Sand filters must be periodically backwashed in order to loosen up the sand and to eliminate filtered dirt through the waste system. This requires, among other things, the hydraulic current of...

Sand filters must be periodically backwashed in order to loosen up the sand and to eliminate filtered dirt through the waste system. This requires, among other things, the hydraulic current of...

Sand filters must be periodically backwashed in order to loosen up the sand and to eliminate filtered dirt through the waste system. This requires, among other things, the hydraulic current of...

Sand filters must be periodically backwashed in order to loosen up the sand and to eliminate filtered dirt through the waste system. This requires, among other things, the hydraulic current of...