Cooling tower makeup and blowdown
Cycles of concentration, chemical dosing rates and evaporation credit on your water bill all depend on knowing makeup and blowdown flow. Most towers have a meter on one and nothing on the other.
Evaporation credit is worth measuring properly
Many municipalities will not charge sewer rates on water that evaporates rather than entering the sewer. To claim that credit you generally have to demonstrate makeup and blowdown volumes. Where the tower has a makeup meter but no blowdown meter, the claim is an estimate, and estimates get challenged.
Two weeks of logged data on both lines converts that into a defensible number. On a large tower the credit can run into five figures annually, which pays for a lot of rental weeks.
Cycles of concentration
Cycles equals makeup divided by blowdown. Run the meter on each line and you get the actual figure rather than the one the water treatment contract assumes. Towers running below their design cycles waste water and chemical; towers running above them scale.
Practical notes on tower piping
- Makeup lines are often plastic. Both meters handle plastic, but wall thickness entry matters more on plastic than on steel because the wall is a larger fraction of the signal path.
- Blowdown is intermittent. Log continuously rather than spot reading, or you will catch the line either fully flowing or fully still and neither represents the average.
- Outdoor installation. Tower piping is exposed. If the sensors will sit in a wet location, ask for the IP68 sensor option when you book.
- Low velocity. Makeup flow at a trickle can fall below the reliable measuring range on a large line. If the makeup pipe is oversized, expect poor readings at low demand.