Do Tankless Water Heaters Leak?

Spoiler Alert: Yes, they do. ( The important think to understand is when and why this can happen and how to fix any leaks that do occur.)

This is a question that baffles many thousands of people. How can a device that stores literally zero millilitres of water start to leak water? I mean, you’d understand if a tank-based, traditionalist, inefficient water heating system or unit would leak, right? It’s a huge tank, and if there’s a hole or poor welding or manufacturing quality anywhere – or it just rusts – it will leak, right? Well, that’s the case in tank-based water heating solutions. But what about tankless water heaters?

Yes, it’s perfectly true that they leak, and this happens very often. But is this a reason to completely replace your tankless water heater – which is typically very pricey indeed – as soon as you detect a leak? We don’t think so. To save you many hundreds of dollars, we’ve compiled this article.

Tankless water heating systems and units can be incredibly complicated to manage and maintain in certain circumstances. For example, having a system with a leak isn’t as simple as pushing a button. Fixing a leak is not as simple as adjusting the temperature, and even that can sometimes be tricky on industrial tankless water heating systems.

But let’s think about fixing a leak. Could it be an internal problem? Yes. Could it be a problem with the connections that either you or the plumber that had been employed by you have made? Absolutely. In fact, this is the most common reason.

Yes – poor connections and weird screwing is the main cause of leaks in tankless water heaters. But can this really be combatted by yourself? Yes! Again, absolutely. Firstly, let’s dive straight in to the first reason that tankless water heaters leak, and also jump into a very clever way of fixing the irritating problem.

Reasons your Tankless Water Heater is Leaking and How to Fix it

This section will cover possible reasons for the leaking of water from your tankless water heater, and provide basic, generic solutions on how to fix them. Although, as always, please be advised that there are certain procedures that you may be uncomfortable carrying out on your own, and in these instances, you should always contact a professional of the industry to carry out these tasks for you.

This way, you can prevent injury to yourself, and possibly even save yourself thousands in property damage from a continually leaking pipe.

Firstly – Is your temperature and pressure relief valve moist or wet?

When the pressure grows too high inside a tankless water heating system, there is only one solution that will prevent the entire system from blowing up and potentially catching fire, as well as setting your property on fire especially if the system is powered by a gas such as propane.

This one solution is to release this pressure. Thankfully, some guy many years ago invented the pressure release valve, which allows for the safe discharge of pressure from the tank. This is usually directed straight downwards – and thank God for that – to prevent high pressure hot water or gas splashing in your face, or the poor face of your plumber.

But how do we fix this?

Well, if this really is the problem, stand well back from your water heating unit. If there really is a problem with the internal functioning of the tankless water heater as a result of the pressure being too high, and your pressure release valve doesn’t appear faulty in any way, you face the risk of the entire system exploding.

As this is a pressure issue, always ensure to get a professional involved in this stage. Do not risk your own life or the lives of those around you, such as family members, and call a professional straight away. This procedure shouldn’t cost you more than $100, and you will likely pay much less if it’s only a faulty valve. Don’t take the risk.

Secondly – Does the leak appear to be coming from the main body of the system?

If the first scenario isn’t the case, and your pressure release valve is perfectly dry, is the water dripping out of the main body of the tank?

This could be an issue of sediment or rust within the system, causing a leak. In these situations, it is highly likely that you will have to replace the entire system, as you cannot simply “patch up” a break in the pipe if all goes wobbly, for the simple reason that there is not a single material in the world that is cheaper than an entirely new system that can be used to fix a leak inside a tankless water heating system without melting as soon as the propane or heating element is turned on.

Unfortunately, as hinted at before, an entire system replacement may be necessary for protecting the safety of you and those around you. It is often the case that a leak from the main body of the system can do horrific damage, and even damage the electrics of the unit itself.

Not only this, but you may find yourself in a battle with water spraying everywhere – this usually happens in this situation, and you should get a plumber on the job as soon as you possibly can, as this can cause tremendous damage to the property surrounding your tankless water heating unit.

We can not stress this enough – always call a plumber if the leak appears to be at a high pressure, and if you feel safe doing so, always operate the pressure release valve or cut off the water supply to the unit altogether. It might just save your life.

Thirdly – Are the water intake and output lines well connected to the main body of the unit?

This is most likely your problem, but we’ve left it to last as knowing whether your water heating system is about to explode on you is far more significant, and you should know this before you step forward and start fiddling with the system, and potentially cause yourself lifelong burns and physical damage.

Closely examine the water input and output lines, and ensure that they are strongly fitted, and that no water is leaking from that area of the water heating system or unit. It is essential that you examine this thoroughly, as this could be just about the most common cause of water leakages, especially if you have installed the unit by yourself.

But what is the solution? Is it simple? Is it expensive? Many people come to worry about these questions, and rest assured that the solution is much simpler than you might think. In fact, it’s probably a method used to fix all sorts of things.

Remember the “turn it off, then turn it back on again” fix that works for just about everything? Yeah, well – this is that but only with a few more twists and turns and screws and threads.

It’s simple, and not expensive. Simply turn off the cold-water intake using a shutoff valve, and unscrew both water intakes and output lines, and screw them back on. Ensure you dry everything around the affected area, and then turn the water back on.

If the leak is still there, we would strongly encourage you to replace the lines or cables leading the water in, as their threads may be faulty.

However, not to worry. These threads and cables will only set you back a maximum of $20 if you look on a website like amazon, and you’ll likely get them delivered the next day. They’re very simple to install and replace, but you should always take the following precautions:

  1. Always ensure that the water supply is switched off before unscrewing or unthreading any cables, lines or pipes.
  2. Always ensure the tankless water heating unit is set to it’s “off” setting, and there is no current flowing through it or propane being pumped into it.

Once you have ascertained that you are safe to proceed and have taken the correct precautions, you can proceed to install the pipes.

And there you go!

Final Words

The solutions can really be quite simple to these leaks. Yes, they can occur, but this isn’t very often, and usually happens in the case of poor installation and setup. As we have recommended multiple times in this article – if you are not comfortable performing a task on your own, or feel in danger of the tankless water system exploding, always ensure you call a professional as soon as possible.

Not only are you at risk of causing serious damage to yourself and your property, but you may not be able to experience a warm shower for a long time if this happens – especially if it damages your gas lines.

However, if you’re able to fix the problem quite easily, or can afford to replace your unit altogether (although always consult a plumber first) never hesitate to do so. After all, it’s your home, and if you want hot water and afford it, go for it!

About the author

Steve Bates

Hi, I'm Steve and I currently reside in Chicago, Illinois. Although for most of the last 20 years I was a partner in a HVAC company down in Austin, Texas.

I understand the frustration involved with dealing with water heater repairs and replacing or upgrading to a new, more efficient model.

My aim is offer some basic advice on fixing home hot water systems. And if a repair isn't possible, then to make the process of selecting a new water heater – be it gas or electric - as simple as possible.

So that you can save money and have a safe and reliable hot water system in your home for many years to come.