Assessing Drinking Water in Healthy Buildings: 7 Tips

TIPS: Healthy Buildings Drinking Water Assessment

7 Tips for Assessing Drinking Water Quality in Healthy Buildings

Building water systems pose health risks that go beyond what standard plumbing codes address. Legionella, lead, copper, and disinfection byproducts can accumulate in building water systems even when the municipal supply meets all regulatory standards. These seven tips guide building operators, facilities managers, and healthy buildings practitioners through a practical drinking water assessment framework.

6,000+

Legionellosis Cases Annually

CDC reports over 6,000 cases of Legionnaires disease annually in the US, with the majority traced to building water systems including cooling towers, hot tubs, and large plumbing networks.

Source: CDC | Legionellosis Surveillance

15 ppb

EPA Lead Action Level

The EPA Lead and Copper Rule action level is 15 parts per billion at the tap. Building plumbing components are the primary source of lead in water that meets all treatment standards at the plant.

Source: EPA | Lead and Copper Rule

60C

Legionella Kill Temperature

Maintaining hot water at or above 60 degrees C at the heater and 51 degrees C at all outlets is the primary thermal control strategy for Legionella in building water systems under ASHRAE 188.

Source: ASHRAE | ASHRAE Standard 188

Tip 1: Start with a Building Water System Inventory

Before any water quality assessment can be meaningful, you need a complete inventory of every water system component in the building. This includes all hot and cold water distribution lines, storage tanks, water heaters, cooling towers, decorative fountains, ice machines, eye wash stations, hose bibs, and any water-using equipment that may generate aerosols. Legionella and other waterborne pathogens colonize specific system components, and you cannot assess risk you have not documented.

The inventory should map water flow paths from the municipal connection to every point of use, identify dead legs (pipe sections where water sits stagnant), low-use outlets, and components where water temperature falls into the Legionella growth range of 25 to 45 degrees C. This inventory becomes the foundation of the Water Management Plan required under ASHRAE Standard 188.

Tip 2: Develop and Implement a Water Management Plan

ASHRAE Standard 188 requires buildings above defined thresholds to develop a Water Management Plan (WMP) that identifies hazardous conditions, establishes control measures, sets monitoring and testing frequencies, and defines corrective actions when limits are exceeded. A WMP is not a one-time document: it is an operational program with assigned responsibilities, defined limits, and documented results.

WMP Element

What It Requires

System description and flow diagram

A schematic describing every water system component and how water flows through the building, identifying potential Legionella amplification sites.

Hazard analysis and control measures

Identification of conditions that could lead to Legionella growth (stagnation, temperature in growth range, scale, biofilm) and the specific control measures applied to each hazard.

Monitoring and testing schedule

Defined frequencies for temperature monitoring, disinfectant residual testing, and Legionella culture testing at specified system locations reflecting the risk profile of each component.

Corrective action procedures

Predefined responses when control limits are exceeded, including immediate actions (flushing, superheating, hyperchlorination) and follow-up testing to confirm effectiveness.

Source: ASHRAE | ASHRAE Standard 188 Legionellosis Risk Management

Tip 3: Monitor Water Temperatures Throughout the System

Temperature is the most practical and continuously controllable Legionella prevention measure. Hot water must be stored at or above 60 degrees C and delivered to all outlets at or above 51 degrees C. Cold water must be maintained below 20 degrees C throughout distribution. Temperatures between 25 and 45 degrees C represent the Legionella growth zone and must be avoided wherever water is stored or moves slowly.

Temperature monitoring must cover the full distribution system, not just the heater outlet. Long hot water runs, distant fixtures, recirculation loop returns, and sentinel taps should all be included in a representative monitoring program. A heater set to 60 degrees C that delivers 38-degree water at a distant tap due to heat loss along an uninsulated pipe represents a compliance gap that the heater thermostat reading alone will not reveal.

Tip 4: Implement a Flushing Program for Low-Use Outlets

Stagnant water in low-use outlets, dead-end pipe sections, and infrequently used fixtures is one of the primary conditions that enables Legionella colonization and lead release. Buildings with vacant floors, seasonal closures, or newly reoccupied spaces after periods of low use face elevated risk. A systematic flushing program addresses stagnation at the point of use.

Flushing Priorities by Outlet Type

High Priority

Kitchen taps, drinking fountains, ice machines, eye wash stations, showers used by vulnerable occupants

Medium Priority

Restroom sinks and toilets in areas with intermittent occupancy, hose bibs, utility sinks not used daily

After Extended Vacancy

Full system flush before reoccupancy, starting at the meter and working to all points of use; confirm disinfectant residual and temperature before clearance

Documentation

Log date, time, outlet, duration, and pre/post temperature or residual for each flushing event

Tip 5: Test for Lead at the Tap

Lead in building drinking water comes from lead service lines, lead solder in older plumbing, brass fittings, and lead-lined tanks, not from the municipal treatment plant. Buildings constructed before 1986 are at highest risk. Schools, childcare facilities, and healthcare buildings face heightened obligations given the vulnerability of their occupants to lead neurotoxicity.

First-draw sampling identifies lead from the immediate fixture and nearby plumbing. Sequential sampling identifies where in the plumbing system lead is entering the water. Both methods are needed for a complete lead assessment. Results above 1 ppb in schools and childcare facilities, or 15 ppb at any tap, require immediate remediation including fixture replacement and communication to building occupants.

Tip 6: Verify Disinfectant Residuals at Points of Use

Municipal water suppliers maintain disinfectant residuals to prevent microbial contamination during distribution. However, residuals dissipate as water travels through building plumbing, particularly in long runs, low-use areas, and sections with high organic load from biofilm or scale. Testing disinfectant residuals at points of use, not just at the building entry, reveals where protection has been lost.

Free chlorine residuals below 0.2 mg/L or total chlorine residuals below 0.5 mg/L at points of use indicate inadequate protection and increased Legionella risk. Buildings that rely on supplemental disinfection systems must verify that these systems are performing as designed at all protected outlets.

Tip 7: Manage Cooling Towers and Decorative Water Features Separately

Cooling towers and decorative water features are among the highest-risk Legionella amplification sites in buildings because they generate aerosols that can transmit Legionella directly to nearby occupants and to the building’s air intake system. They require separate management programs from the domestic water system, with their own monitoring and corrective action procedures within the building’s Water Management Plan.

Cooling tower management must include regular physical cleaning and disinfection, biocide treatment programs with documented efficacy, drift eliminators to reduce aerosol generation, and shutdown and startup procedures that prevent Legionella from proliferating during periods of inactivity. Decorative features that cannot be maintained at protective temperatures must use appropriate biocide treatment and regular drain-down and cleaning schedules.

Key Takeaways

A WMP Is the Foundation

Every tip in this list is a component of a Water Management Plan. Buildings above ASHRAE 188 thresholds need a documented, operational WMP that assigns responsibilities, sets limits, and creates the record that demonstrates proactive management.

Test at the Tap, Not Just the Entry

Municipal water quality at the building entry tells you almost nothing about what occupants drink at the tap. Lead, Legionella, and disinfectant residual problems are building-specific. Testing must occur at representative points of use throughout the distribution system.

Stagnation Is the Enemy

Low-use outlets, dead legs, and building vacancy create conditions that enable both Legionella growth and lead release. Flushing programs and dead-leg elimination are among the most cost-effective water quality interventions available to building operators.

Government and Regulatory Sources

Related VelSafe Articles

Start with the Water System You Can See

Building water quality assessment begins with documentation of every system component, followed by systematic testing at the tap. The gap between municipal supply compliance and actual occupant exposure at the fixture is where Legionella outbreaks, lead poisoning cases, and building-related illness clusters originate. Operators who implement a Water Management Plan, maintain temperature control, flush low-use outlets, and test at representative points of use close that gap systematically rather than reactively. Find more healthy buildings water quality resources at velsafe.com.