Does wall thickness affect spa durability?
The acrylic provides color, not structure. We measure durability by weight and the thickness of the fiberglass, not thickness of the acrylic. The acrylic covering is at most 1/8 inch thick and tapers to 15 or 20 thousandths of an inch in the foot well of the spa. Water is heavy. Water in a spa can weigh one or two tons. What happens when you fill a thin walled spa with water? The water pushes down and gradually bends or breaks the spa. To compensate for the lack of strength in a thin-walled spa, some manufacturers fill the underside with urethane foam. Others require sand or a wood structure underneath the spa. Sand or foam provides support under the benches or seats, lounger area and step. Portable spas often depend on the wooden skirt to support the water. Without the skirt, many of these cheap spas would collapse. If the spa shell is thick enough, no other reinforcement is necessary.
