Acrylic Spa Shells
When shopping for a hot tub it is critical to purchase a tub with a quality shell that will last for the life of your tub. This is so important since in most cases the life of the shell IS the life of the hot tub. So the question for me became why are so many shells cracking?My service days for acrylic spas were during a time in the industry when there was rapid growth and consumer interest as well as many new manufacturers in the industry. During this period many different shell construction techniques were created, tried and abandoned due to a lack of reliability.
Common Spa Shell Materials
Acrylic, resin, plastic, fiberglass, ABS, PVC, CPVC and poly urethane shell compositions and interior finishes were all explored. The industry has now stabilized to a small degree and most tubs built today have an acrylic interior finish with an ABS backing permanently adhered. This provides a smooth interior finish that is durable and comfortable.
Acrylic Is The Finish - What Is The Rest?
Pretty much any hot tub that you can find for sale today has an acrylic interior finish. As my clients had indicated to me time and time again, all hot tubs look the same despite huge price variations. I had expected to find subtle differences that the average consumer would never see, being a hot tub construction specialist that is, but I was surprised at what I found beneath the shiny acrylic surface.ABS Laminated Acrylic Spa Shells
The thickness of the shell is a huge contributing factor in shell failure, as is the choice of backing material used. 95% of acrylic hot tubs are foam filled which I had initially assumed was for heat retention purposes. As it turns out the foam is used as a structural support for the acrylic shell. This style of shell uses an ABS backing material attached to the acrylic interior surface.About half of these tubs stop at this point and use foam to hold the structural shape and these comprise the lowest quality spa shells currently commercially available.
Fiberglass Laminated Acrylic Spa Shells
The other half of these hot tubs will have fiberglass rolled over stress points on the ABS backing adding additional rigidity. This is required most especially in areas such as the foot well which will be under the most pressure from water and bather weight forces. This helps to add strength to known areas prone to failure. Better quality than no fiberglass at all, this superficial coat of protection did not meet my standard for quality.How To Instantly Spot A Quality Spa Shell
To discover the quality of a hot tub shell you need only ask for the warranty information about it. This is a clear indication of how confident that manufacturer is in their product. During my research I encountered warranties for the structural shell starting at three years on the low end with five and seven year warranties being industry standard. I did encounter a ten year structural shell warranty for one tub which was good but I wanted more.I wanted to see a lifetime warranty on the structural shell of any hot tub that I would recommend to my clients. As it turns out there is a company that does have a lifetime guarantee on the shell. Upon inspection of this hot tub I found a solid fiberglass backing on the acrylic finish. Essentially is is built like a boat hull and is substantially stronger than ABS backed with fiberglass patches. The solid fiberglass hull construction instead of ABS backed with a thin layer of fiberglass is a clear cut winner in terms of strength, and in my opinion quality as well.
Avoid The Worst Case Scenario Spa Failure
Especially from my service technician point of view, when I think of what potential hot tub problem I want to avoid the most, I instantly think about the shell. A failed shell on an out of warranty hot tub is heartbreaking and terminal in most cases for the spa. This alone pretty much made up my mind as to what I would recommend my clients to purchase.Ideally I want to build a concrete hot tub to compliment the swimming pools that I build for my clients. In a circumstance that a concrete spa is outside of the budget constraints I enjoy the confidence in endorsing an acrylic hot tub with a lifetime guarantee on the shell. If anything breaks I know that if all else fails I can service and repair the tub myself but I do not want to deal with a broken shell.
It was while researching the shell of the hot tub that I discovered something that surprised me. The single most common reason for hot tub failure was from freezing, which I learned was not from a lack of insulation, but a flawed approach to cold weather operation and freeze protection on models sold in Canada.
Proceed to the section that deals with Spa Insulation