There are arguments for investing in a tankless water heater including the fact that it generates hot water only when you need it—and for as long as you need it—saving 27 to 50 percent of fuel costs over tank-type heaters. (A typical gas-fired tank wastes 40 to 50 percent of the fuel it burns.) Tankless water heaters take up much less space than storage water heaters as they heat the water directly. When you turn on the hot water, the cold water travels through a pipe and into the tankless water heater unit where it is heated by a gas burner or an electric element. This allows you a constant supply of hot water.
In this article, we’re going to discuss a few common issues that homeowners experience with their tankless water heaters. We have produced a short video highlighting some of these issues and ways to fix them below.
Tankless water heaters are energy-efficient, have low maintenance costs, and are reasonably durable. But just like any appliance, they’re not completely immune to issues. From time to time, they may present with minor problems, such as having no hot water, or not firing. Tankless water heaters, also known as demand-type or instantaneous water heaters, provide hot water only as it is needed. They don’t produce the standby energy losses associated with storage water heaters, which can save you money.
Tankless water heaters heat water directly without the use of a storage tank. When a hot water tap is turned on, cold water travels through a pipe into the unit. Either a gas burner or an electric element heats the water. As a result, tankless water heaters deliver a constant supply of hot water. You don’t need to wait for a storage tank to fill up with enough hot water. However, a tankless water heater’s output limits the flow rate.
If your tankless water heater isn’t performing up to par here’s what you should check.
What’s the issue when you have no hot water in house but have cold water? This is the most common problem you can expect with a tankless water heater. To get to the root of the problem, ask yourself the following questions.
If you’re running the dishwasher, doing a load of towels, and showering at the same time, chances are you’re just running your water heater to its limits. Every tankless water heater has a flow rate capacity that should give you a good idea of how much hot water can be used simultaneously. Choose which hot water activity you need right now, turn off the others, and restart your unit. Many times, this is just due to too many faucets being run at once, like your shower and the kitchen sink. For example, taking a shower and running the dishwasher at the same time can stretch a tankless water heater to its limit. To overcome this problem, you can install two or more tankless water heaters, connected in parallel for simultaneous demands of hot water. You can also install separate tankless water heaters for appliances — such as a clothes washer or dishwater — that use a lot of hot water in your home.
The minimum flow rate is the amount of water (in gallons) the tankless unit needs flowing through every minute to produce hot water. If you’re asking for less than the minimum flow rate, the unit is probably shutting off as a safety measure. Increase the flow out of your faucet and wait to see if the water heats up. Tankless water heaters must be able to sense water flow in order to initiate operation. Most models will operate with flow rates as low as 0.5 gallons per minute. This is the lowest minimum flow rate in the industry and is an important benefit.
Typically, tankless water heaters provide hot water at a rate of 2–5 gallons (7.6–15.2 liters) per minute. Gas-fired tankless water heaters produce higher flow rates than electric ones. Sometimes, however, even the largest, gas-fired model cannot supply enough hot water for simultaneous, multiple uses in large households.
Check your vents and air intake channels for blockages. Lucky for you, most tankless water heaters have notification systems that tell you if you have a blocked exhaust vent somewhere. Make sure everything—inside and outside—is free of blockages, dust bunnies, or other debris. Dirty burners are also a source of blockage. Make sure they’re clean!
If you’re running on electricity, check your main electrical panel. Something may have caused the breaker to trip, requiring a reset before your tankless water heater will work again. If you’re burning gas, make sure you paid your bill, there’s propane in your tank, or the gas valve is fully in the ON position.
In the winter, frozen water pipes can prevent hot water from reaching you and your appliances. Safely and naturally thaw your pipes before trying again for some hot water.
So what if you’re experiencing the opposite problem? Here are the things to fix if your water is getting too hot:
A problem specific to electrically powered water heaters is a faulty heater element. Electric water heaters may be equipped with either one or two heating elements. If a heating element begins to ground out, it will stay on all the time and overheat drastically. Not surprisingly, the result will be painfully hot water – and that’s just for starters. With time, the heater element will burn itself out completely. Then you’ll have no hot water at all until the element is replaced.
The water heater and the pipes could be susceptible to becoming blocked partially or fully due to a buildup of mineral or sediment. Systems with iron pipes and components can rust and lead to iron sediment building up throughout. Meanwhile, homes with hard water could see minerals like calcium and magnesium resulting in a scale buildup.
Over time, these minerals and sediment can become stuck in place, leading to a gradually growing buildup that narrows the passage that the water moves through. This can affect the pressure and temperature of the water and make it potentially unsafe.
If you are experiencing problems relative to buildup, you’ll need to call a professional to flush your system. This should be a part of your regular annual maintenance so as to avoid more damaging issues caused by mineral or sediment buildup.
It’s the dreaded cold water sandwich, which most often occurs in the shower. Here’s what’s probably happening: Someone in your home could have showered just before you. The hot water you’re feeling in the beginning is the leftovers from the previous person. Then, the water gets cold again while the tankless water heater is re-heating the water for your shower. Then, once the heater does its job, you get your hot water again.
If this happens a lot or really gets on your nerves, ask your Northwest Arkansas plumber if a mini tank water heater could help. A small tank will give hot water while the tankless unit heats up, preventing this cold water sandwich in the future.
A cold water sandwich effect refers to the phenomenon where the water from a heater is warm for a few minutes, then unloads a burst of cold water, and then the water quickly returns to being warm again. This is a common problem with tankless water heaters. There is some water which remains stored in warm condition at the mouth of the faucet or other outlets, which means when someone runs the tap or the shower, he will receive some hot water instantly. However, a tankless heater takes some time to heat up the exchanger and during that time, some cold water may get through the exchanger and reach the user. The issue at hand is more common to electric water heaters than it is with gas powered heaters. The reason for this is that gas reaches the operating temperature almost immediately, whereas electric heaters may take a minute or two to reach the required temperature for heating.
Your water should always be clean and clear. If it’s discolored or smells funky, you might have something like mold, fungus, or bacteria growing inside your unit. The most common bad smell you can pick out is that of “sulfur” or rotten eggs.
This smell is typically caused by sulfate bacteria that can develop within the tank. This issue usually happens when warm water is left too long in the tank and bacteria builds up in the water. The soft water breaks down the magnesium and creates sulfate gas within the water heater
The minerals in our water tend to build up in our units over time. When enough builds up, you get cloudy, yellow, brown, nasty water. If you notice rusty or rust colored water coming from your faucets, then you may have a build up of rust or damaged piped within your unit. Flushing your tankless water heater with a pre-made descaling solution or regular distilled white vinegar should solve your problem. It’s good to be in the habit of cleaning your tankless water heater at least every six months. If you know you have hard water problems, ask us about water softeners to help keep your unit in top condition.
If your rotten egg or bad smell is caused by stagnant water within the tank, then you will probably need to have the water heater replaced. On some DIY websites they may recommend draining and flushing the tank. However, even if you can flush the bacteria out the smell will likely stay within the tank and you’ll continue to experience the same problem
Proper gas pressure coming to your tankless heater has to be provided. Check the gas valve and ensure that it is open, and that you have paid your gas bill. Check all sensors, wiring fuses, and electrical components to ensure they have not burned out. Ensure there is no condensation or debris on the burners that may cause them to not ignite. If the flow is too low, the burner will not ignite. Low pressure is one of the most frequent tankless water heater problems and is easy to fix.
Here are the ignition failure codes found on some tankless brands:
Takagi Tankless Water Heater – Error Code 111, 11 or 3
Electric Tankless Water Heater Rinnai – Error Code 11
Navien Tankless Water Heater – Error Code E003
Noritz Tankless Water Heater – Error Code 11
The ignition failure on tankless water heaters can occur to any brand and model, no matter how advanced or not it is. The failure can be caused by a problem inside the water heater or due to an external cause.
Water leaks on your water heater are typically caused by leaking valves and plumbing connections. If you notice a leak, try to trace it to the origin within the plumbing pipes. If it is not immediately noticeable, then it’s advised that you should shut off water to your water heater, and call a local plumber in your area to come inspect the situation.
Here at Paschal, we specialize in installing and maintaining Navien brand tankless water heaters. Navien NPE-2 Series and NPN Series high efficiency tankless water heaters provide endless domestic hot water, all while keeping your utility bills low.
Navien Premium Efficiency condensing tankless water heaters are the #1 selling high efficiency condensing tankless water heaters in North America. The NPE-2 series offers ultra-high efficiency up to 0.96 UEF to keep your utility bills low, endless hot water, and exclusive ComfortFlow® technology with a built-in recirculation pump and buffer tank.
Navien Premium Non-condensing tankless water heaters deliver a continuous flow of hot water for as long as you need it. No waiting for a tank to reheat more water, wasting time and energy. NPN series is the only non-condensing tankless water heater to offer NaviTech™ stainless steel heat exchanger and stainless steel burner for durable and eco-friendly performance.
|Efficiency||Ultra-high Efficiency (UEF up to .96)||High Efficiency (UEF > .80)|
|Venting||PVC acceptable||3″ x 5″ metal concentric required|
|Installation Location||Indoor or Outdoor||Choice of interior or exterior|
|Long term operating cost||Lower than typical non-condensing tankless and storage tank system||Could be higher than condensing but lower than storage tank systems|
|Durability||Stainless steel heat exchanger extend service life||Stainless steel heat exchanger extend service life|
|Dimensions||Slightly larger than non-condensing, about 70-80% smaller than tank system||Slightly smaller than condensing, 80% smaller than tank system|
|Initial cost||Usually higher than comparable non-condensing||Usually lower than comparable condensing|
|Maintenance requirement||Annual service recommended||Minimal|
When a hot water tap is opened, the tankless water heater detects the flow
The flow sensor activates to determine the amount of hot water needed
The igniter activates
The gas control valve opens to supply the correct amount of gas
The fan and venturi activate to provide the correct amount of gas and fuel
The premix burner ignites providing a flame to heat the water
Cold water is pre-heated in the secondary heat exchanger
Pre-heated water passes from the secondary to the primary heat exchanger
The unit determines outgoing set temperature and adjusts the flame to heat the water
Heated water moves to the buffer tank
Desired hot water amount delivered to the faucet
If you’ve tried these DIY fixes or you have a totally separate issue, we’re here to help. Our licensed Northwest Arkansas plumbers can assist you with all your tankless water heater needs. Our plumbers in Northwest Arkansas, Southwest Missouri, and Fort Smith work on every brand and make of tankless water heaters, including Navien, Rinnai, Rheem, Bosch, EcoSmart, Stiebel, and more. Call us!