If you could, please send a link or sketch of the schematic of your
pumping arrangement with pipe diameters, run lengths, etc. Dual and
multiple pumping configurations require additional engineering
considerations to prevent pumps from fighting one another (basically
robbing water from one another) and to prevent sort circuiting water
backward through any pump that may not be working. I generally do not
like to specify pumps in parallel or series because even with careful
forethought such configurations can still present problems including
loss of prime & melted / leaking adjacent piping due to pump
overheating after a non-prime or no-flow situation. This is a
strategy I've seen used and recommend for dual (or multiple) pumps in
parallel drawing from the same suction line or manifold. First, all
the pumps should be identical -- same impeller and motor, etc. They
should be plumbed so they are hydraulically balanced on the suction
side and on the discharge side. Each pump discharge will need its own
check valve (normally mounted to flow vertically upward). Somewhere
downstream of all pumps, normally after the filter but prior to
chemical injection, tap X# of 1/4" or 3/8" tubing lines (X# = number
of pumps in parallel) and route each line to flow to a tap on each
pump discharge standpipe upstream of (prior to) the check valve. This
will encourage the working pump(s) to prime a non-prime pump. Since
you are installing check valves which may retain an entrapment vacuum
on the suction line a Safety Vacuum Release System (SVRS) device
should be installed on the shared suction line / manifold, especially
if a single drain sump. Dual pumps in series would require a bit more
info -- what is this booster pump for (chemical injection?). Having a
separate suction line from the main drain sump for each pump would be
a better engineered pumping configuration, but each pump suction may
require its own SVRS even without check valves. Terry Lambert PE,
tlamb...@yahoo.com.