definition a “backflow” is an undesirable
reversal of flow of a liquid, gas or
solid into the potable water supply.
A backflow preventer keeps this from
happening. Back pressure can force an
undesirable contaminant to enter potable
water piping. Sources of back pressure
may be pumps in the water distribution
system, boilers, heat exchanging equipment,
sprinklers and power washing equipment.
In these cases there may be an almost
constant risk of overcoming the static
water pressure in piping. To reduce
the risk of contamination, a backflow
preventer can be fitted. It is also
important when potentially toxic chemicals
are used, for instance for commercial/industrial
descaling (boilers or when bleaches
are used for residential power washing
and sprinkler systems.