A damaged flow sensor can cause your tankless water heater to run hot and cold. The flow sensor measures the water entering your system and sends 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.
Fluctuating hot and cold water could be a couple of things. Firstly, it could just need flushed with a descaling liquid such as vinegar. Secondly, it could be a dirty flame rod not sensing the flame well enough. Both of those things are usually addressed when you do a tankless service. Have you had it serviced?
It's possible your water heater tank is allowing retrograde (backwards) flow from the tank through its cold water supply pipe into other cold water pipes, causing variable amounts of warm water in place of cold at some of the taps, particularly th...
The issue may be the flame rod, clogged exhaust/intake screen, clogged condensate drain, plugged up heat exchanger, bad mixing valve after the unit, etc. You'll need to get a tankless specialist out to find out what's going on with it.
Blocked heat exchanger
Sludge and sediment buildup is fairly common in older boilers, especially when the filters are old. This blockage will then cause water to run hot and cold intermittently.
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.
Symptoms of a faulty diverter valve often include inconsistent hot water flow and radiators not heating properly. Homeowners may notice that radiators remain cold even when the boiler is on. Inconsistent water temperatures are common, with water switching from hot to lukewarm or cold unexpectedly.
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.
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.
Water heater leaks are frequently behind water heaters that run constantly. When a water heater leaks, the leak essentially drains the hot water tank, and the system loses hot water. If you find signs of a leak, call your plumber right away to schedule water heater repairs.
Anti-Freeze Measures for Tankless Water Heaters
Insulating exposed pipes, keeping the area around the heater warm, and regularly using your hot water are effective anti-freeze measures. These steps help maintain a consistent temperature around the unit, reducing the risk of freezing.
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).
The most complicated and time-consuming tankless water heater maintenance is typically descaling and flushing out the unit. Even with the inline water filter, lime and calcium deposits can build up inside the tankless system. If you have hard water, it's a good idea to descale and flush the unit once a year.
A tankless water heater requires a certain amount of water pressure to function properly. If the incoming water pressure is too low, the unit will not be able to generate enough hot water. This is often caused by a plumbing system crossover, where the cold and hot water lines are connected.
Just like a tank unit, tankless water heaters need to be flushed once per year. Homeowners with hard water should consider flushing and cleaning the unit even more frequently, perhaps every six to nine months because of the excess amounts of magnesium and calcium found in hard water supplies.
One of the most common questions asked by consumers about tankless water heaters is how long they will last. A tankless water heater can last anywhere from 15 to 20 years with proper maintenance and operation. In comparison, a standard tank water heater normally has a working life of 10 years or less.
These water temperature fluctuations can be caused by:
A plumbing system crossover where there shouldn't be one. Improperly lengthened venting pipes. Damaged flow sensor — something that should be checked during your annual plumbing maintenance appointment. A dirty water filter on the cold water inlet.
Are you scratching your head and asking, “Why does my hot water heater run cold so quickly?” If your hot water keeps going cold, the culprit could be sediment buildup, a broken heating element, a faulty dip tube, or simply high water usage in the household.
No hot water coming from taps, or water is lukewarm. 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.
Signs a diverter valve is stuck
If your diverter valve is sticking, you'll soon know about it. Whether that's standing under a cold shower because you've got no hot water or facing a chilly evening because your radiators won't switch on. Other things to look out for include: No hot water from the taps.
$100 – $350 shower cartridge replacement cost
Plumbers charge $100 to $300 in labor alone to replace a shower mixing valve or diverter valve.