Why do some plumbers not like tankless water heaters?
Three reasons, and none of them is that the technology is bad. The retrofit is expensive. A gas conversion often needs a larger gas line and new venting. The maintenance is real and gets skipped. The heat exchanger needs periodic descaling. And in hard water like ours, a neglected tankless unit fails early and the plumber is the one who gets the call.
1. The install is where the money goes, and clients blame the plumber for it
A gas tankless unit burns considerably more gas at peak than the tank it replaces, so a conversion frequently needs a larger-diameter gas line back toward the meter plus its own venting. A homeowner who priced the unit online and got a quote several times higher assumes they’re being gouged. They usually aren’t, but explaining that on every job wears thin, and some plumbers simply stop offering it.
2. The maintenance isn’t optional and almost nobody does it
This is the local part. Valley water deposits scale. A tankless unit pushes water through a narrow heat exchanger, which is precisely the geometry scale punishes. Manufacturers specify periodic flushing with a descaling solution. In this water that instruction is load-bearing, and the unit that was never flushed comes back as a warranty argument.
3. Diagnosing them is harder
A tank heater has a handful of failure modes and most plumbers can read them from the floor. Tankless units are electronics, sensors, flow switches and manufacturer-specific error codes, often requiring brand training and brand parts. A plumber who does two a year is slower and less certain on them than one who does two a week, and knows it.
The honest other side
Plenty of plumbers install them happily, and tankless genuinely wins for larger households that run out of hot water, for anyone reclaiming a garage bay or closet, and for owners staying long enough to earn back the install. The service life is longer than a tank's. And a tankless heater doesn’t sit on your floor holding fifty gallons waiting to fail.
How to decide without being sold
Ask for the tank replacement and the tankless conversion priced separately, as whole jobs including gas and vent work. Ask what the descaling interval is for the specific unit and what that service costs. Then decide on a day when you have hot water, not standing in a wet garage, which is when this upgrade is most often sold.
Descaling intervals are per manufacturer specification and vary by unit.
Where this page cites a utility, permit or housing figure for a specific town, it’s that town’s published data. Your own city’s water report applies to your tap and your city’s building department sets your permit rules; ask us which apply to your address.
The next thing you were going to ask.
Endless hot water and a longer life: against a higher install cost and mandatory descaling.
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