These challenges included working with the existing subsoil substrate under the artificial turf. Most heated synthetic turf fields have a layer of sand several centimetres thick as a heat transfer base. In the case of TCF Bank Stadium, however, it was between 30 and 45 cm. The many cavities between the sand particles lead to a higher heat loss. Therefore, the individual heating circuits had to be installed closer to the field surface and the operating temperature of the heating medium had to be designed higher than conventional polypropylene or PEX pipes can achieve.

aquatherm blue pipe, on the other hand, can be used safely in applications from about -20 to 90 degrees Celsius (depending on the pressure rating) due to the multi-layer fibre composite material. The higher stability compared to other thermoplastic pipe systems ensures a trouble-free and durable function of the system even at high operating temperatures.

The use of aquatherm products also saved about 4000 mechanical connections, most of which were to be embedded under the pitch. Because aquatherm pipes and fittings do not depend on mechanical connections. Instead, they are permanently welded together by heat fusion. In the process, each welded joint becomes even more stable than the pipe itself after cooling.

Stable connections are particularly important when glycol-based heat transfer fluids are used, as the addition of glycol to water lowers the surface tension, increasing the likelihood of leaks. With aquatherm blue pipe the installers were able to transform several hundred pipe sections and thousands of fittings and manifolds into a seamless and durable pipe network.

Harris Mechanical was responsible for the installation of the piping. Despite the fact that no one from the company had ever worked with aquatherm products before, the team managed to install the entire pipe system within a few weeks after less than a day of practical instruction and passed the first official pressure test without a single leak. Justin Knopps, project manager for Harris Mechanical, liked the fact that the aquatherm pipe has a very low oxygen permeability and therefore does not require an oxygen barrier, which adds cost.

Given the tight schedule and overall complexity of the project, it was a great labor saver for the installers to be able to stick with one material for the entire system. Conventional thermoplastic systems are not universally available in all dimensions and would have required different types of joints between pipe materials. Knopps explained that these different connections between pipe materials were always going to be a problem for Harris Mechanical.

Several shell and tube heat exchangers, located in the adjacent heating center, serve as the heat source for the field. Over 26,000 litres of propylene-glycol mixture are pumped through the heat exchanger pipes, the supply lines and the individual heating circuits. The heat exchangers were designed to be 100% redundant, which means that even in the event of a total failure of the system, the reserve heat exchangers can cover the entire line required – because there must be no failures on match days.