Tankless Water Heater Maintenance

Here’s everything you need to know about tankless water heater maintenance.

Does your home use a tankless water heater? Have you recently switched from a traditional tank to tankless? Even with a tankless heater, regular maintenance is required for it to run properly.

Knowing how to maintain your boiler will help you understand how it works. Sometimes, issues can then be resolved without the need to call a professional.

Hourly rates for professionals aren’t cheap. So, even if you still need to call a professional, identifying a problem first means they will be able to go right to it.

We’ll go over some of the most common problems that can be prevented or identified early by regular maintenance. Yes! You can save a little money by not calling a professional every time.

Importance of Regular Maintenance

As with any other appliance in your home, you can run into issues with your tankless water heater. They may be easier to maintain than traditional tanks, but that doesn’t mean you can ignore them after installation.

Performing regular maintenance checks will identify problems or stop them from escalating.

Preventative maintenance will mainly consist of cleaning the different parts of your tankless water heater. It also includes checking fittings and descaling and flushing it out annually.

Descaling and Flushing the System

Over time, water heaters can get scaling and other issues from hard water. Luckily, descaling and flushing your water heater unit are simple as long as you have the right tools. Here’s how you can do it.

  1. Make sure you have a sump pump, a five-gallon bucket, and a standard hose set.
  2. Check that your tankless water heater has a flush kit installed. If no flush kit is installed, you’ll need to contact a plumber to install one. A flush kit is essential if you want to perform proper maintenance.
  3. Turn off both the gas and water supply. The electricity should stay on.
  4. Drain both the hot and cold water supply. You’ll likely have more cold water than hot water draining.
  5. Take out the prefilter and check if it’s clean. If it’s clogged, clean it before flushing.
  6. Pour three gallons of distilled white vinegar into your five-gallon bucket.
  7. Put your sump pump at the bottom of your bucket with the vinegar.
  8. Connect the other end of the hose to the cold side and run the other hose through the hot side and back into the tank.
  9. Plug the tank in and let it run for one hour.
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Other Common Tankless Water Heater Problems

1. No Hot Water

Not having hot water at all is perhaps the most common issue you’ll face with your water heater. If there’s a fault, it is usually one of three things:

  • Lack of power.
  • Faulty thermostat.
  • Faulty upper electric heating element.

If this is happening to you, make sure to check the power and water supply. Resetting tripped breakers or replacing broken fuses will resolve issues with electrical power. After this, check the thermostat.

Take Note

If you have a gas tankless and think your gas supply is faulty, call a professional immediately.

If your thermostat is receiving power, but still isn’t working, you may need to replace the thermostat and the heating element.

Other common causes of no hot water could be frozen pipes, a partially opened tap, or closed shut-off valves.

2. Water Isn’t Hot Enough

This is another common issue that may arise. If your water is too cold, it could be due to a few reasons. Your thermostat or heating element could be faulty as stated above. It could also be due to too small a unit or crossed hot and cold connections.

Warm or cold water could mean your unit’s flow rate can’t keep up with demand. A simple test is to try running one appliance to see if the water temperature is okay. Turn on a second, then a third until the temperature starts to decrease.

Has the hot water demand in your household changed? This could mean your peak demand is higher than your unit can deliver. You’ll need to look into getting an additional unit or replacing your current one with a bigger size.

To check for a crossover, turn off your water supply, then turn on your hot water faucet. If there isn’t water flow, you don’t need to worry. However, if you still have water flow there is an issue. Follow these steps to check for a crossover.

  1. Shut off cold water entering your unit: no water will flow into your faucet after this.
  2. Open all the hot water valves in your home: leave them open for 10 minutes. There shouldn’t be any water coming through these.
  3. If water is present, a crossover is your issue.
  4. Locate your bad faucet cartridge: turn off all faucets. One at a time, turn on and put your ear up to all single handle faucets to locate the source.

3. Too High Temperature

If your water is too hot, lower the temperature on your water heater thermostat. If this doesn’t work, check your water temperature sensor as it might be broken or improperly positioned. You can try repositioning it so it’s firm against the pipe, or replace it if it’s broken.

4. Unit Is Noisy

If your water heater is noisy, check the fan. There may be debris stuck in there, so cleaning it out should help. Depending on the pitch of the noise, it may be another issue.

Low-Pitch Hum

A low-pitch hum usually means the water inside is boiling. This is caused by sediment build-up in your system. You can fix this issue by flushing the system out.

High-Pitch Whining

If the noise is more high-pitched, it could be due to scaling inside your system from a build-up over time. To take care of this, flush the water heater and then clean the elements.

For more heat-transfer efficiency, it’s worth installing low-watt density heating elements with a larger surface area.

5. Water Leaks

Leaking is another issue you need to be aware of. If you see a leak in your system, it could potentially be a major problem. A few different things can cause leaks.

  • Faulty temperature & pressure relief valve: Flush the system and if the leak persists, it will need replacing.
  • Too much pressure: Lower the thermostat setting and check for loose pipe connections. Tighten any loose connections you find.
  • Leaks from the plumbing: This may just mean you need to tighten the pipes or use plumbers tape to hold them together.
  • Loose heating element bolts: Tighten any loose bolts and if the leak persists, replace the gasket.

Take Care of Your Tank!

Perhaps the most daunting thing about being a homeowner is having to maintain your household appliances. You become responsible for taking care of things when issues arise, and that can be stressful. That’s why regular maintenance is so important.

By performing regular maintenance checks on your tankless water heater, you can prevent major issues from arising. As long as you remember to descale and flush the system at least every 12 months, you’ll take care of most potential problems.

Do you perform regular maintenance on your tankless water heater? Are you going to do so now that you’ve read this article? Let’s hear it in the comments.

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About the Author

Peter Gray

Peter has been a homeowner for 35+ years and has always done his own repair and improvement tasks. As a retired plumber, Peter now spends his time teaching others how they can fix leaks, replace faucets, and make home improvements on a budget.