Tankless water heater service

Before you call: collect these

• Brand and full model number (on the side label or inside the cover sticker — don't open the cover).
• The exact error code shown on the display or remote, and when it appears.
• Fuel: natural gas, propane, or electric.
• Whether a maintenance flush has ever been done, and when.
• Whether recent work was done on gas lines, venting or plumbing.

Flow-dependent problems

Tankless heaters fire only when water flows above a minimum rate. That creates some behaviors that aren't defects:

• Cold at a trickle — a very low flow may not trigger the burner.
• Cold sandwich — a brief burst of cold between uses.
• Fluctuating temperature with several fixtures open — demand can exceed what the unit can heat.

Other patterns — the unit shutting down mid-shower, repeated ignition codes, reduced flow at every faucet — more often call for service. Scale in the heat exchanger, a clogged inlet filter, venting faults or gas supply sizing are among the things a technician evaluates.

Maintenance depends on the model

Manufacturers publish their own descaling and filter-cleaning guidance, and it varies by model and by water quality. We don't recommend a single interval for everyone. Check your owner's manual or the manufacturer's website, and ask the contractor what schedule they suggest for your supply — city water or a private well. More in our maintenance guide.

Repair, warranty and parts

Tankless parts are model-specific. Ask whether the contractor services your brand and can source parts, and check warranty registration — some warranties require documented maintenance or installation by a qualified installer.

Planning prices for this job