Washer Dosing Systems
Washer disinfectors are complex machines with many interconnected systems. One of the most critical components used for proper cleaning is the chemical dosing system. Although it is physically small, this system has a major impact on washer performance and the reliability of cleaning results.
The dosing system often goes unnoticed until something goes wrong. At the same time, it is one of the parts of the washer that users interact with most, especially when changing chemistry. A basic understanding of how this system works can help staff avoid problems, improve cycle consistency, and keep the washer running with less downtime.
How Chemical Dosing Systems Work
Most washers use one of three approaches to deliver detergent:
• Time-based dosing: The pump runs for a set time and delivers a fixed volume of detergent.
• Impulse-based dosing (flow meter controlled): A flow meter measures the actual volume of detergent for greater precision.
• Hybrid systems: A combination approach that uses elements from both time-based and impulse-based systems.
Each system has advantages and disadvantages, but all of them depend on three key factors: good tubing condition, reliable dosing pumps, and proper calibration.
Dosing System Calibration
Calibration ensures the machine delivers the correct amount of chemical during a cycle. It is necessary no matter what type of dosing system is used and should be performed routinely or whenever components are replaced.
Calibration helps correct for common issues that can impact dosing such as:
• Chemical tubing that has become worn, hardened, or clogged with residue
• Flow meters becoming blocked or fouled
• Pumps degrade and become less efficient over time
Without regular calibration, a system that appears to be functioning may be delivering the incorrect amount of chemical. Underdosing risks ineffective cleaning, while overdosing can cause foaming, leave chemical residue, and waste expensive detergent.
Calibration should also be performed any time changes are made to the system. Switching detergent types or brands, extending the length of suction lines, or replacing dosing components all change the way the system performs and can lead to inaccurate dosing if not corrected.
Impact of Air in the Dosing System
One of the most common reasons for dosing problems is air entering the system, usually when detergent bottles are changed. Even a small pocket of air in the line can interrupt suction, cause inaccurate dosing volumes, or trigger flow meter errors.
• In time-based systems, air can prevent detergent from being consistently pumped to the washer, resulting in underdosing and poor cleaning outcomes.
• In impulse-based systems, air bubbles can cause disruptions in flow triggering errors that result in alarms.
Best practices to avoid air entry:
• Always keep suction tubing fully submerged in chemical
• Keep detergent lances upright when changing bottles
• Prime chemical lines whenever possible after a bottle change
• Train staff on correct bottle replacement techniques to prevent introducing air into the system
Preventing air entry is one of the simplest and most effective ways to reduce unnecessary service calls.
Summary
The dosing system may be small, but its role is big. When dosing is inaccurate, it affects every part of the washer’s performance. Inconsistent cycles lead to reprocessing delays, wasted chemicals, and additional strain on staff who must troubleshoot failed loads. Most importantly, it increases the risk of instruments not being adequately cleaned before sterilization.
By focusing on proper calibration, monitoring tubing condition, and preventing air entry during chemical changes, SPD staff can keep dosing systems working as intended. These small steps protect the washer’s performance, reduce downtime, and help ensure instruments are safe and ready for patient care.