Annual Sediment Flush For Your Outdoor Wood Furnace

Annual Sediment Flush For Your Outdoor Wood Furnace

How to Protect Your Outdoor Wood Boiler from Sediment Damage - The "Secret Killer" 

What is this “Secret Killer”, and how can I stop it?

First, the best news is that the process of protecting your outdoor wood furnace from this secret killer is absolutely FREE. And it takes only about 5 minutes per year.

The Secret Killer is SEDIMENT. It builds up in your furnace water. It can be corrosive and cause damage. Even if you properly use the water treatment, sediment can build up in your furnace water and cause problems.

Sediment Buildup


 "Annual Sediment Flush"

The fix is simple: Just open the drain in the bottom rear of your outdoor wood stove for a few seconds until the water runs clear. It may appear like muddy water at first, but in most cases, it will run clear after only a few seconds.  If your water does not run clear, you will need to completely flush your system, but this is rare.

GX Model furnace owners need to flush BOTH rear drains.

We recommend that you take this simple step each year when you collect your water sample to send to the for your FREE water analysis testing Be sure to flush out the sediment before you collect the water sample. 

Remember that all outdoor wood burning boiler systems must have a high temperature water filter. This is your first line of defense against the damaging effects of sediment. If you did not obtain a filter when your furnace system was installed, please contact us, or visit for more information.

Visit our online store to browse for more outdoor wood boiler parts!

Operating Furnace FAQs:

  • Am I burning too much wood?

You may be. Is the wood properly seasoned? Have you cleared the firebox? High wood consumption can be caused by a number of factors.

  • Can I leave my Outdoor Wood Burner over the weekend?

You may have someone "feed" your furnace for you or you may lower the thermostat temperature.

  • Should I turn my thermostat down at night?

No, the lower the water temperature will cause the use of more wood to recover.

  • What are the critical items to operate and maintain my furnace efficiently?

1. Keep water full

2. Manage ash

3. Use water treatment

4. Use seasoned wood

5. Keep fire in the middle of the firebox

6. Clean tubes regularly

Maintenance FAQs

  • Why is outdoor boiler water treatment important?

The boiler chemical (corrosion inhibitor) that you would apply to your furnace water coats the inside of the furnace to reduce the effects of corrosion on the metal. 

Click HERE to order our Liquid Armor Water Treatment and other outdoor wood furnace parts. Every gallon of Liquid Armor comes with FREE 2 sample bottles. Then submit your water sample to Outdoor Boiler Lab and get Free Water Test!

  • How often do I need to Inspect my Chimney/Flue

Inspect chimney and flue monthly and clean as needed. Clean chimney and flue annually. Perform cleaning and maintenance only when no fire is present in the firebox and ashes are cooled completely.

  • Why is ash management important?

If the ash becomes wet it is corrosive to the metal of the furnace. If the level of ash is too thick in the water box it does not allow for efficient heat transfer to the water in the water jacket of the furnace. The temperature of the water in the jacket is used to heat your house.


  • Why am I not getting hot water?

Check that the hot water system is connected properly. Check if the heat exchanger is partially or totally clogged.

  • Why does my furnace continue to burn when it is not operating?

Check the door seal, door adjustment, and solenoid.

  • I can't find a leak in my furnace. Why am I losing water?

Outdoor Wood Burning Boilers use a non-pressurized system, this means that the existing heating system is exposed to the air. Since the water in the system can and will be warmer than the air, there will be evaporation of the water in the system. The water must be checked and adjusted at least once a month, sometimes more.