Why Your Tankless Water Heater Isn't Heating

Tankless water heaters are supposed to provide you with constant hot water and it can be frustrating when they don't. Getting a blast of cold water in the shower or finding only lukewarm water when washing dishes is not what you need or want.

Sometimes the problem is caused by a simple issue with a simple fix. Other times, the fix is more complicated and requires more detective work. If you're dealing with cold water from your tankless heater, check out these potential causes.

Too Much Demand, Too Small a Supply

A very likely cause of cold water coming from a tankless heater is that there's just not enough hot water in the system. Tankless heaters can pass only so much water through each second, and while the heater may be working well, if you've got competing showers and faucets and appliances all trying to get that hot water, one or more of them is going to lose.

There will still be water coming through each fixture, but you're not going to get hot water through all of them. You'll get warm to cool to even cold water. It's just a matter of demand and supply. So, in this case, you'd increase the supply. Get another tankless heater installed that's dedicated to a specific appliance, for example, or one that's going to be used solely for a certain part of the house.

If you can provide the supply of hot water, you should see your problem disappear. If it doesn't, there are a couple of other things that could be going on.

Too Low a Flow, Too Old a Heater

Tankless water heaters have been around for decades. Like other appliances, the technology has improved a lot over the years.

Water heaters can last a while, and it's possible your home your home’s water heater model is older than you realize. If that's the case, then replacing your water heater with a newer, more efficient model can help your home maintain consistent hot water.

Older water heaters are more prone to lower or insufficient flow, so they typically produce less hot water. If you had low water pressure or a conservation-minded plumbing system that required only a small amount of water to flow through each fixture, the tankless heater would produce less heat.

Newer models aren't like that anymore, so the fix here is to upgrade your tankless water heater to a new model that can heat water well even when dealing with low-flow plumbing fixtures and lower water pressure.

Too Long a Pipe, Too Quick to Cool

When the heated water leaves the tank, it travels through pipes to the fixture where you need the water, such as a showerhead. The pipes, even if well-insulated, aren't usually perfect at retaining heat. When you use a faucet or showerhead and turn off the water, the water supply doesn't suddenly shrink back toward the heater; it sits in the pipes, waiting for you to turn on the water again.

As it sits, it loses that heat. This is why you get that initial blast of cool water even when your water heater is working well. If the pipes leading from the tankless heater are 50 feet or longer, then you're going to have a lot of cool water flowing through the fixture before you get anything close to warm.

And the distance could be enough to make even newly heated water cool down along the way. You end up with lukewarm water at best. Installing a recirculating pump to give that waiting water a trip back to the heater. You'd start the pump first and wait for it to shut off before using the fixture, which should take only a short time.

If your tankless water heater still isn't giving you the hot water you wanted, turn to the water heater experts at Efficient Water Heaters Inc. Give us a call now to schedule a service and get that hot water flowing as it should.