No tank means no tank failure — but tankless water heaters absolutely still leak. They just do it from their own exclusive list of weak points: condensate plumbing, service valves, heat exchanger seals, and fittings. The good news for the maintenance-minded: nearly all of these trace back to service intervals, which means nearly all of them are preventable.
Our take, honed from years of Wheaton service calls: understand it, watch for it, and build the habit around it.
Drain line problems
High-efficiency condensing units produce acidic condensate that must drain away continuously. When that little drain line clogs with slime or sediment, water backs up into the cabinet — and suddenly there's a 'leak' that's really a drainage failure.
The habit: check the condensate line during service, keep it clear, and make sure it terminates where it should. It's a two-minute check that prevents one of the most common tankless water-intrusion calls we run.
Service valve leaks
Tankless units have isolation valves specifically so the unit can be serviced and descaled without draining the house. The irony: valves that sit untouched between services can weep when finally operated — or develop slow seeps at their seals from years of disuse.
Exercising these valves during scheduled service keeps them honest. If yours haven't moved in years and you're due for descaling anyway, mention it — we'll treat them gently and replace any that have given up.
Failed exchanger seals
The heat exchanger is the heart of the unit — and its seals live the hardest life, cycling between hot and cold constantly. Scale buildup makes it worse: an insulated, overheating exchanger stresses every seal and joint around it.
This is where the descaling habit earns its keep. Regular descaling matched to your water hardness keeps the exchanger clean, temperatures normal, and seals living their full life instead of a shortened one.
Fitting and connection leaks
Water in, water out, gas in, condensate out — a tankless unit has more connections per square foot than a tank heater, and each one is a potential weep point. Vibration, thermal cycling, and time do the rest.
The seasonal glance applies here too: look at the unit's connections now and then, note any mineral crust or dampness, and don't ignore the cabinet floor. Tankless leaks often announce themselves quietly before they announce themselves loudly.
Tankless: a different diagnosis
Tankless units talk: error codes, diagnostic displays, and service history narrow the search fast. We combine what the unit reports with a hands-on inspection of condensate flow, valve condition, and seal integrity.
It's a different detective process than a tank heater — less 'trace the rust trail,' more 'read the unit, verify with eyes and hands.' The result is the same: the true source found, not just the wettest spot patched.
The maintenance that prevents tankless leaks
The tankless prevention list is short and specific: descale on schedule for your water hardness, keep the condensate line clear, exercise isolation valves during service, and glance at connections seasonally. That's genuinely most of it.
Put the descaling on a calendar reminder and the rest follows naturally during the service visit. Tankless units reward routine lavishly — and punish neglect just as reliably as any tank.
Your maintenance takeaway
Tankless leaks are rarely mysteries and almost never bad luck — they're maintenance items with consequences. Keep the descaling schedule, mind the condensate line, and your unit stays dry. Need a service or chasing a drip? Call (833) 713-2101.