The Auxiliary Heater Bypass Loop is an optional plumbing configuration available on select Hydropool swim spa models, including the AquaTrainer. It’s built for owners who want to add a supplemental heat source — typically an external heat pump — to help maintain temperature, especially useful for extending swim season in colder climates or larger swim spas that take more energy to heat.
The “bypass” part is the key detail: the loop is plumbed so water can route around the primary heater when it isn’t needed, rather than forcing all water through it regardless of demand. That keeps water flow efficient and reduces unnecessary wear on the main heating system, since it isn’t working overtime to compensate for supplemental heating elsewhere in the loop.
This is a plumbing option specified at the time of purchase or installation, documented in Hydropool’s swim spa owner’s manuals, and worth a conversation with your dealer if you’re planning to run an auxiliary heat pump alongside your swim spa’s standard heater.
Source: Hydropool Swim Spa Owner’s Manual (hydropoolhottubs.com) and AquaVision Pool & Spa’s Hydropool feature page.