Installing an external wood-fired stove for your outdoor bath can be a game-changer—sustainable, relaxing, and delightfully rustic. For it to work efficiently and safely, the stove must be connected the right way. Below is everything you need to know for a proper setup and to avoid issues later on. For more on stove choices, see our comparison of heating types in hot tub heating methods and browse our range of external wood-fired hot tub stoves.
Understand How the Stove Works
External wood-fired hot tub stoves operate on a natural convection principle—no pump needed. Cooler water enters the stove, heats up, then rises back to the bath. Because circulation depends on gravity and heat, every connection and angle matters.
Know Your Connections
Your stove has two key connections:
- Lower connection: where cold water from the bath enters the stove.
- Upper connection: where hot water exits the stove and returns to the bath.
Reliable, natural flow depends on correct positioning and installation.
Installation Guidelines for Proper Function
Follow these essentials:
1) Position the stove close enough.
Keep the distance at 80 cm (or less) between stove and bath. Longer runs weaken convection and reduce heating efficiency. If you must go further, a circulation pump is required.
2) Maintain a slight upward angle.
The upper (hot-water) line must rise slightly toward the bath. A level or downward run can stall or reverse flow.
3) Secure and seal connections.
Tightly fit and properly seal all hoses/pipes to prevent leaks or air ingress that can disrupt circulation.
Why Getting It Right Matters
- Obstructed water flow: Incorrect slope or excess distance may stop circulation.
- Inefficient heating: Water warms very slowly—or not at all.
- Stove stress: Trapped hot water can increase pressure, which may damage or break the stove.
Final Check
- Is cold water entering via the lower connection?
- Does hot water return via the upper connection with a slight upward angle?
- Is the stove within 80 cm of the bath?
HowTo: Connect an External Wood-Fired Stove (Natural Convection)
- Place the stove: Position the unit within 80 cm of the bath.
- Attach the lower line: Connect the cold-water inlet from the bath to the stove’s lower port.
- Attach the upper line: Connect the hot-water outlet from the stove’s upper port back to the bath, keeping a slight upward slope toward the bath.
- Seal & secure: Tighten and seal all connections to avoid leaks and air entry.
- Do a dry check: Confirm distance, slope, and correct port mapping before first fire.
FAQ: External Wood-Fired Stove Connections
How far can the stove be from the bath?
Keep it within 80 cm to maintain strong natural convection. Beyond that, a circulation pump is required.
Which port is which?
Lower port: cold water from the bath to the stove. Upper port: hot water from the stove back to the bath.
Why must the upper line rise slightly?
Hot water naturally rises. A gentle upward slope supports continuous, pump-free circulation.
What happens if lines are level or sloped down?
Flow can stall or reverse, causing slow/no heating and potential stove stress from trapped hot water.
Do I need anything else?
Just tight, sealed connections and the correct layout.