Annual Tankless Water Heater Flush

Per Apple Reminders, it is time for the annual tankless water heater flush for both tankless water heaters for the house. For those of you who have tanked water heaters or already know how to flush your tankless water heater, feel free to ignore. For those of you who pay someone a lot of money or are considering a tankless hot water heater (buying or building a home with one or retrofitting) and wonder what is actually involved, this is the thread for you. My tankless water heaters are a Noritz; others may have a slightly different process, although the idea is similar no matter the brand.

Since I was going to use the wagon for the first time in a while, it was a good opportunity to inflate the tires.

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For the tankless heater flush, I have a tankless flush kit that includes a couple of hoses, a bucket, and sump pump; it is up to you if you want to buy a kit like this or piece the kit yourself. You can use Vinegar, CLR, or other tankless heater flush solution; this time I'm using Haymaker Tankless Water Heater Descaler. I also take a screwdriver (in this case the Milwaukee M12 Screwdriver) with a Philips tip or bit. The reason for hauling the Ego battery generator is because I don't have an outlet near the west Tankless water heater, which I need to fix another day.

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Before taking the cover off and switching the mode, you should turn the power off to the tankless heater. My tankless heaters do have a switch near it; others tell me that they don't have a switch and have to flip a breaker, which is less convenient. The directions to swap to flush mode are conveniently inside the inner cover over the harness that I need to connect. Before removing the tank cover, it is a good time to clean up mud dauber nests.

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Be sure to connect the hoses, fill the bucket, shut off water to and from the tankless heater, and open up the service ports before swapping the heater to flush mode and powering back up.

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For my tankless heater, this blue plug unplugged is normal mode; plugged in is flush mode.

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When powered on again, my panel's LCD display shows "CCC" and then shows "C" with a number starting at 60 and counts down to 0 showing where the countdown is in minutes; Noritz has a 60 minute flush cycle. When the flush begins, confirm that you have water flowing through the pump, into the bucket, and from the pump into the tankless heater. This is also a good time to empty the contents of the flush solution into the bucket. Most of the solutions that I've used require 1 quart container per 1 gallon or so of water; you want enough water to make the pump to work without burning up.

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After an hour, depending on what you use, the liquid may change from a color to clear or from clear to a color; your miles may vary. You can also see some other junk in there, which is normal for the flush process.

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After the 60 minutes of flushing, then it is time to run 3 minutes of clean water; just turn off the valve for the cold water side service port and open up the cold water valve to the tankless heater for clean water. After flushing for 3 minutes, turn the tankless water off, take it out of flush mode, remove hoses, and make sure that both hot and cold water valves are open before you turn the tankless heater on and put the covers back on.

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For the west side of the house, I did use the Ego generator, and with a couple of 5Ah batteries that weren't fully charged to begin with, it has enough power to run the pump for a full hour or so. If you don't have an outlet that is convenient, run an extension cord; I just prefer to test out the generator and confirm the health of my batteries in case I need to use it in an emergency. So far, it seems that my parents end up needing to use it more than I do.

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Thanks for sharing this with us! :ThumbsUp

UUGGGGGHHHHHHH. I have only done mine once in 20 years. It's been in the back of my mind to open this can of worms but I'm waiting now till it warms up a bit. Maybe summer.

About 5 years ago, the kids had issues where there was enough mineral buildup where low water flow affected their ability to receive hot water in their showers, although this was mostly in the summer. After some research, in addition to other improvements, it turns out that I'm supposed to flush these tankless water heaters more often because of the nature of the on-demand heating and smaller, narrow heat-exchange coils makes them more susceptible to mineral buildup that shows up more quickly on tankless water heaters over tanked water heaters. The things that show up on a tanked water heater in 10-20 years maintenance show up on a tankless in 2-3 years without maintenance.

The older homes in the first phase of our neighborhood (maybe close to 20 years old) still have tanked water heaters, while all of the new construction have tankless. Both have their pros and cons, since I've had a couple of houses prior to this one with tanked heaters. I never flushed my tanked heaters, even though I should also decalcify them, so I was oblivious to the tankless maintenance. It was in the mid to high 70's this weekend, so it was actually good to knock out all of monthly and seasonal tasks around the house before heading out of town, although it is taking away the time that I need to make my boat usable again.

So why bother heating hot water anyway? lol

Fixed the redundancy since it's my forum and can edit. :biggrin