[Retlaw]

Originally Posted by Neil

I thought the loop was to comply with water regs so you cant get nasty boiler water into your drinking water.

I wonder if they have a double check valve.

Because the domestic supply pressure is usually greater than the boiler will stand, and dometic water pressure is not constant.
During the night the water pressure on fire hydrants is a heck of a lot greater that during the day.

Retlaw.