To maintain optimal performance and longevity, most manufacturers and plumbers suggest flushing a propane tankless water heater at least once annually. Mineral buildup accumulates faster inside systems with hard water. Professionals usually recommend flushing the system every six to nine months if you have hard water.
Signs Your Tankless Water Heater Needs Flushing
Watch for these indicators: Fluctuating water temperatures – If your hot water suddenly becomes inconsistent, mineral buildup may be affecting the heat exchanger. Reduced water pressure – Scale can clog the pipes, leading to lower water pressure throughout your home.
Check with a local pro for your specific job. Cost Insights: Tank water heater flushing costs $110 to $200, while tankless models run $150 to $250 due to their more complex components. Your tank size and household hot-water use affect flush time, since larger tanks take longer to drain and refill.
A tankless water heater cannot provide hot water faster than its ability to heat the water. While a tank unit can provide hot water for multiple uses at once, a tankless unit might not be able to support simultaneous usage, such as washing dishes, taking a shower and running a washing machine all at once.
Open the purge port valves by twisting them perpendicular to the position of the cold and hot valves. 7. Use 4 gallons (15.1 liters) of undiluted white vinegar to clean your tankless water heater. Never use chemical solutions of any kind.
If a standard showerhead is fitted, it will use around an extra half a gallon each minute, accounting for a 25-gallon emittance every 10 minutes, or 50 gallons throughout a 20-minute shower. *1 gallon = 4.54 litres.
Here are some common reasons why your tankless water heater might not be working and how you can troubleshoot these problems.
For larger households, multiple showers, laundry, and dishwashing may run at the same time. Hot water demand could reach 10–12+ GPM. A high-capacity tankless water heater—or even two units installed in parallel—may be the best solution.
Gas tankless water heaters installed by December 25, 2025, might qualify for a $600 federal tax credit. The government is offered this 30% credit through December 2025 to help cover the cost of the unit and its installation. This tax credit comes from the 25C Energy Efficient Home Improvement Tax Credit program.
Showers & Bathtubs
The average shower uses about 2 gallons of water per minute. If there are four people in your household and each person takes a 10-minute shower daily, that's 80 gallons of water.
Flushing tankless water heaters whose heat exchangers are blocked by the lime scale is very important and must be done before something happens. If you don't flush the water heater, the heat exchanger can be damaged as not enough water will pass through and cool it down.
I've used it once a year, every year - so ten time (both water heaters once a year). I haven't had any issues. Each tank is flushed for 45 minutes with two gallons of vinegar (separate two gallons of new vinegar used for each tankless heater).
In short, draining removes water. Flushing removes sediment, and that makes all the difference.
Water main flushing is the process of cleaning the interior of water mains and removing any accumulated sediment by sending a rapid flow of water through the mains. This rapid flow disrupts any sediment that may accumulate in the main over time, allowing us to filter and remove it.
Tankless water heaters might produce cold water due to low water flow, mineral deposits, incorrect installation, or insufficient system capacity. Addressing these issues through regular maintenance, professional repairs, or system replacement can ensure a steady hot water supply.
Drawbacks of Tankless Water Heaters
As discussed above, the biggest downside of owning a tankless water heater is its higher cost. The initial installation and unit costs are more expensive than a traditional storage-tank water heater.
In freezing temperatures, condensate produced by a condensing tankless hot water heater can freeze inside the drain line, which can cause leakage, operation issues or shutoff. To help keep your indoor tankless water heater from freezing, use a direct vent exhaust & intake system.
A gas tankless water heater (natural gas) is only marginally cheaper to operate than an electric tankless water heater due to the exceptionally high thermal efficiencies of the electric units (99%+).
A 250-gallon propane tank holds roughly 200 usable gallons (due to the 80% fill rule). Depending on your appliance load: Light use (stove, water heater only): 6–10 months. Moderate use (heat + cooking + water): 2–4 months in winter.
Tankless water heaters require more gas or electric power than tank type water heaters. They save energy by operating only when there is demand for hot water. This results in larger gas pipes and larger electric circuits. For a new building design, this may not be a problem.
This problem usually comes down to capacity, heat production, or mixing issues inside your plumbing system. Sometimes the fix is simple, like adjusting your water heater temperature or flushing out sediment. Other times you may need a new mixing valve, an element replacement, or a different size water heater.
Here is a simple way to decide: Choose Navien if you want the highest efficiency, longest warranty, and built-in recirculation. Choose Rinnai if you have a large household and need the highest flow rates. Choose Rheem if you want a reliable brand at a lower price point.