Common Tankless Water Heaters Issues & How to Fix Them

You turn on a faucet and have a good flow of water, but it’s not getting hot. There are quite a few possibilities.

1. Too Many Appliances Running At Once – Think about what other appliances or fixtures are running at the same time. If you’ve got a load of clothes in the laundry, the dishwasher is running, and a person is showering, chances are you’re pushing the limits of your water heater’s capacity. Try choosing your most important activity, turning off the other appliances, and trying to run hot water again.
2. Your Faucet is on Too Low – Did you know your water heater actually requires a minimum amount of water to flow through it before it starts heating? If you have a faucet practically dripping, it might be under your water heater’s radar. Try turning your faucet on higher and see if the water gets hot.
3. Your Breaker is Tripped – Whether you have a gas or electric tankless water heater, it needs electricity to operate. There’s a chance your breaker is tripped, so the water heater unit has no power. Try looking at your water heater to see if you see any lights on. If not, go to your breaker panel and reset the breaker. If it continually trips, you probably have a bigger electrical problem and need to call in a licensed electrician to check on things.
4. Your Gas Isn’t On – A gas tankless water heater will require a gas supply as well as electricity. Double check that you’ve paid your bill, your propane tank isn’t empty, and that your gas valve is fully in the on position.
5. Something is Clogged Up or Dirty – Debris or buildup can actually block several parts of your tankless water heater and cause problems. Luckily, most tankless water heaters will self-diagnose and notify you of a problem. Check your vents and air intakes for blockages and be sure your burners are clean.
6. You See an Error Code – If you see an error code on your tankless water heater, you need to look up the error code to see what the issue is so that you can fix it. You can look up the error code in your user manual or Google your brand name’s tankless water heater error codes to find a list. Some error codes have a simple fix, but some may require getting a licensed plumber involved.

It can be quite jarring to put your hand under your kitchen faucet and discover the water is scalding hot. The scalding temperatures can be dangerous, so you should call a professional plumber, like Reliant Plumbing, when the water makes fixtures or pipes too hot to touch. Here are a few potential root causes:

1. Your Thermostat is Set Too High – Fortunately, this is a quick fix. Check your tankless water heater’s thermostat to see where it’s set. We recommend setting the temp at 120 degrees F. If it’s higher than this, try turning it down, waiting a few minutes, and then test the water temperature at a faucet again.
2. Faulty Temperature Sensor – Tankless water heaters have a temperature sensor that protect the unit from overheating. Over time, this sensor can fail because it’s dirty or it has simply gotten too old. You should first try cleaning the sensor. If this doesn’t correct your problem, it may need to be replaced.
3. Something is Clogged Up or Dirty – Debris or buildup can actually block several parts of your tankless water heater and cause problems. Luckily, most tankless water heaters will self-diagnose and notify you of a problem. Check your vents and air intakes for blockages and be sure your burners are clean.

In the plumbing field, we call this the dreaded cold water sandwich. This can happen surprisingly often with tankless water heaters. It usually occurs during back-to-back showers. The hot water you get in the beginning is actually the leftover hot water from the previous person’s shower. Then, the water runs cold while the tankless water heater is heating up for your shower. Once the heater does its job, you have hot water like normal.

There’s really not a great fix for this issue. Make sure to run your water for a few more minutes before you hop in the shower. If it something you can’t stand, you may want to consider a hybrid water heater instead.

You’d be amazed how many different ways our customers can describe water that is off. Whether you think it looks yellow or smells like rotten eggs, something is not right. Your water should always be clean, clear, and scent free. If your water is anything else, you need to flush your water heater.

We can’t stress enough the importance of flushing your tankless water heater at least once per year. If you go longer than a year without flushing, your unit can grow mold, fungus, and bacteria or build up rust and sediment. The good news is this is actually an easy fix! You just need to flush your tankless water heater.