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Descaling Procedure for Tankless Water Heaters

Posted: February 25, 2022

Tankless water heaters are an excellent alternative to traditional hot water tanks. The water heats instantly as it passes through the unit, providing an unlimited hot water supply while using far less energy. While tankless heaters require less routine maintenance than a traditional water heater, they still need to be descaled periodically for optimal performance. While it’s possible to complete this job yourself, we suggest hiring a professional to avoid descaling a tankless water heater incorrectly. 

Why do tankless water heaters need to be descaled?

Water contains essential minerals such as calcium and lime. When water runs through any machine or appliance, the calcium and lime collect and erode the metals inside the device over time. This build-up is referred to as “scale.” 

While tankless models gather less scale than traditional water tanks, it does still happen. As scale collects inside,  it makes the tankless water heater slower, affecting its performance and reducing its efficiency. If scaling is ignored for too long, serious problems can occur. Likewise, the tankless water heater comes in direct contact with your home’s drinking water, making maintenance that much more critical.

What happens if you don’t descale tankless water heaters?

Luckily an electric tankless water heater doesn’t pose the risk of exploding due to extensive scale build-up, unlike traditional hot water tanks. Nonetheless, tankless water heater maintenance is an essential aspect of routine home care that shouldn’t be ignored.

Scale build-up stresses the unit’s heating elements and forces the heat exchanger to work harder, using more energy while pumping less water. Even a thin layer of scale can increase energy consumption by thirty percent. If the tankless water heater isn’t descaled, it will cost more money and disrupt a home’s hot water supply.

Descaling procedure

Descaling a tankless water heater is more complicated than descaling a traditional water tank. However, a professional plumber in Sacramento can complete the procedure in a short period. Your plumber will have a descaling kit that includes:

  1.  a five-gallon bucket
  2. three to four gallons of food-grade vinegar solution or descaling solution
  3. two ¾ inch drain hoses
  4. submersible pump

This is the process followed to descale a tankless water heater:

  1. Your plumber will start by turning off the heater, disconnecting the power cord, and gas supply if applicable. Followed by the main isolation valves that allow the cold water to enter and heated water to exit.
  2. Next, they will open the purge valves to relieve any built-up pressure before turning the drain valve lever handles to remove excess water inside the unit.
  3. Your plumber will connect one drain hose to the submersible pump, placing it in the five-gallon bucket underneath the water heater before attaching the other end to the cold water drain valve outlet. They will connect the second hose to the hot water drain valve with the opposite end in the empty bucket. 
  4. Then they will add vinegar or descaling solution until the pump is completely submerged.
  5. The cleaning solution is then circulated through the heater for at least an hour to remove the scale buildup. The solution will pump into the tankless water heater through the cold water valve and circulate back into the bucket through the heated water drain valve.
  6. After the tankless water heater is clean, your plumber will remove the pump and drain hose from the bucket and close the cold water drain valve. They will then empty the bucket before putting the hose connected to the heated water drain valve back in.
  7. Your plumber will then open the cold water main valve and allow fresh cold water to flush the tankless water heater of any residual solution through the hot water drain hose into the bucket for about five minutes, or twenty gallons of water.
  8. Once complete, the red drain valve will be closed before removing the connected hose and opening the main valve to test the unit. The descaling procedure is now complete!

How often does a tankless water heater need to be descaled?

The water hardness in your area plays the biggest role in determining how often you’ll need to descale your tankless water heater. Water hardness is determined by the mineral levels in an area’s water supply. Areas with hard water require more frequent descaling due to higher levels of scale build-up. To be safe, we recommend descaling tankless water heaters annually as per the manufacturer’s suggestion.

We can professionally descale your tankless water heater in Sacramento

Sacramento Plumbing Solutions offers professional tankless water heater descaling throughout the Greater Sacramento area. Maintaining your tankless water heater with regular descaling will reduce energy costs and prevent unnecessary damages. If you’re interested in switching to a tankless water heater, we’ll provide a free consultation before scheduling your tankless water heater installation. Send us an email or give us a call today!

Mike Grijalva

Mike Grijalva

Owner and lead plumber at Sacramento Plumbing Solutions. Mike has 10+ years of experience with commercial and residential plumbing jobs. He’s knowledgable in all areas of plumbing including leak detection, sump pumps, water heaters, and high efficiency plumbing solutions.

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