HomeBlogBlogWhy Plumbers Sometimes Advise Against Tankless Heaters

Why Plumbers Sometimes Advise Against Tankless Heaters

Why do plumbers not recommend tankless water heaters?

Plumbers don’t automatically dislike tankless water heaters, but some recommend against them when the home’s plumbing, gas supply, water quality, or usage patterns make a tank unit more reliable or less expensive to own. Tankless systems can be excellent in the right setup—yet they’re less forgiving when conditions aren’t ideal.

Upfront installation can be complicated and costly

A tankless heater often needs upgrades that a traditional tank may not: larger gas lines, dedicated venting, condensate drainage (for condensing models), and sometimes electrical work. If a home wasn’t designed for those requirements, the total installed cost can rise quickly, which is why many plumbers steer customers toward simpler replacements.

Performance depends on sizing and real-world demand

Tankless units are rated by flow rate at a given temperature rise. If multiple showers, a dishwasher, and laundry run at once, an undersized unit can deliver lukewarm water or reduced flow. Plumbers may recommend a tank when a household’s peak demand is high or unpredictable, or they may suggest careful sizing using real usage patterns.

Hard water can shorten lifespan without maintenance

Mineral buildup in the heat exchanger is a common issue, especially in areas with hard water. Without routine flushing and (often) a scale-inhibiting setup, efficiency drops and components wear faster. Some plumbers avoid recommending tankless when homeowners want “set it and forget it” equipment.

Repairs can be more specialized

Tankless heaters use sensors, control boards, modulating burners, and tighter tolerances. When something fails, troubleshooting may require manufacturer-specific parts and trained service, sometimes leading to longer downtime or higher repair costs than a basic tank heater.

For a deeper look at choosing the right size and understanding specs like GPM and BTU, see this guide: 5.28 GPM 132k BTU Indoor Gas Tankless Water Heater Guide.

FAQ

Do tankless water heaters save money over time?

They can, especially with lower standby heat loss and efficient operation, but savings depend on fuel prices, installation upgrades, and maintenance. Homes with light-to-moderate hot water use tend to see better payback.