ASTM D1293

Cooling Tower Water

HVAC cooling towers recirculate water that concentrates dissolved minerals over time. pH outside the target range causes scale deposits (high pH) or corrosion of copper tubes and steel components (low pH). ASHRAE Guideline 12 recommends maintaining cooling tower water pH between 7.0 and 9.0 depending on the treatment program.

• Test frequency: daily or continuous inline monitoring
• Method B is standard for routine field checks
• pH drift signals chemical feed pump failure or blowdown malfunction

Concrete Mixing Water

ASTM C1602 governs mixing water for concrete. Water with pH below 4.5 or above 8.5 can alter cement hydration, affecting set time and compressive strength. ACI 318 references C1602 for acceptance of non-potable mixing water sources. D1293 is the test method used to verify pH compliance.

• Reclaimed water, well water, and wash water must be tested before use
• pH outside 4.5-8.5 requires strength comparison testing per C1602
• One-time qualification test per source, retest if source changes

Boiler Feedwater

Building heating systems with steam or hot water boilers require feedwater pH monitoring to prevent tube corrosion and scale. Low pH accelerates oxygen pitting in steel tubes. High pH causes caustic gouging and silica deposition.

• Target pH typically 8.5-9.5 for low-pressure boilers
• Chemical treatment (oxygen scavengers, pH adjusters) relies on accurate pH data
• Condensate return lines are especially vulnerable to low-pH corrosion

Stormwater Discharge

Construction sites disturbing one or more acres must obtain EPA NPDES (National Pollutant Discharge Elimination System) permit coverage. Most state permits require stormwater discharge pH between 6.0 and 9.0. Concrete washout, exposed soils, and dewatering operations can push pH outside limits.

• Test before each discharge event or per permit schedule
• Concrete washout water typically has pH 11-13 and must never enter storm drains
• pH violations can trigger stop-work orders and fines

Fire Suppression Systems

Standing water in wet-pipe sprinkler systems can become corrosive over time as dissolved oxygen reacts with steel pipe interiors. Monitoring pH of drained water during inspections helps assess internal corrosion risk. NFPA 25 inspection protocols increasingly reference water quality testing.

• pH below 6.5 in sprinkler water indicates active corrosion
• Microbiologically influenced corrosion (MIC) often accompanies low pH
• Water treatment or nitrogen inerting may be needed if pH trends downward

How often should pH be tested on a construction site?

It depends on the application. Stormwater discharge requires testing before each discharge event or per your NPDES permit schedule. Cooling towers need daily checks (or continuous monitoring). Concrete mixing water from a new source should be tested once for qualification, then retested if the source or season changes. Boiler feedwater is typically tested daily during the heating season.

Can I use pH test strips instead of a meter?

ASTM D1293 specifically requires an electrometric method (glass electrode pH meter), not colorimetric strips. Test strips are useful for quick screening but lack the precision for compliance reporting. A properly calibrated portable pH meter with automatic temperature compensation costs under $200 and meets Method B requirements for field use.

Which method should I use for field testing?

Method B. It allows single-buffer calibration and automatic temperature compensation, which is practical for jobsite conditions. Method A requires multi-buffer calibration at controlled temperatures and is designed for laboratory settings. If your permit or specification doesn't specify a method, Method B is appropriate for routine monitoring.

What causes concrete washout water to have such high pH?

Portland cement produces calcium hydroxide (Ca(OH)₂) during hydration, which is strongly alkaline. Fresh concrete washout water typically has pH between 11 and 13. This is well above the 6.0-9.0 range allowed by most stormwater permits. Washout water must be contained in designated areas and never discharged to storm drains. Neutralization with CO₂ or dilute acid is possible but requires careful monitoring.