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.
The flow rate of the water is most likely determined by the flow rate of the faucet or fixture. At only 40 psi a 1/2 diameter copper pipe 100 feet long would have a flow rate of over 6 gallons per minute with a velocity through the pipe of over 10 feet per second. At that rate your hot water would arrive at your sink in about 5 seconds! Large diameter pipes would have even higher flow rates.