Does my Phoenix building need a Legionella water plan?

The CDC's worksheet has four questions for whole buildings and four for devices. The worksheet is built to "quickly assess the need for a water management program," and a "yes" points toward one. The building questions are:

1. 1Is it a healthcare facility where patients stay overnight, or does it house or treat people who have chronic and acute medical problems or weakened immune systems? The CDC's footnote lists "burns, cancer, solid organ or bone marrow transplant, kidney disease, diabetes, or chronic lung disease."
2. 2Does it "primarily house people older than 65 years," like a retirement home or assisted-living facility?
3. 3Does it have "multiple housing units and a centralized hot water system (like a hotel or high-rise apartment complex)"?
4. 4Does it have "more than 10 stories (including basement levels)"?

The device questions apply even when the building itself does not qualify. The CDC says "devices in buildings that can spread water droplets containing Legionella should have a WMP even if the building itself does not." Those devices are a cooling tower, a hot tub that is not drained between each use, a decorative fountain, and a centrally installed mister, atomizer, air washer or humidifier.

### Who is left out

The CDC says the building standards in its toolkit "don't apply to" single-family residences or small multiple-family residences such as duplexes. That holds "even if they include" the devices above. The CDC still tells residents to take steps against waterborne disease. By the worksheet's questions, a typical Phoenix office, shop or restaurant does not qualify unless it has one of those devices, a very tall building or a group of residents at higher risk. That does not make hot water maintenance optional. It only means the CDC's worksheet does not call for a formal program.

The CDC's overview lists seven steps:

1. 1Establish a WMP team
2. 2Describe the building water systems
3. 3Identify areas where Legionella could grow and spread
4. 4Decide where to apply and how to monitor control measures
5. 5Establish interventions when control limits are not met
6. 6Ensure the program runs as designed and is effective
7. 7Document and communicate all the activities

The CDC says "each program has to be tailored for each particular building at a particular point in time," and that "a consultant with Legionella-specific environmental expertise may sometimes be helpful." A plumber is one member of that team. The plumber's job is the physical system: pipes, heaters, valves and fixtures. Writing and running the program is a separate job.

The CDC's potable water module says "sediment and biofilm, temperature, water age, and disinfectant residual are the key factors that affect Legionella growth." Most of its plumbing recommendations fall into those groups.

### Temperature

The CDC gives these control limits:

• Hot water storage: "Store hot water at temperatures above 140°F (60°C)."
• Circulating hot water: "Ensure hot water in circulation does not fall below 120°F (49°C). Recirculate hot water continuously, if possible."
• Cold water: Keep it below the range Legionella favors, which the CDC gives as 77 to 113 degrees F, and it notes that Legionella "may grow at temperatures as low as 68°F (20°C)."

Maricopa County's guide for food businesses says much the same. It says "maintaining water heater systems at 140°F or higher and providing water to faucets at a minimum of 122°F will reduce the growth and likelihood of Legionella." It also warns that large systems with "tepid zones, scale and sediment accumulations, 'dead leg' sections of plumbing, non-recirculation plumbing lines, and temperatures maintained below 140°F" create the ideal environment for growth. Its plan review minimum for a heater set-point is lower, at 120 degrees F, so the higher number is advice for people managing risk. Our page on the water temperatures required in a commercial kitchen covers the county's minimums.

Hotter storage raises the scald risk at the tap. The CDC's answer is to "install thermostatic mixing valves as close as possible to fixtures," which prevents scalding "while permitting circulating hot water temperatures above 120°F."

### Water age and dead legs

The CDC says to "eliminate dead legs, which are sections of no- or low-water flow," and to "flush low-flow piping runs and dead legs at least weekly." It adds that infrequently used fixtures such as eye wash stations and emergency showers should be flushed regularly. This is where a vacant suite, a closed wing or a seasonal restroom becomes a risk. The CDC also says to "flush after an intrusion event (e.g., water main break)."

Long unused runs are a plumber's finding. Our page on the 45 second hot water rule explains how a recirculation loop shortens the wait for hot water, and whether a recirculation pump is worth it explains how they work.

### Sediment and scale

The CDC says to clean and maintain "water heaters, mixing valves, aerators, showerheads, hoses, and filters" regularly. Flushing a tank removes sediment. Our page on how often to flush a water heater in Phoenix covers the residential schedule, and the county guide covers commercial servicing.

### Other parts of the system

Two more CDC points affect plumbing choices:

• Insulate the pipe "to maintain hot- and cold-water temperatures throughout the water system."
• Watch what speeds up disinfectant decay. The CDC says to identify components "that speed the decay of disinfectant residuals," and lists "UV devices, water softeners, carbon filters, and heaters." That is worth knowing before adding treatment equipment.

The CDC also says "thermal shock of water systems isn't recommended due to frequent failure and rapid recolonization of Legionella." Heating the system to a high temperature for a short time is not a lasting fix. The CDC says "following a successful remediation procedure, Legionella will likely recolonize the water system if the underlying conditions supporting growth aren't addressed."

Start small and write things down.

1. 1Answer the CDC's eight questions for your building. If any answer is yes, treat a WMP as expected.
2. 2Ask who requires it. Check your license, your insurer and your lender, since the requirement may come from them.
3. 3Draw the hot water system. Mark the heater, the loop, every dead end and every rarely used fixture.
4. 4Measure temperatures at the heater, at the far end of the loop and at a few fixtures.
5. 5Get a plumber's look at dead legs, mixing valves, scale and heater settings.
6. 6Consider a consultant. The CDC says one may help with the program itself.

HQ Plumbing & Air is licensed and insured, and can inspect the hot water system for dead legs, heater settings, mixing valves and scale, and report what we find. We offer free estimates and upfront pricing. A plumber's inspection does not replace the written program or a doctor's advice.

Mixing valves are part of how buildings store water hot and still deliver it safely, as covered in what a thermostatic mixing valve is and why commercial buildings use one.