The clear plastic tube mounted near the filter stack is a manometer. When the collector is running, the distance between the left and right columns of the manometer should be two inches or less. If it exceeds this, flow through the filter will be reduced and it must be cleaned. When the filter is clean, the back pressure will be less than 1.25". | The clear plastic tube mounted near the filter stack is a manometer. When the collector is running, the distance between the left and right columns of the manometer should be two inches or less. If it exceeds this, flow through the filter will be reduced and it must be cleaned. When the filter is clean, the back pressure will be less than 1.25". |