Troubleshooting Your Tankless Water Heater: What You Should Know Before Calling Your Plumber

There are a number of minor issues that may impact your tankless water heater. Even if you have your tankless water heater installed by a professional, you may find some issues crop up that you weren't expecting. Here's what you should know before you call a plumber.

"Cold-water sandwiches" are normal in some conditions.

A "cold-water sandwich" is a phenomenon that occurs when you've run hot water, and the pipes in the house are full of hot water. Once you stop using the hot water, the tankless water heater goes into cool-down mode. 

But let's say that in the next few minutes, someone decides to take a shower. With hot water still in the pipes, there will be a flow of relatively comfortable water initially, followed by cold water. Then the hot water heater will kick in and deliver hot water again. This can be irritating, but it's not an error with the water heater. Talk to your professional installer about ways you can eliminate this issue if it comes up often in your household.

Water filters need to be cleaned out regularly.

The water filter is just inside the door of your water heater. You can check your manual for the exact location. In most models, the filter simply screws off, so it's easy to clean out

  1. Close the valves by turning each handle parallel to the pipe.
  2. Open the relief valve to remove any excess pressure.
  3. Unscrew the water filter and check for any debris.
  4. Rinse and use a toothbrush or other small brush to remove any debris that doesn't come right out.
  5. Reassemble and turn the valves back on.

A venting problem is shutting down your water heater.

Most tankless water heaters will flash an error code when not working to indicate the cause of the problem. Code 10 may—in some cases—indicate problems with a vent being covered. Here are some reasons:

  • Vent pipe improperly installed.
  • Pipe blocked by snow or something that blew against it in a storm.
  • Pipe blocked by a living creature—birds nest, wasp nest, etc.
  • Pipe covered by a bag, for example, when the exterior of the house is painted and vents are masked off.

If the vent is open and clear, it's possible that your error code is related to the gas combustion or pressure, which may require a professional fix.

Talk to a local plumber, such as Valley Plumbing Company, if you have a different error code or your tankless water heater is not functioning correctly. In many cases, a homeowner isn't able to do repairs on these heaters, so make sure an experienced professional handles any issues.