With Open style radiant heating systems, the same water that circulates through your floor eventually comes out of your tap.
Eagle Mountain does not recommend using an open type domestic hot water heater system for hydronic heating. This type of system uses a domestic hot water tank as both your domestic hot water source and your heating fluid source.
The huge potential risk here is getting bacteria mixed with your drinking water due to the anti-scald and the auto-mix type faucets used today. They allow the hot and cold water supplies to mix at the faucet. This could introduce water that has been stagnating in a pipe in your floor into your drinking water.
Even if those types of “mixing” faucets aren’t used, the aerator screen and water path would still be exposed to the bacteria while running hot water, and then the bacteria could enter the cold water when it comes through the same path. We recommend using a closed system for all your radiant heating systems.