Commercial Cooling Tower Blowdown & Conductivity Controller Drift: Cycles of Concentration, Toroidal Sensor Fouling, Chiller Condenser Tube Scaling & ASSE 1013 Biocide Backflow Containment

At 1:15 PM on a ninety-eight-degree Wednesday afternoon in the middle of a July heatwave in Broomfield, Colorado, the central chiller plant inside a six-story corporate financial headquarters in Interlocken suffers a catastrophic high-head shutdown.

The building automation system (BAS) flashes a red critical alarm: CHILLER #1 REFRIGERANT HIGH PRESSURE TRIP — CONDENSER WATER TEMPERATURE 104°F.

Inside the building, chilled air ceases circulating. Executive suites, conference halls, and server rooms begin rapidly heating up.

Up on the commercial roof deck, the lead facility engineer walks over to the twin 400-ton induced-draft cooling towers.

The sight and sound are deeply alarming.

The cooling tower basin is violently overflowing. Warm water is pouring over the fiberglass perimeter louvers, cascading across the commercial roof membrane, and ponding two inches deep around the mechanical penthouse doors.

Meanwhile, inside the digital chemical water treatment enclosure, the automated conductivity controller displays a serene reading: **950 microSiemens per centimeter ($\mu\text{S/cm}$)**.

According to the controller screen, the water is perfectly clean.

The engineer pulls out a calibrated handheld digital conductivity meter and dips the probe directly into the churning cooling tower basin.

The handheld screen instantly flashes: **4,620 $\mu\text{S/cm}$**.

The automated toroidal conductivity sensor has suffered severe calibration drift.

Coated in a dense, slimy layer of biological biofilm and calcium carbonate crust, the sensor went blind. It falsely reported that the water was clean, keeping the motorized blowdown valve permanently shut for over three weeks.

Because water constantly evaporated under the blazing Colorado sun while dissolved minerals were trapped inside, the cooling tower’s mineral concentration exploded to over nine cycles of concentration.

Dissolved calcium carbonate, silica, and sulfates reached severe supersaturation.

They precipitated out of solution, coating the copper-nickel condenser tubes inside the chiller heat exchanger with a rock-hard layer of insulating mineral scale.

Even worse, because the blowdown valve failed to operate while the makeup water valve jammed open under scale accumulation, toxic chemical biocides—including glutaraldehyde and isothiazolinone—are washing over the roof and threatening to siphon backward into the building’s domestic drinking water system.

Commercial cooling tower blowdown and chemical treatment failures are high-consequence mechanical and environmental emergencies. When conductivity controllers drift or blowdown valves fail, thousands of dollars in water treatment chemicals are lost, chillers suffer irreversible thermodynamic damage, and severe biological hazards—including *Legionella pneumophila* outbreaks—threaten public health.

Let’s explore the fluid thermodynamics, mass balance equations, water chemistry, sensor physics, and master plumber cross-connection control protocols governing commercial cooling towers across the Colorado Front Range.

1. The Thermodynamics & Mass Balance of Evaporative Cooling Towers

Commercial water-cooled chiller plants rely on evaporative cooling towers to reject heat extracted from the building into the outdoor atmosphere.

The cooling tower functions through a fundamental physical principle: **The Latent Heat of Evaporation**.

For every single pound of water that evaporates from liquid to water vapor, approximately **1,000 BTUs of thermal energy** are absorbed and removed from the recirculating condenser water loop:

$$h_{fg} \approx 1,000\text{ BTU/lb of water evaporated}$$

Warm condenser water leaving the chiller heat exchanger at 95°F is pumped to the top of the tower, sprayed through distribution nozzles over polyvinyl chloride (PVC) film fill, and exposed to high-velocity airflow drawn by giant induced-draft fans.

As water cascades down through the fill pack, roughly 1% to 2% of the water evaporates into the passing air stream, cooling the remaining 98% down to 85°F before it collects in the cold water basin and returns to the chiller.

The Conservation of Mass & Dissolved Solids

Here is the thermodynamic catch: **Only pure, distilled $\text{H}_2\text{O}$ molecules evaporate into the air.**

Every grain of dissolved mineral hardness (calcium, magnesium, silica, chlorides, and sulfates) present in the city makeup water remains trapped behind in the cooling tower basin.

The overall hydraulic mass balance equation for a cooling tower is:

$$M = E + B + D$$

Where:

• $M$ = Makeup water volume added to the tower (gallons per minute, GPM).
• $E$ = Evaporation loss rate (GPM). Typically calculated as $E = 0.0008 \times \text{GPM}_{circulating} \times \Delta T_{range}$.
• $B$ = Blowdown (bleed-off) rate intentionally discharged to the sanitary sewer (GPM).
• $D$ = Drift loss (water droplets physically entrained in the discharge air, typically $< 0.005\%$ with modern drift eliminators).

As pure water constantly evaporates, dissolved solids become increasingly concentrated.

To keep minerals from precipitating into solid rock, a portion of the mineral-laden basin water must be continuously or periodically drained to the sewer—this is **Blowdown ($B$)**—and replaced with fresh municipal water.

2. Cycles of Concentration ($C$) & The Chemistry of Mineral Scaling

Plumbing engineers and water treatment specialists quantify mineral concentration using **Cycles of Concentration ($C$ or $CoC$)**.

Cycles of Concentration represent the ratio of dissolved solids in the recirculating tower water compared to the fresh incoming city makeup water:

$$C = \frac{\text{TDS}_{tower}}{\text{TDS}_{makeup}} = \frac{[\text{Cl}^-]_{tower}}{[\text{Cl}^-]_{makeup}} = \frac{\text{Conductivity}_{tower}}{\text{Conductivity}_{makeup}}$$

Where $\text{TDS}$ is Total Dissolved Solids in parts per million (PPM) and conductivity is measured in microSiemens per centimeter ($\mu\text{S/cm}$).

Rearranging the steady-state mass balance equations yields the required blowdown flow rate ($B$):

$$B = \frac{E}{C – 1} – D$$

Because drift ($D$) is negligible in modern commercial towers, the formula simplifies to:

$$B = \frac{E}{C – 1}$$

The Delicate Operational Window: Water Conservation vs. Scale Destruction

Look closely at that mathematical relationship. It dictates the entire operating economics of a commercial facility:

The Langelier Saturation Index (LSI) & Heat Transfer Penalty

When mineral cycles climb above 7.0, the water’s **Langelier Saturation Index (LSI)** swings deeply positive ($LSI > +2.0$).

At this point, calcium carbonate can no longer remain dissolved in water.

It precipitates out at the hottest surface in the entire loop: **The copper-nickel tubes inside the chiller condenser bundle**.

Calcium carbonate has a thermal conductivity ($\kappa$) of roughly **0.8 to 1.3 BTU/hr$\cdot$ft$\cdot$°F**—compared to **223 BTU/hr$\cdot$ft$\cdot$°F** for clean copper!

A microscopic mineral scale layer measuring just **0.012 inches (12 mils / 0.3 mm)** thick acts as an impenetrable thermal insulator.

It reduces chiller heat transfer efficiency by **22 to 30 percent**, driving compressor electrical draw through the roof and triggering high-refrigerant-pressure safety shutdowns.

3. Forensic Pathology: Why Conductivity Controllers Drift & Solenoids Fail

How does a modern, micro-processor-controlled cooling tower water treatment system allow mineral cycles to spiral out of control?

The mechanical breakdown traces back to two critical components: **The Conductivity Sensor** and **The Automated Blowdown Valve**.

Failure Mode 1: Toroidal vs. Contacting Sensor Drift & Slime Fouling

Cooling tower automation systems monitor total dissolved solids indirectly by measuring electrical conductivity in microSiemens per centimeter ($\mu\text{S/cm}$).

Two primary sensor technologies are deployed:

1. Contacting Conductivity Sensors: Utilize two or four metal electrodes (typically 316 stainless steel, titanium, or graphite) in direct physical contact with the water stream. A tiny AC voltage is applied between electrodes, and the resulting current is measured.
2. Toroidal (Electrodeless / Inductive) Sensors: Utilize two encapsulated wire-wound magnetic coils encased in a chemical-resistant plastic donut (polypropylene, PVDF, or PEEK). The primary coil induces an alternating electric current in the surrounding water, and the secondary coil detects the induced magnetic field proportional to the solution’s conductivity.

Contacting sensors are notorious for **fouling-induced calibration drift**.

In the warm, nutrient-rich environment of an open cooling tower, bacterial slime, algae, and suspended silt constantly circulate.

Biological biofilm sticks to the metal electrode surfaces.

Because biofilm has high electrical resistivity, it acts as an electrical insulator.

The sensor cannot pass current through the slime layer. It “sees” low current and calculates a falsely low conductivity.

The controller believes the water is clean ($900\text{ }\mu\text{S/cm}$), when actual water conductivity has reached $4,000\text{ }\mu\text{S/cm}$.

The controller never signals the blowdown valve to open. The tower continues concentrating minerals until the chiller trips.

While toroidal sensors have no exposed metal electrodes and resist fouling significantly better, they can still drift if heavy calcium scale deposits inside the center bore of the donut, restricting the fluid channel and distorting inductive flux lines.

Failure Mode 2: Blowdown Valve Mechanical Seizure

Even if the conductivity controller detects high mineral levels and sends a 24VAC or 120VAC signal to bleed down, the physical valve must open reliably.

Commercial blowdown systems utilize either:

• Direct-Acting or Pilot-Operated Solenoid Valves: Fast-acting brass or stainless steel valves with an internal rubber diaphragm and pilot bleed port.
• Motorized Electric Ball Valves: Quarter-turn full-port ball valves driven by an electric reversing actuator motor.

Solenoid valves are highly prone to mechanical failure in cooling water applications.

The pilot bleed orifice in a solenoid valve measures less than **0.020 inches**. A single grain of cooling tower airborne dust, rust scale, or biomass will plug this tiny orifice.

When the pilot orifice clogs:

• If clogged while closed: The valve cannot lift its diaphragm. The tower cannot blow down. Mineral concentration explodes.
• If scale chips lodge under the main seat: The valve cannot close. Water flows continuously to the sewer (20 to 50 GPM) 24 hours a day. The facility bleeds away thousands of dollars in water and expensive chemical corrosion inhibitors.

Motorized ball valves provide vastly superior reliability because their full-port bore has zero pilot orifices to clog. However, if scale accumulates on the ball seats, actuator motor gears can strip or thermal overloads can trip, freezing the valve in a static position.

4. Chemical Biocides & Life-Safety Cross-Connection Control (ASSE 1013)

A cooling tower is an open-air biological scrub chamber.

Every day, thousands of cubic feet of outdoor air pass through the wet fill. The tower scrubs dust, pollen, bird droppings, fungal spores, and bacteria out of the atmosphere.

Warm water (85°F to 105°F) combined with sunlight and organic debris creates the perfect incubation broth for deadly pathogens, primarily ***Legionella pneumophila***—the bacterial agent responsible for Legionnaires’ disease.

To prevent public health outbreaks, commercial cooling towers are continuously or intermittently dosed with chemical biocides:

The Backflow Threat: ASSE 1013 RPZ Protection Mandate

Because of these highly toxic chemical biocides, **Colorado Department of Public Health and Environment (CDPHE) Regulation 11 and IPC Section 608.16.2** classify commercial cooling towers as a **High-Hazard Cross-Connection**.

The potable water line feeding the cooling tower’s makeup valve connects the municipal public drinking water distribution system directly to a vat of water laced with glutaraldehyde and isothiazolinone.

If a sudden drop in municipal water pressure occurs—such as a street fire hydrant opening or a city main rupture—the potable supply line experiences negative pressure (back-siphonage).

If the makeup water line lacks proper backflow protection, toxic cooling tower water will be siphoned straight out of the tower basin and pulled into the building’s domestic drinking fountains, kitchen cafeteria lines, and public lavatories!

To prevent this catastrophe, plumbing codes strictly mandate one of two backflow barriers:

1. Physical Air Gap: A vertical physical air separation between the lowest point of the potable supply pipe and the flood level rim of the cooling tower basin. The air gap must measure a minimum of **twice the inside diameter of the supply pipe, and never less than 1.0 inch** (governed by ASME A112.1.2).
2. ASSE 1013 Reduced Pressure Zone (RPZ) Backflow Preventer: If the makeup line connects below the rim or directly to an automated float fill valve, a certified ASSE 1013 RPZ assembly must be installed on the supply line. An RPZ assembly provides continuous mechanical and hydraulic differential pressure protection, automatically dumping water to the drain if either check valve leaks under backpressure or back-siphonage conditions.

5. Front Range Environmental Physics: High-Altitude Evaporation & Water Sourcing

Operating commercial cooling towers in Broomfield (elevation 5,400 feet above sea level) presents distinct challenges compared to coastal installations:

1. High Evaporative Rates & Low Relative Humidity

Colorado’s Front Range is renowned for semi-arid conditions with low ambient summer relative humidity (often dropping below 15% to 20% on hot afternoons).

Because the wet-bulb temperature is significantly lower than the dry-bulb temperature, cooling towers achieve exceptional thermodynamic heat rejection.

However, the low humidity dramatically increases the **Evaporation Rate ($E$)**.

A 500-ton cooling tower in Broomfield can easily evaporate **15 to 20 gallons of water per minute** under peak afternoon sun.

Because water evaporates so rapidly, mineral cycles of concentration rise twice as fast as they would in humid Houston or Miami.

If a blowdown valve fails in Broomfield, a cooling tower can cross from a safe 4.0 cycles into severe 9.0+ cycles in less than thirty-six hours!

2. High Dissolved Silica in Front Range Waters

Water sources derived from Rocky Mountain granite and volcanic runoff contain elevated levels of dissolved reactive silica ($\text{SiO}_2$), often measuring 15 to 25 mg/L in raw municipal water.

Silica is the nightmare of industrial water treatment.

Unlike calcium carbonate—which can be dissolved and descaled using inhibited hydrochloric or sulfamic acid—precipitated amorphous silica glass is virtually impervious to standard chemical descaling acids.

If cooling tower cycles of concentration allow silica levels to exceed **150 to 180 mg/L**, silica plates out as a hard glass crust on chiller tubes.

The only way to remove silica scale is dangerous hydrofluoric acid or manual rotary tube brushing with diamond-grit flail heads.

Master plumbers in Broomfield program conductivity controllers with strict silica ceiling limits to guarantee cycles never push silica past 140 mg/L.

6. Real-World Field Case Studies Across Broomfield

Here are five forensic field case studies from our Broomfield commercial emergency master plumbing archives:

Case Study 1: Interlocken Technology Campus Chiller High-Head Trip

Facility: A 180,000-square-foot corporate software campus in Interlocken with a 500-ton water-cooled centrifugal chiller plant.

The Emergency: On an unseasonably hot June afternoon, the primary chiller tripped offline on high condenser refrigerant pressure. Building temperatures surged to 82°F, threatening sensitive server labs. The local HVAC contractor quoted an emergency $45,000 chiller compressor rebuild, claiming the motor had failed.

Investigation: Our commercial master plumbing diagnostics team arrived on site. We bypassed the compressor and inspected the cooling tower water loop.

We discovered the cooling tower’s automated blowdown motorized ball valve was frozen solid in the closed position—scale buildup on the Teflon seat had stripped the plastic drive gear inside the 24VAC actuator motor.

We tested the tower basin water with a calibrated refractometer and digital conductivity probe: conductivity was screaming at **5,400 $\mu\text{S/cm}$** (over 11 cycles of concentration!).

We opened the chiller condenser water head bells and ran a borescopic camera down the copper tubes.

Every single tube was coated with a 0.025-inch thick white calcium carbonate crust, choking heat rejection.

The Solution:

1. We set up a closed-loop chemical descaling circulation skid. We circulated inhibited sulfamic acid with dynamic pH buffering through the condenser bundle for eight hours, dissolving over 85 pounds of mineral scale without attacking the base copper.
2. We replaced the failed motorized blowdown valve with a heavy-duty industrial Belimo spring-return electric ball valve equipped with a visual position indicator.
3. We performed a complete blowdown of the cooling tower basin, cleared the distribution nozzles, and recalibrated the conductivity controller.

Outcome: Upon restarting, chiller condenser head pressure dropped by 42 PSI, approach temperatures normalized to 1.5°F, and full building cooling was restored by 8:00 PM without requiring compressor replacement.

Case Study 2: Flatiron Retail Concourse Roof Deck Basin Overflow

Facility: A high-traffic commercial retail pavilion near Flatiron Crossing Mall.

The Emergency: Water was cascading down an exterior structural wall and leaking through expansion joints into a second-floor designer retail boutique. The store manager reported thousands of dollars in ruined merchandise.

Investigation: We climbed to the roof and traced the flood to a 300-ton evaporative cooling tower.

The tower basin was overflowing continuously at approximately 35 GPM.

The previous maintenance contractor had attempted to resolve an intermittent low-water alarm by installing an oversized mechanical brass float valve.

Because the float arm was improperly adjusted, the water level sat only 1/2 inch below the basin overflow lip.

When the twin cooling tower fans cycled off on minimum cooling demand, the water suspended in the fill pack drained back down into the basin.

The surge of water overwhelmed the shallow basin headspace, pouring over the louvers onto the roof.

Even worse, the roof drain adjacent to the tower was clogged with leaves and bird nesting, creating a six-inch lake across the roof membrane.

The Solution:

1. We snaked and hydro-jetted the commercial roof drains, clearing the biological blockage and immediately relieving water ponding.
2. We removed the mechanical float valve and installed an electronic multi-probe level controller (Stilling Well float tree) that maintains water level 3.5 inches below the overflow line during active operation.
3. We re-piped the basin overflow line directly into a dedicated 3-inch indirect waste receptor with an ASME air gap, preventing roof flooding in the event of future mechanical failures.

Outcome: Basin surges are now fully contained within the basin reservoir, with zero water discharge to the roof surface.

Case Study 3: Regional Healthcare Pavilion Biocide Backflow Incident

Facility: A multi-specialty medical outpatient clinic along US-36 in Broomfield.

The Emergency: Clinic staff noticed a sharp chemical, medicinal odor and cloudy water flowing from drinking fountains on the third floor directly beneath the roof mechanical room.

Investigation: Our emergency master plumbers responded immediately. We shut down the main domestic water service and initiated water sampling.

We discovered that the 1-inch makeup line serving the rooftop cooling tower had an unapproved, uninspected dual-check backflow preventer instead of an ASSE 1013 RPZ assembly.

During an unannounced municipal water main shutdown by city crews on 120th Avenue, water pressure dropped to -5 PSIG.

The mechanical float valve on the cooling tower had jammed open with algae.

The negative pressure pulled a siphon, drawing 40 gallons of chemical-treated tower water—containing isothiazolinone biocide and phosphonate corrosion inhibitors—backward into the clinic’s domestic supply riser!

The Solution:

1. We immediately issued a mandatory DO NOT DRINK order across the facility.
2. We isolated the cooling tower line and installed a certified 1-inch ASSE 1013 Reduced Pressure Zone (RPZ) backflow preventer with an air-gap discharge drain funnel.
3. We executed an exhaustive building-wide potable water decontamination protocol: chlorinating the system at 50 PPM for four hours, followed by continuous high-velocity flushing until laboratory water testing confirmed zero detectable biocide or chemical contamination.

Outcome: Potable water purity was 100% restored. Full clinic re-opening was approved by the Colorado Department of Public Health with zero clinical personnel injuries.

Case Study 4: Data Center Conductivity Sensor Slime Blindness

Facility: A Tier-2 enterprise data center in Broomfield housing critical banking infrastructure.

The Emergency: Routine water testing revealed that cooling tower water had developed a thick, pea-green biological broth with high turbidity, yet the chemical dosing controller had dispensed zero biocide for over three weeks.

Investigation: The facility utilized contacting conductivity electrodes mounted in a bypass sampling loop.

When we unthreaded the sensor housing, the electrodes were completely encased in a 1/8-inch thick gelatinous sleeve of anaerobic bacterial slime and filamentous algae.

Because the slime insulated the electrodes, the controller registered a baseline conductivity of only 620 $\mu\text{S/cm}$.

The automated system was locked out because it was programmed not to blow down or dose chemicals if conductivity fell below 800 $\mu\text{S/cm}$ (assuming the tower was drained or newly filled).

Actual water conductivity was **3,900 $\mu\text{S/cm}$**, and total aerobic bacterial counts exceeded $10^6\text{ CFU/mL}$—a severe biological hazard.

The Solution:

1. We executed an emergency biological shock treatment using stabilized chlorine dioxide and biodispersants to dissolve the slime matrix.
2. We replaced the vulnerable contacting probe with a heavy-duty toroidal (electrodeless) conductivity sensor installed in a high-velocity self-cleaning sampling tee.
3. We programmed an automated flow switch interlock that triggers an alarm if sampling flow drops below 1.5 GPM.

Outcome: Bacterial populations plummeted to $< 10^2\text{ CFU/mL}$, with conductivity tracking accurately within ±1% of laboratory standards.

Case Study 5: Manufacturing Facility Solenoid Valve Debris Jam

Facility: An advanced aerospace composite tooling factory in Broomfield.

The Emergency: The plant manager noticed the monthly municipal water bill had spiked by $14,000. Municipal meter logs showed continuous high-volume water consumption 24 hours a day, even during weekend shutdowns.

Investigation: We audited the entire plumbing distribution network. We traced the continuous consumption to the central cooling tower blowdown line.

The 1.25-inch brass pilot-operated solenoid blowdown valve was humming loudly.

Water was discharging into the sewer at a continuous **32 gallons per minute**.

When we disassembled the solenoid body, we discovered a jagged shard of hard calcium scale—dislodged from the upper distribution header—wedged directly beneath the rubber diaphragm seat.

The valve was held permanently 30% open.

Over 45 days, the stuck valve had dumped over **2,000,000 gallons of treated municipal water** straight down the sewer drain!

The Solution:

1. We removed the pilot-operated solenoid valve and replaced it with a motorized stainless steel full-port ball valve with an integrated digital end-switch feedback loop.
2. We installed a 20-mesh Y-strainer with an automated flush blowdown upstream of the valve to capture scale flakes before they reach the seating surface.
3. We installed a pulse-output water meter on the blowdown line linked to the building automation system, programming an automated leak alert if blowdown flow exceeds 2,000 gallons in any 24-hour window.

Outcome: Water waste ceased immediately, saving the facility over $160,000 in projected annual water and sewage utility expenses.

7. Step-by-Step Cooling Tower Water Treatment Calibration Protocol

To ensure lasting thermal efficiency, zero scale formation, and complete environmental safety, commercial master plumbers and water treatment engineers execute this standardized calibration procedure:

Phase 1: Sensor Inspection & Calibration

1. Isolate the conductivity sensor sampling manifold. Remove the sensor and inspect for biofilm, algae, or calcium scaling.
2. Clean the probe using a 5% solution of sulfamic acid and a soft nylon brush. Rinse thoroughly with deionized water.
3. Perform two-point calibration using certified NIST-traceable conductivity standards (typically $1,413\text{ }\mu\text{S/cm}$ and $5,000\text{ }\mu\text{S/cm}$). Verify temperature compensation is set to $25^\circ\text{C}$ with a slope of $2.0\%/^\circ\text{C}$.

Phase 2: Blowdown Valve Actuation Verification

1. Manually override the controller to force a blowdown cycle. Observe valve actuation speed and full-stroke mechanical travel.
2. Verify blowdown drain line discharges freely into the sewer receptor without back-siphonage or splashing.
3. Force the valve closed and verify zero mechanical weeping at the outlet port.

Phase 3: Cycles of Concentration Optimization

1. Measure raw city makeup water conductivity and chloride levels ($[\text{Cl}^-]_{makeup}$).
2. Measure recirculating tower basin conductivity and chloride levels ($[\text{Cl}^-]_{tower}$).
3. Calculate actual operating cycles ($C = [\text{Cl}^-]_{tower} / [\text{Cl}^-]_{makeup}$).
4. Adjust conductivity setpoint to maintain optimal Front Range operating boundaries (typically 5.0 to 6.0 cycles, or $1,800\text{ to } 2,200\text{ }\mu\text{S/cm}$ depending on municipal source water).

Phase 4: ASSE 1013 Backflow Annual Certification

1. Connect a calibrated three-valve or five-valve differential pressure backflow test kit to the makeup water RPZ assembly.
2. Verify First Check Valve holds a minimum of **5.0 PSID** differential pressure.
3. Verify Differential Relief Valve opens before zone differential drops below **2.0 PSID**.
4. Verify Second Check Valve holds tightly against backpressure. Submit official certification test reports to the City of Broomfield Cross-Connection Control Division.

8. Preventative Maintenance Schedule for Cooling Tower Plumbing

Adhering to this disciplined maintenance timetable prevents catastrophic chiller shutdowns and high water bills:

• Weekly: Dip-test cooling tower basin conductivity with a calibrated handheld meter. Compare against the controller display; recalibrate if discrepancy exceeds ±5%. Inspect water level in basin to confirm float shutoff operates correctly. Inspect makeup water air gap.
• Monthly: Clean conductivity sensor electrodes or toroidal bore. Manually cycle the blowdown valve to clear sediment from seating faces. Inspect biocide metering pumps and chemical suction lines for leaks or air binding.
• Quarterly: Clean and flush the blowdown Y-strainer. Inspect cooling tower basin overflow piping for obstructions. Test automated high-water and low-water alarm contacts linked to the building automation system.
• Annually: Perform certified ASSE 5110 differential pressure testing on the makeup water RPZ backflow preventer. Drain, pressure-wash, and chemically disinfect the cooling tower basin following OSHA and ASHRAE Guideline 12 Legionella prevention standards. Eddy-current test chiller condenser tubes to verify zero internal pitting or scale buildup.