T-Safe In Focus

New NHS Guidance: Reassessing POU filter specification and selection criteria

In August 2024, NHS England published Estates Technical Bulletin No. 2024/3, a pivotal update supplementing HTM: 04-01 to address the risk of waterborne pathogens, particularly in high-risk patient care areas. This bulletin transforms what were previously considered best practices into enforceable standards. Section 3.73 outlines specific, mandatory requirements for specifying and selecting point-of-use (POU) filters at taps and showers used in augmented care and immunocompromised environments.

For Water Safety Groups (WSGs), this guidance mandates full compliance. Filters must meet all listed performance, safety, and quality benchmarks. This insights article outlines the key requirements, why they matter, and the patient safety implications of non-compliance.

NETB 2024/3: Summary of Minimum POU Filter Requirements

The following criteria must now be treated as mandatory for POU filters used in high-risk healthcare settings:

Validated 0.2 µm Sterilising-Grade Filtration for Full Service Life

Filters must demonstrate full retention of pathogens (including NTM, Legionella, and Pseudomonas aeruginosa) throughout their entire claimed life under realistic healthcare conditions (intermittent flow, pressure variations, temperature range, and throughput).

Why it matters: Only filters with absolute 0.2 µm membranes and total retention can ensure against early microbial breakthrough. Point-in-time testing, without full life cycle testing, partial retention, or “log reduction”, claims are insufficient where patient vulnerability is critical.

Proven Manufacturing Robustness and Integrity Testing

Each filter unit must pass an air-pressure integrity test to confirm leak-free performance. In addition, the filter housing must be strength-tested (burst test) to ensure durability.

Why it matters: A single flaw, such as a pinhole in the membrane or a crack in the housing, can allow pathogen breakthrough. These tests ensure that each unit performs as an actual barrier, not just under ideal laboratory conditions, but also in service.

Leak-Free Secure Fitting and No Splashback

Outlets must allow filters to attach securely with no leakage and enough clearance to prevent splashback from the drain contaminating the outlet.

Why it matters: If water bypasses the filter or if dirty water splashes back onto it from the sink, the filtered stream can be re-contaminated. Ensuring compatibility between taps and filters prevents this.

Performance in Real Water Conditions

WSGs must consider the effects of poor water quality, scale, or particulates that could block filters early. Manufacturers should provide performance data under adverse conditions.

Why it matters: Unexpected filter blockages can disrupt the water supply or prompt staff to remove filters prematurely. Understanding and planning for the impact on water quality impact protects both usability and patient safety.

Biocide Compatibility

All materials in the filter (membrane, housing, seals) must be chemically compatible with disinfection regimens, including shock and continuous biocide dosing.

Why it matters: Materials that degrade in the presence of chlorine dioxide, silver peroxide, or heat can crack, leak, or leach chemicals, undermining safety and compliance.

No Reuse Once Removed

Once a filter is removed, it must not be reinstalled.

Why it matters: Reattaching a used filter can release trapped pathogens or expose the filter to contaminated source water or environmental reservoirs, resulting in retrograde contamination. Even a brief removal invalidates the sterility of the patient-side water path.

Cleaning Protocols in Place

Hospitals must define who is responsible for cleaning the external surfaces of outlets and filters, and the method of completing this task.

Why it matters: Biofilm and contamination can build up externally. Regular cleaning prevents contamination at the filter outlet and ensures filtered water remains safe up to the point of contact.

Regulatory Compliance and User Training

Filters must comply with the UK Water Supply (Water Fittings) Regulations. Staff involved in the installation, use, and disposal must be adequately trained.

Why it matters: Incorrect installation, use of non-compliant fittings, or improper handling can introduce new risks, even with a high-quality filter.

Documentation and Traceability

Hospitals must log filter installations, changes, failures (e.g., leaks, blockages), and other anomalies.

Why it matters: Traceability ensures timely replacement, enables root cause analysis of failures, and demonstrates compliance with audit trails.

Defined Use and Removal Criteria

Clear protocols are necessary to determine when filters should be fitted and safely removed; this must be included in the Water Safety Plan.

Why it matters: Without predefined criteria, filters may be overused or removed too early, exposing patients to risk.

Blocked Filter Investigation Pathway

An investigation protocol must be in place to understand and resolve any early filter blockages, with support from the manufacturer.

Why it matters: Premature blockages can signal water quality issues or filter limitations. Investigating helps prevent recurrence and improves future safety.

Scrutinising Suppliers: Questions to Ask

To ensure NETB compliance, Estates and IPC professionals should demand evidence of:

Bacterial retention data for the full claimed life (including ASTM F838 testing)
Quality assurance protocols including integrity and burst testing
Biocide resistance documentation
Material compliance (WRAS, EU food contact)
Training materials and SOPs
Response plans for early blockages or complaints

Filters lacking this evidence should not be considered suitable for patient protection in high-risk settings.

Compliant vs. Non-Compliant Filters: What’s the Difference?

Compliant filters are medical grade, validated, and supported by technical documentation. They may cost more but are designed for high-risk environments.
Non-compliant filters often:

Use nominal filtration (not absolute)
Skip integrity testing
Offer weak or no support for NHS-grade installation and maintenance
Degrade in biocides or heat
Lack proper documentation or training

Relying on non-compliant products risks harm, non-compliance with NETB 2024/03, and potential liability.

Conclusion

The new POU filter requirements outlined in NETB 2024/3 set a clear and enforceable standard for protecting immunocompromised patients. No longer can filters be selected based on cost or convenience alone. WSGs and IPC teams must critically assess whether their current suppliers meet all criteria, backed by hard evidence. Every filter in a high-risk patient area must act as a certified, validated, and documented microbial barrier from day one to day thirty-one (or longer), without exception.

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