A tankless hot water heater is a good option for businesses that need intermittent hot water for a restroom or other locations where it is used only occasionally. Their efficiency and point-of-use capability keeps energy costs lower as compared to traditional tank units. However, tankless water heaters require annual maintenance to operate at maximum efficiency and to avoid cutting their lifespans short. Below is why tankless water heaters need to be regularly flushed and how you can perform this important task:
Why tankless hot water heaters need flushing
Despite being clear, all tap water contains sediment to some degree. Sediments commonly found in drinking water include magnesium and calcium as well as other elements. As water is heated, these sediments will coalesce on the interior plumbing of the hot water heater and form scale.
A small amount of scale won't cause any trouble, but as the scale layer gets thicker, the tankless water heater has to work harder to heat the water to its necessary temperature. In addition, water flow is reduced for the user, which can be inconvenient and frustrating. Finally, increased heat loads can cause components to wear out prematurely and fail.
Fortunately, flushing the plumbing inside a tankless water heater with a weak acid, such as white vinegar, will dissolve the troublesome scale. It is an easy and low-cost job, and almost anyone can do it. Below is a list of materials you need and step-by-step instructions:
What you will need
One-gallon jugs of white vinegar, quantity of 3
Washing machine hoses with female fittings, quantity of 2
Submersible water pump with male hose fitting on outlet, ½ horsepower
1. Shut off the tankless water heater and drain any remaining water - Shut the unit off following the manufacturer's directions, and allow it to sit undisturbed for half an hour to be sure it has cooled down completely. Next, attach washing machine hoses to the service valves located on the cold water inlet and hot water outlet, and place the free end of the hose connected to the hot water side into an empty five-gallon bucket. Turn the valve handles on the cold and hot water valves to the 'off' position; you will know they are off when aligned perpendicular to the water lines. Finally, turn the service valve drain handle on the hot water valve to allow water inside the tank to flow freely from the tank into the bucket. Once the water flow slows to a drip, you are ready to move to the next step.
2. Attach the submersible pump to the tankless water heater and begin flushing - After you have drained all the residual water inside the unit, empty the water from the bucket. Place the end of the hose leading from the hot water service valve back into the bucket. Next, attach the free end of the hose connected to the cold water valve to the outlet of the submersible pump. Carefully lower the pump into the bucket and rest it on the bottom. Be sure it is resting in a stable position and that you have plenty of working room between the pump and water heater.
Once the pump is in position, pour three gallons of white vinegar inside the bucket. Turn the service valve drain handle on the cold water valve to the 'on' position and double check to be sure the drain on the hot water valve is still open. Next, plug in the submersible pump; if all connections have been properly made, the pump will begin sucking vinegar into its inlet and out through the hose into the water heater through the cold water inlet. The vinegar will then circulate through the plumbing, dissolving deposits along the way, and exit through the hot water valve and into the bucket. At that point, the vinegar will be sucked back into the pump and continuously recirculated. The vinegar will maintain its potency for quite a while, so there is no need to replace it during the process.
3. Shut off the pump, disconnect the hoses and restore operation of the tankless water heater - Once you have allowed the white vinegar to circulate for at least 30 minutes, unplug the pump. Next, remove the hoses from the inlet and outlet valves and turn off the drain valve handles. Turn the main water valves on each side, hot and cold, back to their 'on' positions to restore the normal flow of water through the unit. After water is flowing back into the unit, turn on your tankless water heater and open the nearest hot water tap to drain the vinegar from the unit's plumbing. Allow the tap to run for several minutes to remove any trace of vinegar from the water heater and plumbing.
For professional advice or help with this project, contact a company like Cool Air Mechanical, Inc.