Suction strainers truly affect pump performance - there is no debate on that. Each manufacturer's suction strainers produce different flow capabilities. Regardless of the flow capabilities of these strainers, when strainer intake screening is missing, no strainer is going to work very well. At this flow testing drill in New Hampshire several years ago, we found out that it pays to check the strainer before using it. A good reminder to regularly inspect all tools and equipment.
A low level strainer getting ready to be flow tested.
At fist glance, the strainer looks to be okay.
A fire pump's suction inlet screen is the "last line of defense." When the suction strainer being used at this flow test had some intake screening missing, leaves were able to be sucked up into the suction hose - thus causing a problem at the pump's suction inlet.
Notice the missing "screening" on this side of the strainer.
Screening is in place on this side of the strainer.
