Surrey, BC

Since 1997

Used Hot Tub Shell Quality Considerations

By far the most common shells are made of acrylic with layers of fiberglass applied over it. The rough fiberglass provides the structural integrity, and the smooth acrylic skin is what gives it the colour and texture. 

Some fiberglass shells are better crafted, thicker and much stronger than others.

But pay attention to the acrylic part of the shell. There are different quality levels of acrylic sheets.  Some have antibacterial properties and wear better than others. Some are less porous, thicker and stronger than the cheaper alternatives.

Cheaper acrylics are more prone to fading, crazing, delaminating, cracking, blistering and splitting as it ages. Some are more easily damaged by UV rays and chemicals, and are more prone to “waterline etching”.

And it’s not just the quality of the acrylic that matters – it’s also how precisely and evenly the mold is pulled, how well the acrylic bonds to the fiberglass, how carefully the holes are bored, and how cleanly the sill perimeter is cut.

Poorly designed hot tubs and/or sloppy manufacturing techniques can result in the acrylic being over-stretched in certain areas, especially in the deep seats and floor corners. Sometimes the film is literally paper-thin and delicate. If water and/or air get between the fiberglass and the acrylic skin, it can begin to blister or delaminate. 


Rotomold Spas:

Rotomold hot tubs are made of a polymer (google it so I don’t have to compose an essay on the topic).  They’re cheaper to make but they are easily damaged by UV rays and extreme weather. They eventually start to crack as the oils in the polimer begin to deplete, causing the shell to shrink and pull. 

Some brands can be fixed by plastic welding, but others use polymers that cannot be welded once the rotomold shell cures.


Plastic Spas:

Some hot tub shells are made of plastic. Some claim that new technology makes them a viable option, but our experience so far has been that plastic is a terrible choice.


-with your fingers under the sill cut, pull up (hard) to see how strong the shell is (does it flex at all or is it totally stiff?)

-check the cut line along the bottom of the sill to see how thick the acrylic is

-Ask what the shell is made of (fiberglass is best).

-Ask what brand makes the acrylic sheet (Microban Antimicrobial is best)

-try find a speckled shell and check the tightest concave corners near the bottom of the shell to see how many dots per square inch there are compared to the sill area.  If the dots/speckles are visibly bigger and more stretched out in the deeper pockets, it’s an indication that the acrylic is thinned out in those areas – not a good sign.

-if colour doesn’t matter too much to you, go with the “sterling” (white marble) or “sierra” (grey speckled granite).  Those seem to wear the best.

-We recommend you avoid the pearlescent and metallic colours – they seem to be more vulnerable to chemical and UV attack and are more prone to fading and crazing down the road.