ASHRAE 188 control limits, monitored at every control point
ASHRAE Standard 188 sets how building owners manage Legionella risk in water systems through a water management program. The program sets control limits, monitors them and records corrective action. Aqueduct monitors temperature and flow at control points and keeps each excursion with its fix.
Who it applies to
ASHRAE 188, Legionellosis: Risk Management for Building Water Systems, covers human-occupied commercial, institutional, multiunit residential and industrial buildings, but not single-family homes. The current edition is 188-2021. It is a consensus standard, voluntary unless a jurisdiction or contract adopts it; ASHRAE Guideline 12-2023 gives the practical detail.
For US healthcare it is effectively required. Since CMS memo QSO-17-30, hospitals, critical access hospitals and long-term care facilities must have a water management plan, and surveyors check it.
What a water management program needs
Terms as defined in ASHRAE 188 and CMS QSO-17-30. Your program team owns the plan and its limits.
| Requirement | What it asks for | Data Aqueduct supplies |
|---|---|---|
| Building survey (Section 5) | A documented survey deciding whether the building needs a program. | An asset model of tanks, heaters, risers and outlets per building. |
| Process flow diagram | A diagram of how water moves through the building. | The water network in aQ Core, from incoming supply to outlets. |
| Control limits | A maximum, minimum or range for each monitored parameter, such as temperature. | Each reading compared with the range for its point. |
| Monitoring | Planned measurements showing control measures work. | Continuous temperature and flow at heaters, returns and remote outlets. |
| Corrective action | Steps that bring values back within limits, documented. | Each excursion kept with its alert, work order and closing reading. |
| CMS testing protocols | Provider-defined tests for each control measure, with results and actions documented. | Exports by control point and period for the survey. |
Numbers that matter
Pressure below which ASHRAE 188 treats a supply as a water service disruption, a trigger for review.
Source: ASHRAE 188-2018, public copyCMS memo QSO-17-30 made water management plans an expectation for hospitals and long-term care, revised in 2018.
Source: CMSRelated standards
sites in 21 countries run on Aqueduct.
and 9 clinics in one of India’s top hospital chains.
US airport running water intelligence on Aqueduct.
of commercial real estate under Aqueduct.
FMCG manufacturing campus.
operations run on Aqueduct.
Related
Common questions
No. CMS states that it does not require water cultures for Legionella. The provider's program decides what to test and how often, and Aqueduct supplies the continuous temperature and flow readings that show control measures working between tests.
ASHRAE 188 leaves frequency to the program team. Continuous sensors settle the question for temperature and flow, and they show stagnation that a weekly round misses. Aqueduct raises an alert the hour a point leaves range, not at the next round.
The CDC publishes a free toolkit that walks a team through building a program in seven steps, ending with documenting and communicating the work. It sits alongside ASHRAE 188, and Aqueduct supplies the monitoring record the later steps rely on.
Aqueduct reads cooling tower make-up, blowdown, temperature and run status where metered, and flags stagnant or idle periods that a program team treats as risk conditions. Water treatment and disinfectant dosing stay with your treatment contractor, whose readings can be imported. See digital twin.
See Aqueduct on your own facility.
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