Furnace Leaking Water from Overflow Pipe

The moment you find water around your furnace seems like the end of the world for you.

Lucky you, this is not as tragic as you might think it is. Yes, this will ruin the flow of your plumbing system, at least not immediately.

There are many reasons why water drips in your furnace from that overflow pipe. And one of the most popular reasons is a damaged condensation drain.

Let me tell you more about it.

A leaking overflow pipe isn’t really a problem. Most of the water that comes from furnace issues is easily resolved. And like issues with your air – conditioner, indoor air, and internal drain, you would need the help of a certified plumber to save yourself from exaggerated costs and severe property damage.

For instance, a pool of water that you find around your furnace can result in mold, flooding in your furnace room, or, worst of all, flooding inside your furnace. The leak water can actually damage your plumbing systems in the long run.

Here, I will teach you about the most common reasons why you see condensation from a furnace and how you can stop them from escalating.

Reasons Behind Furnace Leaking Water From Overflow Pipe

Issues with a toilet overflow pipe, float valve, expansion tank, floor drain, PVC pipe, toilet cistern, water pipe, and any part of your plumbing system are too challenging to understand and handle.

Imagine dealing with an overflowing sink, water dripping, expansion vessel failing, and furnace leaking water on your own in the middle of the night – sounds terrible, right?

But we are here to expand your knowledge of the common causes of these plumbing emergencies. Let’s start with the root causes of furnace leaks or condensation leaks.

The Types of Furnaces

There are two types of furnaces: high-efficiency gas and standard-efficiency gas.

The first thing that you have to do is to educate yourself about these two types of furnaces.

More than 80% of the time, water from furnaces happens with high-efficiency gas furnaces.

Before we look at the most common reasons for condensation in your furnace, let’s look at how you can identify the type of furnace you have.

High-Efficiency versus Standard-Efficiency Furnaces

Water that leaks in your furnaces during winter only happens in high-efficiency furnaces. It is because standard-efficiency furnaces do not leak water at all.

If you have a standard-efficiency furnace, it does not condense at all; High-quality furnaces do.

So, how do you tell one furnace from the other?

Check the AFUE Ratings

Furnaces that come with a 90 AFUE (Annual Fuel Utilization Efficiency) rating are high-efficiency furnaces. It means that your furnace comes with a 90% energy efficiency.

If it is below 90 AFUE, what you have is a standard-efficiency furnace.

The high-efficiency furnaces will have yellow stickers on the unit with their corresponding AFUE ratings.

The Condensation Pipe

High-efficiency furnaces come with a white plastic pipe (PVC exhaust pipe) that drains it. On the other hand, standard-efficiency furnaces drain through a metal exhaust pipe. You can find these at the back of the furnace.

Now, what does this have to do with leaking water from the overflow pipe?

I will discuss more on this later.

A high-efficiency furnace comes with 90% or more of the energy produced. Obviously, this is something that you would prefer.

However, high-efficiency furnaces also potentially expose your furnace to water, as some do not have a condense pipe connected to a waste pipe.

When a high-efficiency furnace uses a secondary heat exchanger to produce more heat, it causes the produced gasses to cool down. When it does, it condenses.

And this is where the PVC exhaust pipe or flue pipe comes in handy. When the furnace operates normally, you will find the condensation from the furnace vented out through this drain.

If you see leaking water from your furnace, you might have a malfunctioning drainage system.

And this brings us to the most common culprits for furnace dripping water. Here they are:

  • The condensation pipe is clogged;
  • A leak in the condensation pipe;
  • A faulty heating unit;
  • A clogged condensate trap;
  • A twisted float valve;
  • Issues with the condensation pump;
  • A problem with the secondary heat exchanger;
  • An issue with the central heating feed or cold water tank.

Gas Furnace Leaking Water from Overflow Pipes

On the other hand, a furnace leaking water from overflow pipes is common in standard-efficiency furnaces.

One of the most common reasons for this is because of the incorrectly sized exhaust pipe.

As mentioned earlier, standard-efficiency furnaces do not leak. Standard-efficiency furnaces also do not condense.

Condensation is simply impossible in these types of furnaces.

However, in case of condensation happens, most of these standard-efficiency furnaces come with exhaust pipes to solve the problem.

If you find your standard-efficiency furnace condensing, there could be many possible reasons.

One of the most common reasons is the furnace that leaks water from the overflow pipe.

Usually, the culprit is an exhaust pipe that has an incorrect size. The pipe that you have in your furnace may be too small for it to allow for enough drainage.

Obviously, the reason can be anything else. As mentioned, incorrect sizes can just be one of the many reasons.

It can also be because of a faulty heat exchanger. On rare occasions, it can be a gas leakage.

How do you resolve this?

Call a professional to fix your issue. It can be a leak, an issue with the central heating feed, a faulty central heating tank, or a problem with the central heating system. Whatever it is, it is for our professional plumber to fix it.

The first thing that might come to mind is to install bigger exhaust pipes. But this step will just treat the symptom. It will never address the problem nor keep your whole house humidifier system safe.

It will always be difficult to pinpoint why you are seeing condensation in your standard-efficiency furnace when, in the first place, this should not be possible at all.

A professional plumber will know his or her way around these furnaces, can help you detect the problem, and eventually repair it.

And in some instances, you might even have to replace your furnace.

If you are lost about who to call for help, pick up that phone and dial our number now. We can help you with your furnace problems.


Things to know about Overflow Pipes

When we talk of overflow pipes, we talk about the addition to the storage tank. It stops the water from overflowing.

It is crucial, especially in your house’s water storage systems, as it ensures that the house does not get flooded with water.

With leaking overflow pipes, you first have to identify the reason for the problem. You need to identify where the water stays. And you have to know what steps to take to resolve your problem.

Remember, a leaking pipe may not be much at first. But it will always be trouble in the end.

With an overflow pipe leaking outside, it is alarming. It may be a small leak, but it will result in a lot of hassle for you and your home.

Prolonged overflow pipe leaking will lead to water overflows and molds. It could also mean switching the entire system off if not addressed immediately.

And so, you have to deal with the issue as soon as possible.

Water Pressure Check

Check the water pressure.

Naturally, the tube will leak if it is higher than what the pipe can handle. There is a valve within the overflow pipe. It shows you if there is too much pressure and tells you about the flow of water.

Check this and ensure the pressure is within what the pipe can handle.

Determine which pipe overflows. 

Another step is to determine which pipe leaks.

Overflows do not mean the water supply is abundant.

An outflow that is at ground level means that it is your toilet pipe that is overflowing. If you see water that drips from the roof, your heating system might be the culprit.

Knowing which pipe is leaking assures you that you are dealing with the right one.

Switching the Pressure Relief Valve Off

Do you know how to switch the valve off? Do you know about the isolation valve? How about a pressure valve?

If you are unsure which valve releases water and which one to turn off, it’s best to call our plumber to give you a hand. Once our plumber identifies where the problem is coming from, you will know which part to switch off.

But of course, we’ll lecture you on this so you know what to do moving forward. Through this, you can prevent the water from flowing into the tank. It rids you of excess water loss.

Cold Water Feed, Cold Water Tanks, and Expansion Tank Leaks

If you see a pipe that extends through a massive water cistern, it is the cold water feed.

It provides water to your sinks. If there is a sink overflow pipe or any pipe that leaks, it can be because the water inlet in the tank is not turning off or the copper cylinder is faulty.

Or it can also be the water that goes back to the outlet pipes or toilet cisterns.

Should this be the case, check the float valve or washer. Make sure that they are fine. If not, you might need a new float valve.

Do You Need Professional Help With a Gas Furnace Leaking Water?

In many cases, a furnace leak will be resolved by a professional plumber. However, there are burning gas cases where you would need the expertise of a gas-safe engineer. A leaking furnace, faulty heating system, and broken hot water feed are something you do not ignore.

Call us and have our expert take a look at the leaking furnace and check your entire HVAC system. It can be a concern with your boiler overflow pipe dripping, a problem with your hot water cylinder, a dripping overflow pipe, an issue with your condensate pump, a faulty secondary heat exchanger, issues with the air conditioner, or whatever it is that bothers you.

You will need help and assistance in disassembling and reassembling the furnace or working on that copper cylinder. Dealing with a condensation leak or furnace leak is a complex process, and most of the time, it is the very reason why you need Emergency Plumbing Squad in the first place.

Call us, and let us do the job for you.



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