Geosil50: The Legionella Biocide

Geosil50 is a Silver Peroxide biocide boosted with silver.

This environmentally sustainable water treatment product has proven efficacy in controlling Legionella in water distribution systems. Geosil50 breaks down into water and oxygen, leaving no harmful residues or odours.

How it works

Geosil50’s powerful oxidising agent – hydrogen peroxide – reacts with organic matter by breaking apart cell walls, damaging its DNA and enzymes to eventually destroy it.

Ionic silver assists the disinfection process by increasing the susceptibility of bacteria to the effects of the oxidising agent. The positively charged silver ion is drawn to bacteria, boosting the exposure of that bacteria to the peroxide and, in the process, increasing the biocide’s effectiveness.


Approvals and certificates

Geosil50 has been granted Biocidal Products Regulation Approval (BPR) and is authorised for use against Legionella.

To meet the approval, we undertook rigorous field testing according to the ECHA Guidance (Guidance on the Biocidal Products Regulation Volume II Efficacy – Assessment and Evaluation (Parts B+C) Version 3.0 April 2018), and Section on disinfection of inner surfaces in human drinking water systems.

The application was registered by the European Chemical Agency (ECHA) and assessed by the Health and Safety Executive (HSE).

Chlorine Products vs. Geosil50

The widely used alternative to treatment with Geosil50 is chlorination. From the comparison table below, it is clear to see why Geosil50 is the best and most effective water treatment in the market:


Effective pH range

Harmful Breakdown Residue


Shelf Life

Environmental Footprint





6 months

x3 volume





2 years

x1 volume

Disinfection Procedure

Geosil50 is approved for professional water treatment of water storage tanks and hot & cold pipework water systems, as part of regular operations against Legionella or after a period of inactivity or shut down. Disinfection procedures must be carried out according to protocol in the context of the correct risk assessments being completed and specific requirements considered, by those competent to do so.

Recommended Dosage Overview

Tank size (m3)

Concentration (ppm)

Minimum residence time (hours)

Quantity required (litres)

Option 1: 1 hour





Option 2: 3 hours





Training and Support

We provide comprehensive training and support in the application and use of Geosil50 – this is to help you stay compliant with the Legionella Control Association.

Qualified Service Providers need to demonstrate procedures for:

  • Formal Training Of All Staff Involved With Legionella Control
  • A System For Assessing The Competence Of Staff
  • Staff Training Needs
  • Ensure Staff Training Is Up To Date

Anyone involved in managing Legionella risk must be competent, trained and aware of their responsibilities.

Areas covered in the Geosil50 training course

  • Introduction
  • What Is Geosil50?
  • Legionella Overview
  • Where, When And How To Use It
  • Legal Framework & LCA
  • Geosil50 Method Statement
  • Responsibilities
  • Reporting – Updating Site Records
  • Service Delivery & Reporting
  • Q & A
  • LCA Cleaning & Disinfection Standards
  • Optional Checks & Tests

CPD certificates are issued to all participants on successful completion, and competency checks & tests can also be provided.

Stay Legionella Control Association compliant!

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