipment, maintaining your tankless water heater ensures its lifespan’s longevity and operational efficiency. Manufacturers recommend that this type of water heater be maintained at least once every year. You may need to adjust this to twice or thrice per year if…

  1. Your unit is set to quite a high temperature – this is because most chemicals dissolve at a higher rate when heat is applied. Therefore, the higher your unit’s temperature, the faster the scaling will take place.
  2. You live in an area with extremely hard water – the mineral content in water differs from place to place. If you live in an area where the water has a higher mineral content, the rate of scaling will be much higher.

To have a better understanding of how to maintain your tankless water heater,  let’s first understand how it works.

How a tankless water heater works

As opposed to the conventional water heater where the water is heated and stored in a tank, a tankless water heater works as and when a hot water faucet or appliance is turned on. Cold water gets drawn into the unit through a supply pipe and is heated by the heat exchanger. The heat exchanger transfers heat from the gas-powered burner or electric coils to the water. The exchanger is activated as soon as the cold water starts flowing into the unit.

These type of heaters normally deliver 2 – 5 gallons per minute, with the gas-powered models delivering higher flow rates than their electrical model counterparts. Once the faucet or appliances is shut off, cold water stops flowing into the unit and the heater is turned off.

Tankless water heaters are classified into two: whole-house and point-of-use heaters. As the name suggests, whole-house heaters are large and more expensive as they are designed to supply hot water to multiple outlets. As the tankless water heater delivers the hot water on demand, a whole-house heater never runs out of hot water unless the flow surpasses the system’s ability to heat it. For instance, a tankless water heater will conveniently serve two people taking a hot shower simultaneously. However, they might be in for a relatively cold shower should someone else start the washing machine.

On the other hand, a point-of-use heater is designed for one or two outlets such as your kitchen sink. They are compact and can be fitted under a closet or cabinet. They are advantageous as their installation near the outlet reduces the lag time. This is the amount of time taken by the hot water to get to the outlet.

Tankless water heater systems are estimated to last as long as 20 years. This is a worthwhile investment particularly if you own the home or you are intending to stay in your current residence for quite long. Nevertheless, without proper maintenance, your unit will not last that long.

Tankless water heater maintenance

While this type of water heater is mostly marketed as low-maintenance, this could not be further from the truth. The primary maintenance practices you have to observe are descaling and flushing.

Descaling a tankless water heater

Over time, mineral deposits accumulate on the inside of the unit’s heating chamber. This makes the unit inefficient and if left unattended, could inhibit flow. This buildup causes your unit to overheat which can further damage it. For this process, you will need a descaling kit such as J.C. Whitlam FLOW-KIT Flow-Aide Descaler Kit. The kit has a 350 GPH pump, a 3.5-gallon bucket, 2 rubber hoses, and 1 quart of flow-aide (FLOW32) which is the descaler.

How to go about the descaling process

  • Make a solution by dissolving the Flow-Aide in water as per manufacturer’s instructions and set aside.
  • Turn off the power to your unit as well as its valves to ascertain that water does not spill out of the heater.
  • Turn the hot and cold valves off to prevent the flow of water through the system during the process.
  • Remove the hose threads from the cold and hot water ports and attach the two hoses in the kit.
  • Dip the pump into the already made solution and attach the cold water hose to the pump while the other hose’s end should be in the bucket, thus creating a loop.
  • Take the pump’s cord and plug it into a socket and turn it on to commence with the descaling process.
  • Leave the pump running for 45 minutes to an hour, during which time you might notice some foam forming on the bucket or the solution appearing cloudy. This is as a result of the Flow-aide reacting with the scale within your system.
  • Turn the outlet and inlet valves off and disconnect the hoses. Turn on the cold water valve and let the solution within the system run off for around 5 minutes. Remember to place a bucket beneath its outlet if your heater is indoors.
  • Clean the screen on your heater’s underside using the solution and screw it back on.
  • Turn on the hot water valve as well as the power and test your unit’s efficiency.
  • Dispose of the used Flow-Aide solution in accordance with the local laws.

Flushing a tankless water heater

Flushing your system works in the same way as descaling, but in this case, you use of vinegar. Put at least 3 gallons of water in a bucket and immerse the pump. Follow the procedure as outlined above. As the procedure makes use cheap items, you can perform it as much as three times a year. Should you want to avoid having to flush your unit all too often, you could install a water softener.

When do I know it’s time to descale or flush my tankless water heater?

Just like any other device in the household, your tankless water heater could fail from time to time. Some of the common signs you should look out for include:-

Varying water temperatures

Does the temperature of the hot water fluctuate from being hot to being cold, and hot again in the span of a single wash or shower? Your unit could be having an electrical fault especially if you are the only person within the household using hot water. Loose electrical connections are the primary source of this issue. If all the visible tankless heater elements are tightly secured, you might need to call in a professional to diagnose what the problem is.

Another, if your system is producing warm rather than hot water, this could be as a result of too much pressure. If the flow rate of the incoming cold water is too high, the heat exchanger becomes overwhelmed and is unable to effectively heat the water.

The unit is shutting itself off

If you have an older unit, the problem could be a minimum flow rate that is too high. The minimum flow rate refers to the capacity of water that needs to flow through the unit every minute to produce hot water. In this case, the unit of measure is gallons, therefore, it is measured in gallons per minute (gpm). Older units have a minimum flow rate ranging from ¾ to ½ gpm while newer unit run with as little as ¼ gpm.

If the output of hot water is below your unit’s minimum flow rate, the unit could be shutting itself off for safety reasons. This is because the insufficient water running through the system could cause overheating. If the problem persists, you could as a professional if you can upgrade your unit.

Tankless heating units must also be vented to avoid automatic shut-downs. The units have very hot exhaust which, when restricted could result in shutdowns. Check that the venting tubes are not too lengthy or convoluted.

Strange noises within the unit

A tankless water heater is intended to function as quietly as possible. In the event of creaking, rumbling or popping noises, your unit is up for maintenance. This is mostly as a result of mineral buildup which results in your unit using more energy to heat up the water. It also reduces the water volume your unit is supposed to hold.

Should the noise persist even after you flush you it, it could signify a serious problem. Your unit could be on the verge of a leak or crack. In that case, you may need to replace the unit as soon as possible.

Strange color or taste in the hot water

Does the hot water look cloudy or rusty? Do you notice a metallic taste or scent in the water? These are signs of a failing unit. Cloudy hot water implies that the mineral deposits are traveling out of your unit and flowing out of your types. In this case, flush or descale your unit as soon as possible.  Rusty water means that your unit could be rusting on the inside. This is a potentially serious problem that should be dealt with immediately.

A leaking valve

Do you notice signs of wetness around your unit? This is a sign that your unit is leaking. Inspect the valves and tank to diagnose where the leak is originating from. If the leak is from the tank, it implies that its lining has been corroded. Plan on replacing the unit. If it is from a valve, you will only need to replace it and not the entire unit. Shutting off the water supply to your unit will be a temporary solution.

Carrying out preventive maintenance ensures that your unit remains reliable and consistent by taking care of minor problems that could have developed to major repairs. Should you be unsure on what you should do, involve a professional.

The more regular the repairs become, the more expensive they are. Should you notice the time between repairs is becoming shorter and shorter, it might be time to get a new unit. This is especially the case if the current unit has outlived its lifespan.

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