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Guide
Wetbacks & Water Boosters Explained
A wetback lets your fire heat your hot water as well as the room. It can be worth it, but it isn’t right for every home or every fire.
How a wetback works
A wetback (also called a water booster) is a water jacket or coil in the firebox. While the fire burns, water from your hot water cylinder circulates through it and comes back hot. It needs a cylinder set up for a wetback, and the plumbing is done by a qualified plumber.
The trade-offs
- Heat that goes into the water doesn’t go into the room, so the fire heats the room a little less (Consumer NZ).
- Payback depends on your household: how much you use the fire, how much hot water you use and what you pay for power. With cheap firewood, Consumer NZ says a wetback can pay for itself over time.
- You still need another way to heat water when the fire isn’t lit.
- A water jacket cools the fire, so check the model’s emissions rating with its wetback fitted (Level, BRANZ).
Can a clean air fire have a wetback?
Yes, if that model is authorised with its wetback. The Ministry for the Environment says wetback burners still have to meet the national standard, and there are wetback models on the authorised list. Rural models (for properties over 2 hectares) often have more choice of booster size.
Not every fire can take one. Each fire page on our website shows a Water Booster line in its specifications: “optional” with any kW figure the maker gives, or “not available”.
Questions to ask before you choose one
- Is my hot water cylinder suitable, or will it need replacing?
- Where will the pipes run from the fire to the cylinder?
- Is the fire authorised with this wetback on my size of section?
- How often will we actually light the fire?
We’ll answer all of these at your free site check.
Sources
Official guidance we checked when writing this page (November 2026). Rules and fees change, so check the source or ask us before you rely on a figure.
Good to Know
Common questions
Does a wetback make the fire less efficient?
It takes some of the heat that would go into the room and puts it into your hot water, so room heating drops a little.
Do all wood burners take a wetback?
No. Check the Water Booster line in each fire’s specifications on our website, or ask us.
Questions?
Talk to a local expert
Free advice and an accurate installation quote from our team in Tauriko, Tauranga.