Gorman-Rupp Pumps 3D-B 883512 and up - Manual (Page 7)

D SERIES OM−01490
PAGE A − 2 WARNINGS
Never install a positive shut-off valve in the
discharge line; discharge restrictions will
cause excessive friction loss resulting in
overloading and destruction of pump and
drive components. It is strongly recom-
mended that unless absolutely necessary,
no positive shut-off valve be installed in the
suction line; excessive restriction will
cause incomplete filling of the diaphragm
chamber and result in shortened dia-
phragm life.