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Electric Tankless Water Heater: DIY DeScaling 2020

In CategoryTim Whitcombe
ByGardenAdvice Tim Whitcombe

A tankless electric water heater does not require a tank to store hot water. It’s also called an instant water heater. These heaters heat up the water “on demand”. This means the water’s temperature rises only when a hot water tap opens anywhere in the house. The system ignites and the flame heats the passageways of running water. Providing instant hot water. For installation and a basic comparison between a tankless and tanked water heater refer to the youtube link.

WaterFiltersAdvisor published a post about tankless water heater maintenance. Though these systems normally last very long, to keep it running smoothly it is always a good option to know a few simple tricks. This will not only increase the life expectancy of the product upto 25-30 years but also sustains its quality so you can use it with its full capacity.

Some common issues that can occur over time are:

  • Mineral Build-Up
  • Air Supply or Exhaust Blockage
  • Ignition Failure
  • Flame Failure

Mineral Build-Up: 

In the areas where hard water consistency is higher, minerals like calcium and magnesium start depositing on the inner walls or in water pipes inside the heater. This can cause blockage of water. Bits and pieces of these minerals can travel through the pipes along with the hot water and cause problems in the showers or kitchen faucets.

Another way to cope with this situation is a method called Water Heater Flush. This process is suggested be done once a year to maintain the functionality of the heater. 

FYI, the positioning of heater valves may differ depending on the brand you are using. However, the mechanism is the same for tankless water heaters and the same process is applicable.

Things you need:

  1. Undiluted White Vinegar (3-4 Gallons)
  2. Submersible Pump 
  3. Standard Sized Bucket (for flushed water discharge)
  4. Hose Kit (Use the attached link to purchase the water hos or choose the one that is suitable for your tankless heater)
  5. Plyer (to help unthreading the valves caps or the filter chamber)

Instead of the items listed above, you can also purchase EZ Flush Kit to carry on with the DIY process. This kit comprises of: 

  • 350 Gallons Per Hour Pump
  • 1 quart of Eccotemp Descaling Solution (substitute to white vinegar). 
  • 2×5-foot Rubber Hoses (one is to connect to the pump and the other one  pours the cleansing solution back to the bucket for circulation).

How to Descale The Heater Tank:

Step 1:Cut off the electric supply to the heater and unplug the switch for safety.

Step 2: Close the hot and cold water valves. The valves need to be perpendicular to the pipes. That’s when the valve is closed. These valves let the cold water (blue valve) enter the heating tank and the hot water (red water) is then released and distributed to the house outlet.

Step 3: Open the flush kit’s valves to drain the water from inside the heater tank.

If the flush kit is not installed under the heater, call the plumber to have these installed as descaling is not possible without these.

Step 4: Check the prefilter for any kind of debris. If the filter needs cleaning refer to a 3 minutes Youtube video. If you find no debris in the filter, plug the filter back to its place.

Step 5: Fill the bucket with the white vinegar. The acidity can be almost 5%. (In case you are using the chemical solution for the cleaning process instead of vinegar, the following step is a must. Make sure to flush the solution out of the tank thoroughly otherwise it will get mixed in the water distributed inside the house. The video demonstrates this process efficiently).

Step 6: Place the circulation pump in the bucket. Try to place a block inside the bucket so that only the base of the pump submerged in the vinegar.

Step 7: Connect the hose of the pump to the cold side of the flush valve first so the vinegar passes through the filter first cleaning it thoroughly. Connect the hose kit to the hot water valve and drop the loose end back into the bucket. Make sure the hose heads are threaded securely to the valve to avoid leakage. (This circling process will loosen the deposits from the inside and the circulation pressure is going to push the waste material out).

Step 8: Turn the pump on and let the vinegar circulate the system for almost an hour to an hour and a half.

Step 9: After approximately an hour, turn the pump off. Change the hose to the alternative valves i.e. pump hose attached to the hot water valve and hose kit attached to the cold side valve. Leave the pump running for another hour. (The circulation of solution instead of vinegar takes about 30 minutes, which is half the time vinegar takes to clean the tank completely).

Step 10: Once both the valves go through the same process. Remove the kit hose and the pump hose from the hot and cold valves. Close these flush valves with their caps.

Step 11: Now turn the hot and cold water supply valves open and close the flush kits valves.

Step 12: Turn the gas valve on. Plus the switch back to the power and switch it on too.

To watch the complete process refer to the Youtube video


  • This process takes approximately 4 hours. Including the initial preparations and the exchanging of hoses in the midst of the process. 
  • It is a very simple process and one person carries it with ease. Heavy duty tools are not required. 
  • The supply items purchased are usable multiple times. These will help you maintain the heating system you currently have for many years to come. 
  • When it’s time to replace the old system with a new tankless heater, usage of the tools again is possible to keep the heating system running efficiently. 
  • When using the solution instead of vinegar, be extra careful. Wear gloves to protect your skin from any kind of interaction with the chemical. 
  • Use water softener to reduce the depositing of minerals in your heater tank. Refer to the Youtube video for more information regarding water softeners.



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