Understanding the New NHS Guidance on POU Water Filtration in Healthcare

The guidance offers comprehensive new requirements for the design and management of healthcare water systems, with particular emphasis on the selection, specification, and deployment of point-of-use (POU) filters. It introduces:

• Specific criteria for selecting filters,
• Expanded advice on when to use them, and
• A risk-stratified approach to water safety based on patient vulnerability.

This article outlines the key updates and what they mean for Water Safety Groups (WSGs), estates teams, and infection prevention and control (IPC) professionals.

New Guidance on Specifying Suitable POU Filters

Section 3.73 of the NETB sets out clear criteria for what constitutes a “suitable and sufficient” POU filter. Filters should now be verified to retain nontuberculous mycobacteria (NTM) and other waterborne pathogens over their claimed life cycle. Specifically, filters must:

• Use 0.2 µm absolute sterilising-grade membranes (validated to ASTM F838),
• Demonstrate efficacy under real-world healthcare conditions, including variable temperatures, intermittent usage, and daily flow volumes,
• Withstand chemical and thermal disinfection where applicable,
• Be compatible with the specific biocides and water chemistry of the facility.

The document also highlights the importance of manufacturing robustness, recommending:

• Leak integrity testing,
• Mechanical burst testing,
• Quality assurance for every unit,
• Strict protocols against refitting previously used filters.

Critically, the POU filters must be part of a documented Project Water Safety Plan (PWSP) and monitored as part of an assurance process. Training is mandated for staff responsible for installation, maintenance, and use, and filters should never be reinstalled once removed.

The takeaway for procurement teams is clear:

Selection must go beyond price and brand. Validation data, life cycle performance, and real-world compatibility are now essential procurement criteria.

When to Use Filters:
From Reactive Measure to Standard Precaution

One of the most transformative aspects of NETB 2024/03 is its endorsement of filters as a standard precautionary control, not just a reactive measure.

Where previously filters might have been reserved for use following adverse sample results or in outbreak scenarios, the updated guidance supports routine, proactive deployment in high-risk areas – especially in augmented care units, including haematology/oncology, transplant, and cystic fibrosis wards.

This signals a marked change in strategic thinking. POU filters should now be considered:

• Standard components of design in new builds and refurbishments,
• Risk mitigation tools for known high-risk populations,
• Contingency controls during commissioning, remediation, or ongoing investigations.

The guidance also encourages using POU filtration throughout the patient’s clinical pathway, with flexibility to adjust as their risk status changes during treatment or recovery.

Who Needs Protection:
Defining At-Risk Patient Groups and Escalating Water Controls

Appendix 3 of the NETB introduces a tiered framework for identifying and protecting immunocompromised patients, using four protection levels. These range from Level I (mild immunosuppression) to Level IV (extreme immunosuppression, such as during allogenic stem cell transplantation pre-engraftment).

The escalation of water control measures based on patient susceptibility introduces a more personalised approach to infection prevention.

Importantly, the guidance acknowledges that even compliant mains water may not be suitable for certain patients, due to the presence of opportunistic pathogens like Pseudomonas aeruginosa, Legionella, and NTM.

Conclusion:
A Shift Toward Risk-Based, Patient-Centred Water Safety

NETB 2024/03 represents a critical evolution in how healthcare providers manage waterborne infection risks. It:

• Moves POU filters from reactive contingency to proactive standard control,
• Demands higher technical validation and compatibility from manufacturers,
• Elevates the role of WSGs and IPC teams in the design, selection, and monitoring of water safety interventions,
• And recognises that patient susceptibility must dictate environmental controls, not just compliance with baseline water safety regulations.

As NHS Trusts prepare to align with this bulletin, the emphasis will be on embedding POU filtration into long-term water safety planning, especially for new builds and refurbishments, but also in existing infrastructure where the risk profile justifies it. By taking a precautionary, standards-led and risk-stratified approach, NHS organisations can ensure that the environments we build and operate today are safer for the most vulnerable patients tomorrow.