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All hustles  /  You buy the kit  /  Tankless Water Heater Flushing

Tankless Water Heater Flushing

Descaling tankless water heaters for homeowners on an annual cycle, charging a flat rate per unit for about ninety minutes of work with a pump, two hoses and a bucket of descaler.

One job pays
$189
one descaling flush of one accessible tankless water heater that already has service valves
Out of that
$20 to $50
Descaling solution for one flush
Time on the job
60 to 90 minutes on site, the operator's flat rate covers up to 90 minutes of labour, of which 45 to 60 minutes is the solution circulating while you are present but not working hard
Unpaid time
About 40 minutes per job: round-trip drive across a suburban service area, the phone call that qualifies whether the unit has service valves, and the share of calls that turn out to have none and have to be handed off
Jobs in a week
5 to 10 part-time, since each job is about ninety minutes on site plus travel and they cluster badly around evenings and Saturdays
To start
$100 – $150
$100 to $150 for the pump, hoses, bucket and first batch of descaling solution, before insurance and any state business registration
First money in
One to three weeks
One to three weeks, the kit ships in days and the job itself is about two hours the first time, so the gating item is the answer from your state board, not the equipment

That is 2.1 times BLS median hourly wage for plumbers, pipefitters and steamfitters, the trade this work is carved out of, $31 an hour.

What the job actually is

A tankless water heater heats water by running it across a heat exchanger, and in hard water that exchanger slowly fills with mineral scale until the unit underperforms or throws an error code. Flushing is the routine fix: you connect hoses to the two service valves already on the unit, circulate a descaling solution through it with a small submersible pump, then rinse it with fresh water. Manufacturers recommend it annually, so one customer won is a customer who needs you again next year.

How the work goes

  1. 1

    Isolate the unit

    Shut off the gas or power and close the hot and cold shutoffs, leaving the unit sealed off from the house supply.

  2. 2

    Connect to the existing service valves

    Attach a washing-machine hose from the cold service port to the pump sitting in a five-gallon bucket, and a return hose from the hot service port back into the same bucket.

  3. 3

    Circulate the descaler

    Fill the bucket with white vinegar or an approved descaling solution and run the pump so it loops through the heat exchanger. Navien specifies at least 45 minutes of circulation.

  4. 4

    Rinse with fresh water

    Drain the solution, then flush clean water through the unit for at least ten minutes so no acid is left in the exchanger.

  5. 5

    Clean the inlet filter screen

    Pull and rinse the cold-water inlet screen, which traps grit and is a common cause of low flow complaints.

  6. 6

    Restore, test and book the next one

    Reopen the valves, relight or repower, run a hot tap to confirm temperature and check for error codes, then put next year's flush in the calendar.

How to get your first paid job

  1. 1

    Phone your state's plumbing or contractor board before you buy anything

    Ask the specific question: may an unlicensed person take a sub-$1,000 maintenance job flushing a homeowner's tankless water heater through its existing service valves? Arizona, Florida and California have minor-work exemptions a $189 job fits inside; Texas treats water heater service as licensed plumbing, so if that is your answer, stop here and look at working under a licensed plumber instead.

  2. 2

    Buy the kit and learn on your own unit

    A pump, two double-female hoses, a five-gallon bucket and descaler run about $100 to $150. Run the full procedure on your own or a friend's heater first, 45 minutes circulating, 10 minutes rinsing, so the first paid job is your third flush, not your first.

  3. 3

    Write the qualifying script before you advertise

    One question decides whether a job is yours: does the heater have two small valves with caps on the pipes underneath? Yes means a flat-rate flush. No means a referral to a plumber, and worth asking that plumber for a referral fee.

  4. 4

    Get the first customers street by street, not on a lead platform

    Post in Nextdoor groups for neighbourhoods built or retrofitted in the last fifteen years, and leave door hangers on streets where you can see tankless units on exterior walls. Lead in with the error code and the lukewarm-shower complaint, not with the word descaling, and where your exemption requires it, put 'not a licensed contractor' on the hanger.

  5. 5

    Price one flat rate and hold it

    Publish a single figure for an accessible unit, in the $169 to $189 band the operators use, and charge the indoor or awkward-access premium separately. A flat price is what lets you quote on the phone in a minute instead of driving out to estimate.

  6. 6

    Book next year's flush before you leave

    Manufacturers recommend descaling at least annually, and Rinnai-style warranties exclude scale damage, so the renewal is an easy conversation while you are standing next to the unit. Put the date in the calendar on site and the second year sells itself.

The catch

The thing to get right is the legal category of the work in your own state, and it is a phone call to the board, not a judgement call. Arizona exempts casual or minor work under $1,000 and Florida under $2,500, so a $189 flush sits comfortably inside the exemption; Texas instead defines servicing a water-circulating appliance as plumbing and expressly refuses the appliance-dealer exemption for water heaters, so there the licence comes first. The second thing, and the one that protects you everywhere, is to only ever work through service valves already fitted to the unit, qualify every caller by asking whether the heater has two small valves with caps underneath, and hand the ones without to a licensed plumber, because fitting them is pipework rather than maintenance: the operator who prices both charges $350 with a bypass present and $695 when a new one has to be installed.

What you need to buy

  • Tankless water heater flush kit (pump, hoses, bucket, descaler)

    The whole job in one box, the cheapest route in, and the item every single person doing this has to buy

    Find one

  • Submersible utility pump, 1/6 to 1/3 HP

    Circulates the descaling solution through the heat exchanger; the part that actually does the work and the one worth upgrading first

    Find one

  • Descaling solution, food-grade or manufacturer-approved

    The consumable on every job. Navien permits plain white vinegar, which is the cheap alternative when a customer's warranty terms allow it

    Find one

  • Double-female washing machine hoses, stainless braided

    Connect the pump and the return line to the unit's service valves; Navien specifies a double-ended washing machine hose

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  • Five-gallon bucket

    Holds the solution and catches the return; the manufacturer procedure is written around a 5-gallon pail

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  • Water hardness test strips

    Turns the sales conversation into a measurement, a strip reading above 180 mg/L is USGS 'very hard', which is the argument for a shorter service interval and the annual rebooking

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Where to sign up

Before you start

  • A direct answer from your own state's plumbing or contractor board on whether an unlicensed person may take a sub-threshold appliance maintenance job for a homeowner, this decides whether the hustle is open to you at all
  • A flush kit: submersible utility pump, two double-female hoses, a five-gallon bucket, and descaling solution
  • Basic plumbing confidence, Navien says descaling it yourself requires at least basic plumbing experience
  • A vehicle that can carry a bucket, a pump and hoses
  • In states that allow it under a minor-work exemption, advertising that discloses you are not a licensed contractor, Arizona requires the words 'not a licensed contractor' in the advert itself
  • General liability insurance, because you are circulating acid through someone else's appliance