Since tankless water heaters don't store water like tank models do, the risk of a leak is lower. However, even though leaks aren't common in tankless heaters, it's still possible for a leak to develop. Here are some reasons a tankless water heater might leak and the repairs that might be needed.
Reasons A Tankless Water Heater Starts Leaking
If your water heater is leaking, the problem might be in the pipe connections rather than a serious problem with the tank. When you call a plumber to make repairs, the first thing they may check is the connections leading to the water heater. If a thread is crooked or a connection is loose, water can drip down the pipe and along the heater until it drips on your floor.
If your tankless heater is indoors, or in an area where water could cause a lot of damage, it's a good practice to put a drip pan below the heater to catch water if a leak ever develops. Leaking might never be a problem, but if it is, water will collect in the pan and save you from the expense of repairing water damage.
Another reason a tankless water heater can leak is due to corrosion. Corrosion might happen if you have hard or acidic water that eats pinholes in the coils. Corrosion to the heat exchanger might also happen if you have a tankless gas heater that isn't vented properly.
Water Heater Repairs You Might Need
The water heater repairs you need might be simple. If a connection is loose, the plumber can tighten it and that will stop the leak. The plumber might also recommend flushing the heater if you haven't done so recently to get rid of hard water scale buildup.
The plumber might also check the pH of your water to see if acidity is a problem. Hard water can be corrected with a water softener, and the pH can be raised by adding a neutralizer filter if needed. If you have well water, check your water tests to see if hard or acidic water might be a problem for your water heater and plumbing in general.
Coils that are already in bad shape from corrosion are a more serious problem and may require more extensive repairs. Repairs might be possible, but your plumber might also recommend replacing the entire heater.
If your heater started leaking due to a corroded heat exchanger years before the end of the heater's expected lifespan, it's worth tracking down the problem so you understand what happened and so you can keep the same thing from happening with your new heater.