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ST108 Water Testing Protocols

Need to follow ANSI/AAMI ST108? 
ST108 sets water quality rules for medical device processing. Testing is how you prove you meet the standard. 

Talk to an ST108 Testing Expert

We’ll simplify what the standard requires, so you know exactly what to do. 

What You Must Do

Establish baseline water quality

Before you decide on equipment or changes, you need baseline testing. This gives you a clear picture of what’s in your water today and what problems exist. 

Performance Qualification (PQ) testing

AAMI ST108 describes a typical validation program as: 

  • intensive daily sampling and testing for a defined period 
  • at post-treatment test points and point-of-use test points 
  • against the quality criteria in the standard 

Continue routine monitoring

After PQ, ST108-style testing continues at a reduced frequency for at least one calendar year to find seasonal changes. 

Where Should You Sample

  • ST108-style sampling includes: 
  • Incoming water 
  • After each treatment step 
  • At points of use, including: 
      • Utility Water delivery points (washers / decontamination sinks) 
      • Critical Water points representative of water contacting devices 
      • Steam sampling at sterilizer delivery points 

What You Must Test

Below is a simple, practical list of what’s commonly tested for each ST108 water type, based on your ST108 testing reference. 

Utility Water — testing panel

Utility Water tests include: 
Chloride, Nitrate, Sulfate, Phosphate, Iron, Copper, Manganese, Zinc, Aluminum, Total Hardness, pH, Total Alkalinity, Color & Turbidity, Bacteria, Conductivity, Silicate. 

Critical Water — testing panel

Critical Water uses a stricter panel. Tests include: 
Chloride, Nitrate, Sulfate, Phosphate, Iron, Copper, Manganese, Zinc, Aluminum, Total Hardness, pH, Total Alkalinity, Color & Turbidity, Bacteria, Endotoxin, Total Organic Carbon (TOC), Conductivity, Silicate. 

steam boiler with multiple valves

Steam — testing panel

Steam testing includes: 
Chloride, Nitrate, Sulfate, Phosphate, Iron, Copper, Manganese, Zinc, Total Hardness, pH, Total Alkalinity, Color & Turbidity, Conductivity, Silicate, Aluminum. 

Note: Your exact plan depends on your system design and sampling points. The key is that you test the right water type at generation, after treatment, and at the point of use. 

Why Testing Matters for ST108 Compliance

Before choosing any equipment, testing gives you the data you need to make the right decisions and stay audit-ready. These four steps show how testing supports a stronger, clearer, and more compliant water program.

How it Works

Testing Tells You What Equipment You Actually Need

Before choosing any equipment, testing gives you the data you need to make the right decisions and stay audit-ready. These four steps show how testing supports a stronger, clearer, and more compliant water program.

Testing reveals the true condition of your water so you know exactly which equipment is required. It prevents overbuying by showing what you need—and what you don’t—to meet ST108 standards.

A complete ST108 program requires documentation of what you tested, where you tested, and when. These records show consistency and demonstrate that monitoring is being performed properly.

Facilities must track water data over time, identify trends, and record deviations and corrective actions. This ongoing documentation ensures long-term compliance and keeps you fully prepared for audits.

How ChemREADY Helps

  • Baseline testing
  • PQ testing plan + sampling map
  • Routine monitoring plan
  • Easy-to-read reporting + next-step recommendations

Choose Your ST108 Water Testing Package

We’ll help you select the right testing approach to confirm your current water quality, identify risks, and determine exactly what’s required to meet ST108 performance targets.

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Backed by decades of industry experience and a proven track record of results.

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Serving facilities across the midwest with responsive, local water treatment support.

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What to expect from a first conversation

  • We listen first — your situation, your timeline, your goals
  • We're honest about whether we're the right fit
  • If we're not, we'll point you to someone who is
  • No high-pressure close. Ever.
  • 30 minutes. You'll know if it makes sense to continue.

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