How to Flush your Tankless Water Heater!

How to Flush

your Tankless Water Heater

by Alex Watts, proprietor of Dream Home Amelia, LLC

(FL Home Inspector license #: HI16077; FL Real Estate license #: SL3358062)

Congratulations! Your home is equipped with a Tankless Water Heater! You have the joys of endless hot water, you save the space of housing a large 40+ gallon tank, and heating your water is more efficient and costs less! With proper annual maintenance a Tankless can last 25 years, as opposed to the 12-year lifespan of the tanked variety!

Manufacturers recommend a de-scaling flush be performed annually. You can do this task yourself, or you can hire Dream Home Amelia to do it for you! As you can imagine, performing your own de-scaling flush is one of the hardest jobs known to mankind. About 60 million people die every year.* As long as you have the proper supplies, though, you are probably quite capable of both completing and surviving the Tankless flush. It is a dangerous, messy, and draining job. From beginning to end I’ll describe the safest process to de-scale your Tankless, and hopefully provide you with the knowledge to just forget it and hire DHA.

First and foremost, you will want to obtain your supplies. This process may differ, but here is basically how I get my supplies:

Step 1 – Steal your ex’s credit card & head to Home Depot. It’s gonna be a good day.

Step 2 – Pick up the necessary items:

     I. 1/6 HP submersible pump ($96.00)

II. ¾” hose set ($26.98)

III. 100-ft electric cord ($19.98)

     Uhh, Four. Two five-gallon buckets ($8.96)

     V. Wrench/pliers ($5.97)

VI. 1-gallon distilled white vinegar ($3.74)

     VII. 1-gallon distilled water ($1.22)

Step 3 – Approach your Tankless carefully – you don’t want to startle it.

Step 4 – Operate the electrical disconnect (turn the power off to the unit). If your unit utilizes propane gas, turn the gas shutoff valve to the ‘off’ position.

Step 5 – Close the cold-water inlet valve. Close the hot-water outlet valve.

Step 6 – Unscrew the isolation valve covers. Open both isolation valves.

Step 7 – Allow the unit to drain while you plug your electrical cord into an outlet.

Step 8 – Connect your hoses to the isolation valves. The other end of the inlet hose is connected to the submersible pump’s discharge bib. The other end of the outlet hose is placed into the bucket containing the pump. Fill this bucket with the vinegar solution.

Step 9 – Connect the power to the submersible pump & watch as the outlet hose begins to discharge the vinegar solution into the bucket. The submersible pump recirculates the solution through the unit. You’ll want to run this flush for an hour.

Step 9.5 – Now that the vinegar solution is circulating, you may choose to remove the front cover to inspect the control unit, blower fan, insect & pest detritus, and to gauge the general condition of the Tankless. Replace the cover.

Step 10 – At the Halfway point unplug the power to the pump, pausing the  flush. Very carefully remove the inlet screen and check it for debris. Clean and replace the inlet screen. Return power to the pump to continue the flush.

Step 11 – When it’s been an hour, power down the submersible pump. Pick it up, letting the vinegar solution drain out of the pump and unit. Place the pump & outlet hose end into the other bucket. Fill this bucket with distilled water.
Step 12 – Reconnect power to the submersible pump and allow the distilled water to run through the unit for five minutes.

Step 13 – Disconnect the pump and hoses. Close both isolation valves. Replace both isolation valve covers.

Step 14 – Open the cold-water inlet valve. Open the hot-water outlet valve. Turn the propane gas valve back to the ‘on’ position & reconnect the unit’s electrical disconnect returning power to the unit.

Depending on your Tankless model, the control module may beep and/or need to be reset. Consult your unit’s manual (or check YouTube). I recommend setting your hot water no higher than 120 degrees Fahrenheit. The bucket of water can be dumped mostly anywhere. Do not dump the vinegar bucket on the lawn, unless, like me, you wonder if it kills grass. It does. Find a discreet location to dump the vinegar or pour it down a drain with running water. The vinegar solution is non-toxic, but dilution will help it flow with less odor.

As with any project there are nuances and additional factors involved for which only education & experience can properly prepare you. This has been a fair description of the Tankless de-scaling process, but I didn’t mention such things as hose bushings/gaskets, thread tape, gas-metering, how to open the cover, check the blower, etc… because each Tankless system is going to come with its own peculiarities. Even though flushing the built-up limescale from your Tankless is pretty straightforward, if you do tackle it yourself, you’ll spend $174.25 just for the supplies, then you’ll have to store the pump, hoses, & buckets, while hoping the pump still works next year.

Whereas Dream Home Amelia charges just $69.99, has the expertise & experience to professionally perform the service, removes the hassle from you completely, and provides a valuable source of information about your house’s structure (I am a licensed home inspector), about the area (I came up in Fernandina), and about outer space (because I like astrophysics and aliens).

So, choose Dream Home Amelia to de-scale your Tankless, perform your own system’s annual flush, or don’t do it at all (with our area’s hard water a Tankless will last 5-6 years without flushing, then kaput!).

Thank you for choosing Dream Home Amelia!

Alex Watts

(904) 581-7812


Dream Home Amelia of Northeast Florida

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