A leaking tankless water heater is sometomes caused by a loose plumbing connection,  a bad Oring a damaged or faulty pressure relief valve on the tank, or tankless system, and even  internal corrosion from hard water buid up over the years.

Steps to stop the leaks would be to include turning off the main water supply and power to the water heater.  Identifying if the leak is from the unit or piping, and checking for water buildup condensation.

Common  reasons for Tankless water heat Leaks are, Loose Connections,, Thermal expansion can loosen the plumbing pipes, joints, connections or fittings may not be tight.

Pressure Relief Valve (T&P Valve): If the valve is failing or if the water pressure is too high, it may drip. It should not be capped off. Condensation: In high-efficiency units, the condensate line might be blocked, causing water to back up. Heat Exchanger Corrosion: Hard water can corrode the heat exchanger, which often requires a full unit replacement rather than repair. Improper Installation: Improperly installed venting or pipe fittings can cause leaks. If your water heater isn't working, the first step is to identify whether you have a gas or electric model, as the causes and fixes differ significantly. Electric Water Heater Troubleshooting Check the Circuit Breaker: Look for a tripped breaker in your home's main electrical panel. If it's tripped, flip it fully to "OFF" and then back to "ON". Press the Reset Button: Most electric models have a red high-temperature limit switch (reset button) located behind the top access panel. Note: Always turn off the breaker before removing the panel for safety. Test the Heating Elements: If the breaker and reset button are fine, a heating