Which type of hydrotherapy tank would hold the largest volume of water?

The Hubbard tank is specifically designed to hold the largest volume of water among the options listed. This type of tank is typically used for whole-body immersion and is spacious enough to accommodate a person lying down or sitting comfortably within the unit. It is often utilized in therapeutic settings for various rehabilitation purposes, including facilitating exercises, providing hydrostatic pressure, and enhancing circulation.

In contrast, the extremity tank is smaller and intended for treating just a limb or extremity, making it unsuitable for larger volumes of water. The lowboy tank, although larger than an extremity tank, is still limited in volume and primarily used for lower body treatments, while the highboy tank is designed to accommodate treatments for the lower body as well but is still smaller than a Hubbard tank. Therefore, the Hubbard tank stands out as the clear choice when considering size and capacity for water volume in hydrotherapy contexts.