Spa Fitter
Celtic Hot Tubs Mystic 236 Replacement Cover
The Celtic Hot Tubs Mystic 236 takes the AIRCAP 1™ XX-Small — a foam-free replacement hot tub cover for square spas 77"–79". The Mystic 236's cabinet measures 78" x 78", inside the XX-Small's range. The cover weighs 35–40 lb for life, costs $1,195, is engineered to comply with ASTM F1346-23, and carries a 3-year limited warranty.
| Spa cabinet | 78" x 78" |
|---|---|
| AIRCAP 1™ size | XX-Small fits 77"–79" |
| Cover weight | 35–40 lb — constant for life |
| Price | $1,195, free US shipping |
| Skirt | Ziptech™ modular, three lengths included |
| Safety | Engineered to comply with ASTM F1346-23 |
| Warranty | 3-year limited warranty |
Why the XX-Small fits the Mystic 236
The AIRCAP 1™ comes in six sizes covering square spas from 77" to 94". Each size is built to overhang its band slightly — that is how a spa cover is meant to sit — so the XX-Small, which fits cabinets 77"–79", covers the Mystic 236's 78" x 78" shell with the right overhang.
At 78" the Mystic 236 sits mid-band in the XX-Small's 77"–79" range, 1" off the bottom and 1" off the top. Within Celtic Hot Tubs, the Mystic 236 shares that 78" x 78" cabinet with Mystic 118, Mystic 118RS (Mystic Special Edition), Mystic 120 (2025 and earlier) and Mystic 120S — same footprint, same cover. The 11 Celtic Hot Tubs models we fit sit on 2 footprints, and the Mystic 236 is on the smallest of them; together they span 2 of the six AIRCAP 1 sizes.
Cabinet dimensions can change between model years. Before ordering, measure your Mystic 236 at its widest point across the top, in both directions, including any acrylic lip that overhangs the cabinet — the SureFit™ guide walks through it in two measurements. If a figure you have found elsewhere is larger than ours, an overhanging lip is the usual reason. If your spa measures between two sizes, round up.
Every spa in our catalogue that measures 78" x 78" is on one page: hot tubs that take a 78" × 78" cover — the same AIRCAP 1™ XX-Small, at the same price.
How the AIRCAP 1™ is built
Instead of a rigid foam core wrapped in vinyl, the AIRCAP 1™ uses welded drop-stitch construction: a sealed air chamber with no foam to absorb water, so it does not become the waterlogged two-person lift that ends most foam covers. More on how it insulates, how it holds up, and why it is foam-free — or estimate what your current foam cover weighs.
Every Celtic Hot Tubs model we fit
| Model | Cabinet | AIRCAP 1™ |
|---|---|---|
| Mystic 118 | 78" x 78" | XX-Small same cover as the Mystic 236 |
| Mystic 118RS (Mystic Special Edition) | 78" x 78" | XX-Small same cover as the Mystic 236 |
| Mystic 120 (2025 and earlier) | 78" x 78" | XX-Small same cover as the Mystic 236 |
| Mystic 120S | 78" x 78" | XX-Small same cover as the Mystic 236 |
| Mystic 126 | 78" x 78" | XX-Small same cover as the Mystic 236 |
| Mystic 236 (this page) | 78" x 78" | XX-Small |
| Clover 124 | 84" x 84" | Small |
| Clover 130 | 84" x 84" | Small |
| Clover 240 | 84" x 84" | Small |
| Clover 250 (2025 and earlier) | 84" x 84" | Small |
| Clover 250S | 84" x 84" | Small |
Celtic Hot Tubs Mystic 236 cover: common questions
What size hot tub cover fits the Celtic Hot Tubs Mystic 236?
The Celtic Hot Tubs Mystic 236 takes the AIRCAP 1 XX-Small, which fits square hot tubs measuring 77"–79" across. The Mystic 236's cabinet measures 78" x 78", inside that band. Measure your spa side to side across the top of the cabinet to confirm before ordering.
Will the AIRCAP 1 fit a Celtic Hot Tubs Mystic 236?
Yes — the Mystic 236's 78" x 78" square cabinet falls in the AIRCAP 1 XX-Small's 77"–79" range, and the Ziptech modular skirt system ships with three skirt lengths so the drop over the cabinet adjusts without a custom order. Cabinet sizes can change between model years, so confirm with two quick measurements.
How much does a replacement cover for the Celtic Hot Tubs Mystic 236 cost?
The AIRCAP 1 costs $1,195 in every size, including the pump, three Ziptech skirt lengths, and tie-down straps, with free US shipping and 30-day returns. Unlike a foam cover it has no foam core to waterlog, so it stays at its original 35–40 lb weight for life.
How heavy is a replacement cover for the Celtic Hot Tubs Mystic 236?
The AIRCAP 1 XX-Small weighs 35–40 lb and keeps that weight permanently — its sealed drop-stitch air core cannot absorb water. A foam cover starts at 40–75 lb and gains weight as the foam saturates.
Not a Mystic 236?
The Spa Fitter matches the current models of every major brand to the right AIRCAP 1™ — or measure any square spa with SureFit™.