Tankless water heaters can save you a lot of money by reducing the electricity or gas spent to keep water hot that's just sitting in a holding tank. However, since these units are typically installed inside the rooms of the home instead of in a basement or crawlspace, it's common for homeowners to become concerned about the noises they're hearing from the equipment. Find out what noises are normal and which ones indicate potential problems.
As long as the clicking is not continuous, it's perfectly normal to hear this noise from a functioning tankless water heater. An audible clicking noise is produced by the flow switch inside the unit which is responsible for controlling how much water comes in and out. If you hear clicking constantly when there's no demand on the hot water, you may have a damaged switch that needs replacement.
Does your tankless water heater seem to moan or groan every time you use an appliance near it that only draws cold water? This indicates a broken check valve, which is creating a vacuum problem with your plumbing. Cold water appliances are not supposed to draw water from a heater unit, but it can happen anyway when the check valve is no longer controlling proper flow. You may hear the noise coming from the pipes leading in and out of the unit instead of from the heater itself.
Many people who install gas heaters are surprised at just how loud the ignition sequence is when you first turn on the hot water tap. In fact, it's not abnormal for some models to get as loud as 90 decibels before settling back down. That's nearly as loud as a jackhammer being operated just 50 feet away from you. Installing the unit inside an insulated box can cut down dramatically on the volume it produces. Constant rumbling is not normal, and a tankless water heater that won't stop rumbling should be switched off until it can be inspected.
It might sound like there's a tiny gnome trapped inside the heater who's knocking on the walls, but it's likely not coming from the water heater at all. If you notice knocking or banging when using the water heater or shortly after you stop using it, it's most likely your pipes either banging against part of the home's structure or a phenomenon known as water hammer. The sound travels through the pipes and water and can echo in the heater. Depending on which problem is the cause, it's an easy fix with either straps to stabilize the pipes or a simple device to absorb the shock that causes water hammer. Visit http://www.firstclassplumbinginc.com for more information.