Spring Water Hygiene: Why March Is the Most Important Month for Your Building's Water System
As the clocks change and temperatures begin to climb, most facility managers are focused on HVAC checks, grounds maintenance, and seasonal building readiness. But there's a quieter risk that increases every spring — and it starts inside your water system.
Spring is when water systems across the UK quietly begin to fail. Not because something breaks, but because conditions shift. Warmer ambient temperatures, fluctuating building occupancy after the Easter holidays, and low-use outlets create the perfect environment for bacterial growth — particularly Legionella pneumophila, the bacterium responsible for Legionnaires' disease.
The Spring Risk Window: What Changes and Why It Matters
Legionella bacteria thrive in water temperatures between 20°C and 45°C. During winter, cold water systems typically remain below this range. But as ambient temperatures rise through March and April, stored cold water can creep into that danger zone — especially in uninsulated tanks, poorly circulated systems, or buildings with intermittent use.
This is compounded by changes in occupancy patterns. Schools reopen after half-term and Easter breaks with outlets that may not have been flushed. Office buildings operating hybrid working models see entire floors go unused for days at a time. Leisure centres ramp up and down with seasonal demand. Healthcare estates juggle variable ward occupancy across sprawling pipework networks.
The result is stagnation. And stagnation is the single biggest controllable risk factor in water hygiene compliance.
Your Spring Water Hygiene Checklist
If an inspection happened tomorrow, would your system pass? That's the question every duty holder should be asking right now. Here are the five areas that matter most heading into the warmer months.
1 Sentinel Temperature Monitoring
Are your temperature logs consistent and up to date? Cold water should be stored and distributed below 20°C, and hot water should be stored at 60°C or above, reaching outlets at no less than 50°C. As external temperatures rise, cold water temperatures are the first indicator of system vulnerability. Review your sentinel points now and confirm that monitoring frequency meets your risk assessment requirements.
2 Flushing Programme Compliance
Your quietest tap may be your biggest liability. Low-use outlets allow water to sit in pipework, creating conditions for bacterial colonisation. A flushing programme isn't a box-ticking exercise — it's a documented defence.
If something goes wrong, the first question from an inspector won't be "Did you intend to flush?" It will be "Can you prove you did?" Ensure your programme is logged, monitored, and includes every rarely used outlet in the building.
3 Tank Condition and Cleaning
Out of sight does not mean low risk. Water storage tanks are rarely inspected until a sample fails, a complaint is raised, or an audit is booked. By that point, remediation is reactive and costly.
Sediment accumulates slowly, biofilm forms quietly, and corrosion develops over time. If your tank hasn't been cleaned within the last 12 months, you're relying on assumption rather than evidence. Annual tank cleaning isn't about appearance — it's about documented compliance and measurable risk reduction.
4 Sampling Schedule
Confirm your microbiological sampling schedule is current and aligned with your risk assessment. Spring is the ideal time to carry out routine sampling before the higher-risk summer period. Proactive sampling gives you a baseline. Reactive sampling, carried out only after a problem has been identified, gives you a liability.
5 Deadlegs and Stagnation Risks
Have there been any modifications to your building's pipework? Deadlegs — sections of pipe that no longer serve an active outlet — are a common but overlooked risk. They trap water, resist treatment, and harbour bacteria.
A spring review should include a physical walk-through to identify any changes to the system that may have introduced new stagnation points.
Which Buildings Are Most at Risk?
While every building with a water system has a duty of compliance, certain property types face elevated risk during the spring transition. These include schools and universities returning from holiday closures, office buildings with hybrid occupancy patterns, healthcare facilities with complex pipework, leisure centres with seasonal demand fluctuations, and older buildings with uninsulated storage tanks or extensive deadleg networks.