If you have a聽tankless water heater, then you know that it聽will聽run hot and cold on occasion. This is because tankless聽water heaters聽are聽designed聽to run without any delays as they heat water. It’s not聽uncommon聽for tankless heaters to be running on high one second and low the next.
The problem is that this聽may聽potentially make your tankless water heater less efficient, which may cause your energy bill to go up! Let’s聽discuss聽why your tankless water heater runs hot and cold, what causes these fluctuations, and how they can be聽resolved.
Cold Water Sandwich
Although the situation is rare, you聽fixed聽come across a tankless water heater problem known as a cold water sandwich. Your water heater will聽provide聽hot water for a few seconds, followed by a blast of cold water (cooler), then ample warm water. It almost聽feels聽like your tankless water heater shuts聽down聽for a聽moment聽before heating water, but that’s not the case.
This can聽occur聽when one fixture is聽turned on聽immediately after another fixture has been turned off. You’ll get some hot water stored by the faucet, followed by cold water from the tankless water heater before the gas burner can fully heat the heat exchanger.
If you’re washing your hands, a cold water sandwich probably isn’t a聽big聽deal. But it’s聽annoying聽if you’re聽getting聽a cold shower when you want hot water. Here’s how you can聽fix聽this annoying water temperature fluctuation.
How to Fix It
You have two options for fixing a cold water sandwich: installing a recirculating system or聽adding聽a small tank water heater. In fact, some manufacturers today already聽include聽this buffer tank.
If you don’t need a lot of hot water at聽once, adding a recirculating system or return loop to your tankless unit will聽take care of聽the heat exchanger delay. However, it’s important to note聽more聽energy is consumed in the process.
Have more significant hot water needs? You can聽bolster聽your tankless water heater’s capacity and聽eliminate聽that burst of cold water by adding a small tank water heater. This water heater connects聽via聽the return loop. It only has a five-gallon storage tank, making it very energy efficient.
But don’t forget that when聽appropriately聽sized, a tankless water heater’s capacity is聽essentially聽endless.
Wrong Gas Line Size
Most tankless water heaters require you to (size) extend your gas line for ample gas supply. If you’ve already聽completed聽this, but it’s still running hot and cold, then your line is the wrong size. Upgrading your gas meter聽may聽be聽required聽to ensure your water heater is聽receiving聽enough fuel.
How to Fix It
The聽ideal聽line size for a tankless water heater should be between 1/2″-3/4″ in diameter. If yours is too small, call a聽天美传媒聽Expert for聽gas line replacement.
Improper Plumbing System Crossover
Tankless water heaters require you to have a direct connection聽into聽the supply and return lines. If plumbing was done incorrectly or a pressure balancing shower valve needs repair, cold water can聽reach聽the hot water line, making the hot water lukewarm. You’ll get bursts of hot and cold water until that line heats up after聽continuous聽use.聽Diagnosing聽this problem can be difficult聽on your own, without help from a professional plumber.
How to Fix It
You have two options when it comes to fixing an improper plumbing system crossover. You can either raise the thermostat on your tankless water heater or install a pressure balancing valve.
If you聽decide聽to raise the thermostat, then you’ll need to constantly use hot water at every tap. This will聽steadily聽raise the temperature of your hot water supply, allowing it to heat up in your return line.
If you聽decide聽to install a pressure-balancing valve in your gas line, it monitors the temperature of your home’s incoming gas line. It will also balance out聽any聽excess pressure when cold water enters the system, so you won’t get bursts of hot and cold water.
Broken Flow Sensor
A聽damaged聽flow sensor can cause your tankless water heater to run hot and cold. The flow sensor measures the water entering your system and聽sends聽that information to your unit’s control board. If there’s a burst of cold coming into the system, then the controller adjusts the flame. This ensures you get enough hot water throughout your home聽promptly.
How to Fix It
You need to聽diagnose聽the source of the聽damage.聽Take a look at聽your system’s gas pressure, thermostat or water heater assembly for issues. If you have a聽malfunctioning聽flow sensor, it’s important to have聽天美传媒聽replace it so your tankless water heater聽operates聽efficiently.
Dirty Water Filter
The water filter used on the cold water inlet of instantaneous (tankless) water heaters聽lengthens聽its life span and maintains energy efficiency by聽filtering聽(sediments), calcium, lime and iron. If it gets too dirty, you’ll not only be getting聽surprise聽bursts of cold and warm water, your natural gas bill can聽rise sharply. You might聽have聽to descale your tankless heater if there’s聽excessive聽mineral buildup.
How to Fix It
Regularly聽replace聽your system’s filter so it can聽function聽at its best. We聽suggest聽doing this聽around聽every six months or so.
Corroded Lines
Corroded lines (in your home) are a common reason why you’ll experience bursts of hot and cold water. A聽few聽signs of this problem include discolored water or rusty-brown particles in the water. As water聽moves聽through your home’s plumbing system, internal corrosion can聽shake loose聽and become trapped in your tankless heater’s filter.
How to Fix It
You聽need to聽call a聽天美传媒聽plumber for an inspection. Corroded lines can聽result in聽more serious problems beyond tankless systems and聽should be聽replaced.
Mineral Buildup
Just like聽a dirty water filter, mineral buildup from hard water can聽create聽issues with how tankless water heaters聽create聽hot water. In fact, this聽type聽of buildup is the number one cause of temperature problems.
How to Fix It
It’s best to call聽天美传媒聽for a plumbing inspection. Depending on the severity of the issue, we聽may聽need to descale your tankless system聽or install a water softener.
Hard water is a common problem for North American homeowners. Nearly 90% of households in the U.S and 85% of households in Canada have hard water.
Not having soft water can聽cause聽a lot of issues,聽such as:
- Scaly pipes and water heater
- Soap scum and detergent buildup
- Dry skin
- Streaky dishes and聽faded聽clothing
- Lime deposits in other hot water appliances like your dishwasher and clothes washer
Let the Experts Handle Your Tankless Water Heater Needs
One of the most聽dull聽things about a tankless system that runs hot and cold is how聽hard聽it can be to聽determine聽why your water heater is doing this. Your Expert聽plumber in the U.S聽will offer professional advice as we聽walk you through聽what needs to happen next.
This includes diagnosing tankless water heater problems to聽fixing聽any issues we might聽find聽during our visit. Don’t let frustration get the best of you! Contact us at (866) 963-7996 today to schedule your appointment.
