During bottle washing, the concentration of detergent in the wash tank will decrease during the day. This is caused by the bottles taking out detergent as they pass through the wash section and is known as “drag out”.
With some machines the drag out can be considerable, so that by lunchtime the concentration may be half of the original. In hard water situations this can lead to ineffective washing and scale build-up on heater elements. The loss of detergent should be compensated throughout the day.
There are several ways of doing this, the most basic being to top up the detergent manually. Other methods involve automatic addition via a pump. This may be through timed addition, where the pump adds detergent in increments throughout the day, or by closed loop addition where the pump is linked to a conductivity probe. The pump will activate when the conductivity (concentration) falls below a set threshold.
If you do not want to invest in additional equipment, a simple top-up chart can be provided which shows how much detergent needs to be added at different conductivity levels. Low-cost pocket conductivity meters are available from several suppliers for measuring the conductivity at regular intervals throughout the day