Most people believe that if something costs more, it has to be better quality. In the case of generic drugs, this is not true, says Gary Buehler, Director of FDA's Office of Generic Drugs. The standards for quality are the same for brand name and generic products..uch of FDA's review of generic drugs and brand name drugs is the same, Buehler explains (See Same FDA Requirements for Brand-Name and Generic Drugs below).
Then evaluate tank water heaters on the same gph basis to determine how many gallons of storage are needed to meet this demand. While tankless water heaters do not run out of hot water, if not sized correctly, the flow rate of that water can be adversely impacted.
Quick Answer. To calculate the water flow rate, square the pipe's diameter, and then multiply that number by pi, .25 and the velocity of the water flow. For example, a pipe with a diameter of 3 inches, or .25 feet, and a water velocity of 20 feet per minute yields a flow rate of approximately 0.98 cubic feet per minute. Convert this number to the unit of measure for residential flow rates to yield a final answer of 7.34 gallons per minute.