Outdoor Wood Boiler Pump Size Matters

Outdoor Wood Boiler Pump Size Matters

Regarding outdoor furnaces, remember to have the correct size of your boiler pump. We carry two standard sizes of outdoor wood stove circulating pumps. The larger pump is the standard for installation and it is a 1/6 hp pump. This pump is strong and powerful and will handle most applications.

The smaller pump is only 1/25 hp and will work for some home installations if the distance between the outdoor wood furnace and the building is less than 75 feet and there are only 2 bottlenecks (such as one filter, and one heat exchanger). 

However, most home installations have three bottlenecks - a filter, a domestic hot water plate heat exchanger, and then a forced air heat exchanger. If you have three bottlenecks and/or more than 75 feet of distance, stay with the larger 1/6 hp pump. Both pumps are available through our online store HERE. You can also browse for more outdoor wood boiler parts.

So, when do you need MORE power than only ONE of our strongest 1/6 hp pumps? Good question. If you are pushing water more than 150 feet and going through more than three bottlenecks, you may need more power...BUT there is a right way to get that power and many wrong ways!

For outdoor boilers, DO NOT add a pump inside the building! This seems logical, but it does not work - this pump will get air locked and fail. Also, DO NOT think you can use a larger pump.

The PROPER way to get more power, is to "Daisy-Chain" together, the two of our special 1/6 hp hydronic circulators. Two pumps are "Daisy-Chained" together by simply connecting them to one another so they boost one another and provide the flow strength needed. And they must be located together at the back of the outdoor boiler so that they are always primed.

Also, make sure that your pump is always mounted so that the pump shaft is level to prevent an airlock as follows:

Boiler Pump Installation

If you have further questions, don't hesitate to contact the experts at OutdoorBoiler.com by clicking HERE.


  • 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!

  • 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 smoke come out through my door?

There are several adjustments that you can make to the door. Your door seal may be worn and need replacement. The seal usually needs to be replaced about every 3-5 years. It may be sooner if the wood is too close to the door in the firebox.

  • My Outdoor Wood Burner stopped running what should I do?

Check if there is there power to the furnace? Does the light work? Check the high limit switch? Is the blower and or solenoid working? Are the wires in good condition?

  • My Outdoor Wood Burning Boiler is leaking, What do I do?

Inspect the thermometer well, the aquastat well, the drain plug, the factory mounted feed plug, and the return cap, as well as any other fittings added in the field for leaks. Loose fittings are the most common cause of Leaky furnaces.

  • My Boiler Overheated?

We recommend that you evaluate the possible causes (listed below) and the corresponding solutions (also listed below) so that you can take the necessary steps to PROTECT your outdoor boiler from permanent damage.

Possible Causes:

  1. Door left open
  2. Pump failure
  3. The high limit switch cannot be reset
  4. Power outage/poor quality power
  5. Poor outdoor boiler door seal rope / Fan Seal
  6. Wood load too close to your outdoor wood burner front door
  7. Damper/Solenoid not closing properly

Click HERE for the complete information.

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