Overloaded Demand: Tankless water heaters provide hot water on demand, but they have limitations on the amount of hot water they can produce simultaneously. If multiple fixtures or appliances are drawing hot water simultaneously, the heater may struggle to keep up with demand, resulting in cold water.
Typically when a tankless water heater goes cold mid shower it's because either you flow of water is too much for the heater to keep up with, or ironically the flow of water is too low and the heater doesn't think water is passing through and it shuts off.
Low water pressure
If your shower goes cold after a few minutes, it might be that you've been unlucky enough to be showering just as the water pressure dropped. The best thing to do is see if other taps are experiencing lower pressure, plus check if your neighbours are experiencing a problem too.
Tankless water heaters rely on ignition to heat water on demand. If the ignition fails, you'll be left with cold water. This could be due to a variety of reasons such as a faulty igniter, gas supply issues, or a dirty burner. In such cases, it's best to consult a professional technician to diagnose and fix the problem.
If your water heater isn't working properly, several fairly common issues can lead to less hot water availability. A malfunctioning thermostat, broken dip tube, and sediment buildup are the most common repair issues that can explain why your shower quickly runs out of hot water.
A broken or burned-out heating element (immersion) could be the culprit for cold water in the hot water tap. As we use our water heater, the heating element gets worn out over time, which reduces its efficiency and lowers the maximum water temperature, until it completely stops heating the water.
First, find the shut off valve for the hot water and see if it's closed. If so, opening the valve could remedy the situation. But if the water still remains warm for only short periods of time, you may have a blockage or obstruction in the pipes or a problem with your bathroom shower valve.
If your tankless water heater keeps shutting off during your showers, it may be struggling to meet the high demand. Consider reducing water flow or using low-flow showerheads to alleviate the problem.
What temperature should a tankless water heater be set to? For most residential uses, a temperature setting of 120° - 125°F is sufficiently hot and will protect against scalding. You can set your residential tankless water heater higher, but know that a child can be burned by 140°F water in just a couple of seconds.
Install a Recirculating Pump
With a recirculating pump, the water that travels through your tankless heater no longer sits in the pipes to cool off once you shut off the outlet.
Another possible answer is that your pressure-balancing valve may be at fault. A thermostatic mixing valve (TMV) is a valve that blends hot water with cold water to ensure constant, safe shower and bath outlet temperatures, preventing scalding. Pressure valves open and close pipes in accordance with water flow.
Sediment build up inside of your water heater tank. A broken dip tube. A water heater that is nearing the end of its lifespan. A faulty water heater thermostat.
Depending on the model, a tankless water heater can supply hot water for your entire home or just a single point, such as a shower, sink or appliance.
Just like a dirty water filter, mineral buildup from hard water can create issues with how tankless water heaters create hot water. In fact, this type of buildup is the number one cause of temperature problems.
The recommended temperature setting from the Consumer Product Safety Commission for a tank and tankless water heaters is 120 degrees.
Overloaded Demand: Tankless water heaters provide hot water on demand, but they have limitations on the amount of hot water they can produce simultaneously. If multiple fixtures or appliances are drawing hot water simultaneously, the heater may struggle to keep up with demand, resulting in cold water.
Check to ensure the water supply valve is open, and there is no blockage in the pipes. If the water supply is blocked, you may need to call a plumber to fix the issue. If the heating element or burner is faulty, it can cause a no-hot water issue. Check to ensure the part or burner is clean and debris-free.
One common cause of a drop in water pressure and a loss of heating in a tankless water heater is a clogged water filter. The water filter is responsible for keeping sediments and dirt out of the unit, but over time, it can become clogged and restrict the water flow.
Common causes of inadequate water: Water heater problems, issues with thermostatic mixing valves, and pipe insulation troubles. Impact of shower head design: How flow restrictions or low-flow shower heads can affect water temperature.
Having intermittent hot and cold water is quite a common problem with instantaneous systems. This can be caused by a range of things including: The diaphragm on the gas meter could be faulty. Not enough gas may be getting to your hot water system (which can be caused by an under-sized gas bottle).
If your shower is running out of hot water, it's likely due to one of the following problems: Malfunctioning thermostat. Broken dip tube. Sediment buildup in the tank.
Shower mixing valves usually have a default temperature, which users can adjust to their preference by twisting the hot and cold water knobs. Yours is probably inside the wall behind the shower handles if you need to access it.
Inspect the thermostat, which controls hot water heater temperature. If someone has recently changed the setting, that could be the reason behind your lukewarm water woes. However, if the temperature setting is correct, the thermostat itself might be broken. You can have the thermostat replaced fairly inexpensively.