SaunaLife Model S4B Black Wood-Burning Hot Tub

The Model S4B delivers the same brilliant engineering as the S4N in a bold black finish that makes a statement in any outdoor setting. The self-cleaning corrugated 304 stainless steel stove with secondary combustion chamber captures heat from exhaust smoke, reducing wood consumption by up to 50% compared to traditional wood-fired hot tubs. The stove draws cooler water through a lower channel and redistributes it through an upper channel to equalize temperature throughout the tub, while the air gap between the fiberglass interior lining and the Thermo-Spruce exterior is super-heated to accelerate the warm-up process — producing the fastest heat-up time in its class. The ergonomically shaped dark grey fiberglass interior comfortably accommodates up to 6 bathers, and the 1.65" thick black-painted Thermo-Spruce surround lasts up to twice as long as cedar while delivering a bold, contemporary outdoor aesthetic. Matching Thermo-Spruce steps, an extra-thick steel-reinforced foam cover with dark grey marine-grade vinyl exterior, a polished stainless steel chimney with cap, and an integrated drainage tap are all included. No electricity, no chemicals, no installation required.

Key features

• Fully assembled, no installation or electrical connection required
• Heats 304 gallons from 40°F to 95°F in 1.5 to 2 hours
• 304 stainless steel wood-burning heater with dual heat compartments
• Self-cleaning corrugated stove with secondary combustion chamber, up to 50% less wood consumption
• Black-painted Thermo-Spruce tub surround, lasts up to 2x longer than cedar, 1.65" thick
• Superior thermal R-value to retain heat longer
• Dark grey contoured fiberglass interior, comfortable for up to 6 bathers
• Polished stainless steel chimney with chimney cap
• Extra-thick steel-reinforced foam cover, folds for easy removal and storage
• Dark grey marine-grade vinyl cover exterior
• Matching Thermo-Spruce steps included
• Integrated hot tub drainage tap
• Eco-friendly, no electricity, no chemicals required
• Designed by SaunaLife, handcrafted in Northern Europe
• 2-year limited warranty (consumer use)

Brand: SaunaLife
Model: MODEL S4B
Material: Black Thermo-Spruce
Capacity: Up to 6 persons
Water Capacity: 304 gallons
Maximum Temperature: 106°F (41.1°C)
Heat-Up Time: 1.5 to 2 hours (40°F to 95°F)
Interior Dimensions: 71" Diameter x 33"H (180.3 x 83.8 cm)
Exterior Dimensions: 79" Diameter x 37"H (200.7 x 94 cm)
Stove Dimensions: 19.8"W x 11.8"D x 13.1"H
Chimney Height: 95"H (241.3 cm)
Maximum Wood Length: 16" (40.6 cm)
Product Weight: 441 lbs (200 kg)
Filled Weight: 2,976 lbs (1,349.9 kg)
Stove Material: 304 stainless steel
Warranty: 2-year limited (consumer use)

Fully assembled black Thermo-Spruce wood-burning hot tub

Matching Thermo-Spruce steps

Extra-thick steel-reinforced insulated cover

Integrated drainage with tap

Polished stainless steel chimney with chimney cap

Installation instructions

2-year limited warranty

The Model S4B arrives fully assembled; no installation or electrical connection required. Place on a firm, level outdoor surface with adequate drainage access. Fill with water before lighting the stove. Use wood no longer than 16" in the stove and follow the included installation instructions for fire management and safe operation. Note: filled weight is 2,976 lbs; ensure your surface can support this load. The integrated drainage tap makes emptying straightforward. The folding insulated cover retains heat between sessions and should be removed before use.

• Installation Manual
• Dimensions

2-year limited warranty (consumer use). Covers manufacturing defects in materials and workmanship under normal residential use. Does not cover normal wear and tear, damage from improper installation or misuse, cosmetic damage, unauthorized modifications, or shipping damage reported after 48 hours. Contact support@marterraelements.com with your order number, photos, and a description of the issue. We aim to respond within 2 to 3 business days. Warranty is non-transferable and requires original proof of purchase.

• Saunalife Warranty

$950 flat rate freight to the contiguous United States. Remote or complex delivery areas may not qualify for this rate. Delivery is by special appointment on a wooden pallet encased in wood for solid protection; we will contact you prior to shipping to share delivery details and discuss any circumstances that may affect the process. Standard delivery is curbside only; the driver lowers the item to ground level but is not responsible for moving it to its final location.

Returns are accepted within 30 days of delivery and require prior approval before anything is sent back. Please reach out to support@marterraelements.com to get the process started. Items must be unused, undamaged, and in their original condition with original packaging intact. For additional details, please visit our Return & Refund page.