If you have all of the fittings required by BCRWA, then the answer is no.  If you do not have a dual check valve the water can feed back out of your hot water heater which could cause damage. This can also occur if you have a leak between your dual check valve and the water heater. It is always good practice to turn the power off to the water heater any time your water is going to be off for more than a couple of hours.