Key facts
| Octagram | Zen Bathworks round tubs | |
|---|---|---|
| Price | $7,500, stove and cover included | Tub only from $9,819 (5 ft), $10,860 (6 ft), $11,969 (7 ft) with 29 in walls |
| Build | 1/8 in welded marine-grade aluminum, cedar sheathing | Western Red Cedar heartwood staves |
| Size | 5 ft across, 3 ft deep, eight-sided | 5, 6 or 7 ft round; 29, 36, 42 or 48 in walls |
| Water | About 300 gallons | 260 to 940 gallons by size and wall |
| Heat | Submersed aluminum wood stove only | Electric 11 kW (+$2,350), gas (+$4,970), wood-fired Chofu (+$1,499) or Timberline (+$6,499) |
| Power needed | None | None for wood; a 240V circuit or gas line otherwise |
| Made in | Midcoast Maine (maker statement) | Haines, Alaska (maker statement) |
| Lead time | Made to order, 4 to 6 weeks | Ships as a crated kit or pre-assembled |
Sources: Octagram product page; Zen Bathworks 5 ft, 6 ft and 7 ft product pages. Prices checked October 24, 2026, and can change.
Off-grid simplicity vs a configurable tub
The Octagram has no pump, filter or cord. You fill it, light the submersed stove and wait. That suits a cabin, a beach lot or a backyard where running a circuit would cost more than the tub. Everything you need comes in the box: stove, 5 foot stove pipe, chimney cap, drain with a ball valve, ash shovel and a cedar cover.
Zen Bathworks sells the tub and the heat separately. The 5 ft, 6 ft and 7 ft round tubs come in four wall heights, and you choose a wood stove, an electric spa pack or gas. Jets are optional. An electric or gas pack adds digital controls and freeze protection, which matters if you want hot water on a weeknight without tending a fire.
Size and weight
The Octagram seats two comfortably and three to four close together. Zen's 7 foot tub with a 48 inch wall holds 940 gallons, more than three times the water. Water weighs about 8.34 lb per gallon, so filled weights climb fast:
| Tub | Gallons | Water weight |
|---|---|---|
| Octagram | About 300 | About 2,500 lb, plus a 200 lb tub |
| Zen 5 ft, 29 in wall | 260 | About 2,170 lb |
| Zen 6 ft, 36 in wall | 495 | About 4,130 lb |
| Zen 7 ft, 48 in wall | 940 | About 7,840 lb |
Add people and the tub itself. A deck rated for typical live loads may not carry the larger sizes, so read our deck weight guide before choosing a spot. A gravel or concrete pad on level ground is the simple answer.
Cost once it is running
A wood-fired tub's running cost is firewood and your time. An 11 kW electric pack on a Zen tub heats faster than a typical plug-in spa heater but draws much more power while it runs, so look up your utility's rate before choosing it. Gas avoids the big circuit but needs a gas line, which usually means a permit.
Burn bans and smoke rules
If wood is your only heat, local air rules matter. In the Puget Sound region, Stage 1 and 2 burn bans prohibit outdoor wood fires, which would idle a wood-only tub on those days. Oregon and other western regions run similar curtailment programs. See our guides to Washington burn bans and Oregon burn restrictions. A Zen tub with an electric pack keeps working on ban days.
Which to pick
- Octagram: off-grid, two to four people, one price with everything included, and you enjoy tending a fire.
- Zen Bathworks: a classic cedar stave tub, room for more people, and the option of electric or gas heat for year-round use.
Related guides
- Plug and play 120V vs 240V hot tubs
- Hot tub disconnect and GFCI rules
- Wood-burning sauna stoves in Washington and Oregon
Frequently asked questions
What is the difference between the Octagram and a Zen Bathworks cedar tub?
The Octagram is a welded marine-grade aluminum tub wrapped in cedar, heated only by a submersed wood stove, with no power at all, for $7,500. Zen Bathworks builds traditional Western Red Cedar stave tubs in 5, 6 and 7 foot sizes, sold as the tub alone from $9,819, with your choice of electric, gas or wood-fired heat added.
How much water does a wood-fired hot tub hold?
The Octagram holds about 300 gallons. Zen Bathworks lists 260 to 460 gallons for its 5 foot tub depending on wall height, 390 to 685 for the 6 foot and 530 to 940 for the 7 foot.
How heavy is a filled wood-fired hot tub?
Water weighs about 8.34 lb per gallon. The Octagram's 300 gallons is about 2,500 lb of water plus a roughly 200 lb tub, before people. A 7 foot Zen Bathworks tub with a 48 inch wall holds 940 gallons, about 7,840 lb of water. Both belong on a level, solid base.
Can a Zen Bathworks tub run without electricity?
Yes, if you choose a wood-fired heater. Zen Bathworks offers a Chofu wood-fired heater (+$1,499) or a Timberline (+$6,499). It also offers an 11 kW electric spa pack (+$2,350) and gas (+$4,970) for push-button heat with freeze protection.
Are wood-fired hot tubs affected by burn bans?
They can be. Puget Sound Clean Air Agency Stage 1 and 2 burn bans prohibit outdoor wood fires, and other regions have similar curtailment days. Check the rules for your area before relying on a wood stove as your only heat source.
Where are the Octagram and Zen Bathworks tubs made?
Octagram states its tubs are designed and built in Midcoast Maine. Zen Bathworks states its tubs are handcrafted in Haines, Alaska.
Keep reading
Browse our hot tubs collection, see all guides, or ask us a question about your project.