What Type of Water Should I Use for My Outdoor Furnace?

What Type of Water Should I Use For My Outdoor Furnace

“What type of water should I apply to my boiler?”

“Can I use deionized water in my boiler water tank?”

These are just two of the common questions that we get from customers who own an outdoor wood-burning boiler. Some would ask if they could apply well water, rainwater, etc.

Outdoor Boiler Water treatmentWhat Type of Water Should I Apply to My Boiler?

The answer is ONLY PROPERLY TREATED water is allowed and should be applied to your outdoor boiler. It is essential for all outdoor furnaces and one of the most critical things that you should consider when you have an outdoor wood stove.


Good question! Companies that manufacture outdoor wood furnaces use mild steel, high-grade steel, and stainless steel in their outdoor furnaces. However, if untreated water is utilized, even high-grade metal can corrode. Remember that water starts to eat holes in steel immediately upon contact (through rust corrosion) UNLESS the water is properly treated with a special chemical that has been formulated to protect the exact grade of steel in your furnace.

Your outdoor boiler runs great, doesn’t it? But do you know what it looks like on the inside? We have seen the inside of MANY outdoor boilers, and if you don’t use water treatment, this is what it looks like:

Rust Steel

Going back to the question above, “Can I use deionized water in my boiler water tank?”.

The answer is yes, if and only if, you have applied water treatment.

What is the Best Water Treatment Corrosion Inhibitor for My Outdoor Wood Boiler?

Liquid Armor is the #1 Outdoor Boiler water treatment because it has been specially formulated to protect the exact grade of steel in your outdoor boiler!

See PROOF! In this video about outdoor boiler water treatment, we explain how customers who use Liquid Armor Water Treatment in their boilers will protect their investment better than any other way:


Best Outdoor Boiler Watert Treatment

Treating the water in your outdoor boiler with safe and effective Liquid Armor water treatment is the most important thing you can do to protect your furnace.

You cannot see the inside of your water jacket unless you have a cutting torch and cut open a hole in the steel. But...

But we have seen the inside of many water jackets.

For those who use Liquid Armor Boiler Water Treatment, the inside of their water jacket looks like this:

Stainless Steel

What Is The Easiest Way To Add Water To An Outdoor Boiler?

Most of our customers already know the answer to this question - you simply open a valve in the basement and watch the boiler until water comes out of the vent tube at the top. This system incorporates a kit we call the "In-House Fill Kit".

Fill Kit Assembly


Fuming madThe In-House Fill Kit allows you to add water to your boiler by opening a valve that connects the domestic water supply to the boiler loop - IN YOUR BASEMENT! Without this kit, the boiler must be filled using buckets of water you carry to the boiler or a hose that you have to drain each time so it does not freeze - what a pain that would be!

This system uses a backflow preventer to keep your domestic water supply safe. You would never want outdoor boiler water to backflow back into your domestic water supply and come out of your sink or shower. Our system prevents that perfectly. Also, our system meets the codes that are required to keep domestic water systems safe.

So all you do is open the valve for a few seconds and PRESTO! your outdoor wood boiler is full again. Remember to bypass any water softeners if you are filling the boiler for the first time.

How Much Water Treatment Should I Add?

For the first-time treatment, one gallon of Liquid Armor will treat 200 gallons of water. This is a generalization because water quality is widely different around the country – this is why the FREE water testing is so very important.

For a boiler that has been properly treated previously, just add one-half gallon every 12 months before sending your annual water sample.


It is never too late to start protecting your investment!! Liquid Armor Certified Water Treatment is the only way to treat your boiler – Liquid Armor has been formulated to protect the exact grade of steel in your boiler. Just start now and stop the rapid destruction of your steel. If you do this, you can Keep Your Family Toasty Warm and Comfortable for Decades.

For more information about our FREE Water Testing CLICK HERE or contact OutdoorBoiler.com.