Furnace Humidifier Water Always Running – What To Do?

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For some reason, you always hear the trickle of your humidifier water. Because of this, you are wondering how to fix the problem and stop the water and electricity waste. In this post, we gather up-to-date research to answer your question thoroughly.

When your furnace's humidifier water is always running, there are a few different steps you can take to troubleshoot and fix the problem. These steps are as follows:

  • Check The Solenoid Wiring
  • Replace/Clean your Solenoid Valve
  • Check the Reservoir Integrity
  • Check the Humidistat Setting
  • Call an HVAC Professional

Keep reading the rest of this post for details on each of the above bullet points. This guide will set you well on your way to diagnosing and fixing a constantly running humidifier water supply. To conclude, we answer several questions related to the topic of this post.

A disassembled furnace humidifier, Furnace Humidifier Water Always Running - What To Do?

Diagnosing Constantly Running Furnace Humidifier Water

Most humidifiers function by wetting an air-permeable cloth-like membrane. The furnace fan then blows air through this membrane, evaporating some water and adding humidity to your air.

Some systems have a valve that drips the water directly onto the membrane. Other systems have a holding tank and a mechanism that dips the cloth-like membrane into and out of that tank. Troubleshooting these two different system types are slightly different.

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Both systems use a solenoid valve that must be wired correctly and may fail or clog. However, only the second system type has a reservoir that may fail.

Now, we will cover the troubleshooting steps for diagnosing why your furnace humidifier water is always running. We consider furnace humidifier water that always runs even when the furnace fan is off and furnace humidifier water that runs too heavy but only when the furnace fan is on.

Worker checking the furnace duct for any signs of damage

Check The Solenoid Wiring

If your furnace's humidifier water runs even when your fan is off, it is likely an issue relating to the solenoid valve. The first step to understanding the problem is to check the solenoid's wiring. First, flip the furnace breaker to make this process a much safer one.

For clarity, it is important to understand how the solenoid works. This device is a valve that is usually off unless powered. The solenoid valve will open and let the water run through when powered.

Thus, a furnace humidifier's solenoid valve's power should break off from the wire that powers your fan. This wiring then goes to a 24-volt converter and the solenoid valve. The solenoid valve only opens when the furnace powers the fan in this sequence.

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Instead, it is a common mistake that the solenoid's power instead is routed from the line that feeds the entire furnace. This configuration leads to a solenoid valve that is always powered, so it is always open. This leads to that constant drip.

It is highly recommended that you only perform electrical work that you are comfortable doing or, better yet, certified to do. If you can move the wiring for the solenoid valve, then reconfigure as recommended above, and it should fix your dripping problem.

Replace/Clean your Solenoid Valve

If you find that your solenoid valve is wired correctly and you still have a constant drip, the next thing to check is the valve itself. It is common for these valves to get stuck open from debris or mineral buildup.

To fix this issue, you will want to flush the valve and line with some directed water pressure. You can also try to clean out the solenoid valve gently. Usually, there should be some sort of hose, line clamp, or fastener that you can undo to access the valve.

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As you do this work, be careful not to get too much water into the furnace's relatively sensitive inner workings.

If cleaning or flushing does not work, take the step of replacing the valve. As before, be sure to flip the breaker before performing any electrical work, or better yet, hire an electrician or HVAC technician to make the switch for you.

Check the Reservoir Integrity

If you have a furnace humidifier that relies on a reservoir to wet the membrane, you may be dealing with a reservoir integrity issue. This is a relatively easy problem to identify. However, it is still wise to flip the furnace breaker off before doing this work.

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All you need to do is inspect your reservoir for cracks or failures. Usually, you will be able to see where the water is dripping or feel the water on the bottom of the reservoir.

You could try to fix this problem with any high-powered glue or tape. However, the best way to solve this problem is to replace the reservoir or the entire humidifier.

Check the Humidistat Setting

If you find that your humidifier only runs when the fan is on but still makes your house way too moist, you may be dealing with a humidistat issue.

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The humidistat is the device that measures your home's humidity. Usually, the humidifier will only turn on if your home's humidity is lower than the threshold set on the humidistat.

Thus, you may have a humidistat that is set way higher than the actual humidity you desire. If this is the case, try to set the humidistat to a lower humidity threshold and see if that fixes the problem.

If changing the humidistat setting is not fixing the problem. The humidistat is broken or faulty. To fix this, first, check that all wires are securely fastened. Then, if the issue persists, you should consider replacing your humidistat.

Call an HVAC Professional

Finally, if any of these steps or fixes seem too dangerous or complicated for you, consider calling an HVAC professional to fix your constantly running furnace humidifier water.

An Hvac service technician testing the furnace

Hiring a professional ensures that the job will be done right and protects you from the risk of harmful electric shock.

How much water should drain from the furnace humidifier?

According to Filters-Now, an online retailer which sells furnace humidifiers, it should take 2.5-minutes to 5-minutes to fill up a quart jar from the furnace humidifier drain. Remember, this only applies to a running furnace and a home with low humidity. Ideally, an off furnace should be draining no water.

How do I turn off the water to my furnace humidifier?

The water that feeds your furnace humidifier is run from the main house water. Where you turn the humidifier water off depends on how the unit was plumbed.

It is customary to install a shut-off valve at the location where the humidifier water splits off from the main house water. Find this location by following the humidifier's water line until it joins another house line.

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If there is no shut-off valve at this junction, it is likely that the only way to shut off the humidifier water is by shutting off the water to the entire house. These whole-house shut-off valves are usually located near your water meter or at the water inflow to your home.

While the water is off, it might be a good idea to install a more easily accessible shut-off valve near your humidifier. This makes future repair work much easier and allows you to turn the humidifier off during seasons or times when you are not using it.

When should the humidifier be turned on?

HVAC technician checking the air duct

This depends on when your home is experiencing very dry air. In much of the United States, dry air is more prevalent during the cold winter months. However, the summer is also a very dry time of year for the desert southwest.

The moral here is simple, if you are experienced humidity that is lower than you prefer or find healthy, keep your humidifier on. On the other hand, if the natural humidity is high enough, or if you are leaving on an extended vacation, it is the best call to turn the humidifier off.

As a caveat, if you are experiencing significant indoor condensation, your humidifier is probably doing more harm than good. This excess moisture can lead to mold, mildew, and rot. If this is the case, turn your humidifier down or off.

What should my furnace humidifier be set at in the summer? In winter?

Generally, you should keep your home's humidity somewhere between 30-percent and 50-percent. This level is considered comfortable to live in by most.

House humidifier infographic

However, in the winter, you may find that very high humidity leads to excessive condensation on your exterior windows. If this is the case, consider lowering your humidity levels to closer to 20-percent or 25-percent.

Additional Reading

To learn more about humidifiers, read these great HVAC Seer articles:

In Closing

In this post, we answered the question of what to do if your furnace humidifier's water is running continuously. The answer includes several possible issues that lead to this problem and their respective fixes. To conclude, we answered a few related questions. Good luck!

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