"Rob Reali" wrote
No pump needs an air tank, however, the captive air tank is a great
option
as it allows the pump not to have to cycle on and off for small,
occasional
uses.

ummmm not really. All pump/motor manufacturers want a minimum rest
period of 60 seconds between starts for motors up to 1.5 hp; And over
1.5 hp it's 120 seconds. Water is basically unable to be compressed. So
since the pump would start as soon as water was used, it would also
build pressure all but instantly and shut off if the fixture being used
can't handle the flow the system delivers to the fixture. That would
cause an instant drop in the pressure and the pump would come on again
to repeat this over and over while the pressure fluctuated drastically
but, and here's the real problem, this would cause the system to
experience and be damaged by water hammer. Probably until something
broke and a pressure tank was installed, if only a 1.5 gallon tank that
would act like a water hammer arrestor but also allow the pump to stay
off for some time while water was used in small volumes. Also as
important as water hammer problems is that without a pressure tank, the
pump motor would likely as not burn out in a short period of time due to
not being able to cool sufficiently between starts.

Gary
Quality Water Associates