What EPA method is required for pH compliance monitoring?

EPA Method 150.1 for individual grab samples and EPA Method 150.2 for continuous monitoring, both electrometric and both listed at 40 CFR 136.3 Table IB under parameter 28, hydrogen ion. Standard Methods 4500-H+ B, ASTM D1293 methods A or B, and USGS I-1586-85 are listed alongside them as approved alternatives. The same methods are acceptable for water quality parameter monitoring under the Lead and Copper Rule.

What is the 15-minute rule for pH samples?

A grab sample collected for pH compliance must be analyzed within 15 minutes, per 40 CFR Part 136 Table II. This is the requirement that most often defeats an otherwise good monitoring program, because it is a constraint on logistics rather than on instrumentation. If the laboratory is more than a few minutes from the sampling point, a benchtop meter in that laboratory cannot satisfy the method no matter how accurate it is. Document compliance by recording both collection time and analysis time, typically on the chain-of-custody.

Can pH be averaged or reported as a monthly average?

No. Because pH is a logarithmic scale, pH limits cannot be established as monthly average values or ranges, and effluent limitations are always applied as instantaneous limits. For the same reason the Technical Review Criteria used to evaluate other parameters do not apply to pH — calculating a percentage over or under a pH limit would be mathematically incorrect on a logarithmic scale.

Can I use composite samples for pH?

No. Composite samples may not be used for pH compliance monitoring under 40 CFR 403.12(g)(3). Only grab samples are acceptable. Continuous monitoring also satisfies the requirement, because a continuous meter records individual instantaneous readings rather than a blended value.

What is the minimum pH for discharge to a sewer?

Federal pretreatment standards at 40 CFR 403.5(b)(2) prohibit discharges that cause corrosive structural damage, and in no case below pH 5.0, unless the treatment works is specifically designed to accommodate such discharges. There is no federal prohibited upper threshold, though most Control Authorities set a local upper limit between 10 and 11.5, and categorical users may have applicable EPA standards. Your local limits and discharge permit govern and are frequently more stringent than the federal floor.

What pH electrode should I use for industrial wastewater?

A full 0 to 14 range, double junction, refillable electrode with a high-flow junction is the general recommendation for dirty or aggressive samples. The double junction reference reduces drift and protects against poisoning by sulfides, proteins, and heavy metals common in industrial streams. Sealed gel electrodes are lower maintenance but have shorter life and clog more readily in dirty water, making them reasonable for clean process water and poor for wastewater. Epoxy bodies survive plant handling better than glass.

How often should a compliance pH meter be calibrated?

Common practice is a daily two-point buffer check for instruments in active service, plus annual calibration by an ISO/IEC 17025-accredited laboratory against NIST-traceable standards, and always after electrode replacement. Your actual interval should be defined and justified in your quality management system or SOP rather than inherited from a generic recommendation. Insist that accredited calibration certificates include as-found data, not just as-left — as-found is what tells you whether measurements taken since the last calibration were valid.

Field Guide — Wastewater & Compliance

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pH Meters for Commercial Water Use: EPA Methods, the 15-Minute Rule, and What an Inspector Asks For

Q: Does the 7 hour 26 minute pH excursion allowance apply to my sewer discharge?

No, and this is a costly misreading. The excursion allowance at 40 CFR 401.17 — pH maintained between 6.0 and 9.0, not exceeded for more than 7 hours and 26 minutes in a calendar month with no individual excursion over 60 minutes — applies only to direct dischargers continuously measuring pH under an NPDES permit. It does not apply to indirect discharges to a POTW regulated under Part 403. Unless the treatment works is documented as acid tolerant, any excursion below pH 5.0, including an instantaneous one of any duration, is a pretreatment standard violation.

Reviewed by Lawrence Quarles, Alabama Grade IV Wastewater Treatment Operator · August 2026

The most expensive mistake in commercial pH monitoring is buying an instrument that reads pH beautifully and failing the compliance requirement anyway — because the requirement was never really about the instrument. Under EPA Method 150.1 a grab sample must be analyzed within 15 minutes. Miss that window and the data is not compliant regardless of how good the meter is. This guide covers the federal framework that governs pH data used for reporting, the procedural rules that trip people up, how to choose between grab and continuous monitoring, and the records an inspector actually asks for.

Compliance is a procedure with an instrument in it, not an instrument with a procedure around it.

Start here: what is your pH data for?

Reporting to a regulator

NPDES permit, pretreatment discharge permit, or drinking water compliance. The governing constraint is the approved analytical method and its procedural requirements. The instrument must satisfy the method, and your records must prove that it did. Everything in Parts 1 and 4 below applies to you.

Process control only

Cooling tower, boiler, chemical dosing, product quality. The constraint is fitness for purpose. No approved-method requirement, but the consequence of bad data is equipment damage and wasted chemical spend rather than an enforcement action.

Both

The compliance requirement governs. Buy to the stricter standard. A meter that satisfies 150.1 will also serve process control; the reverse is frequently not true.

Approved methods
The 15-minute rule
Four procedural rules
The limits themselves
The 40 CFR 401.17 trap
Grab vs. continuous
Instrument types
Electrode selection
Calibration discipline
Cooling towers and boilers
Specification checklist
Common mistakes
FAQ

Approved methods

Clean Water Act analytical methods are listed at 40 CFR 136.3 Table IB. For pH — parameter 28, hydrogen ion — the approved procedures are all electrometric:

Method	Application	Where approved
EPA Method 150.1	pH by individual grab sample, electrometric, non-continuous	40 CFR 136.3 Table IB, parameter 28
EPA Method 150.2	pH, continuous monitoring, electrometric (December 1982)	40 CFR 136.3 Table IB — approved for continuous monitoring of industrial wastewaters
Standard Methods 4500-H+ B	Electrometric	Listed alongside 150.1 in Table IB
ASTM D1293 (A or B)	Electrometric	Listed alongside 150.1 in Table IB
USGS I-1586-85	Electrometric	Listed alongside 150.1 in Table IB
The same set — 150.1, 150.2, ASTM D1293 and SM 4500-H+ B — is acceptable for pH as a water quality parameter under the Lead and Copper Rule, which matters for facilities operating their own public water system or performing corrosion control monitoring.

Note that all approved methods are electrometric. Colorimetric pH — test strips, comparator kits, indicator solutions — is not an approved method for compliance reporting. Those have a legitimate place in screening and process checks, but a number produced by a color comparison cannot be reported to a regulator.

The 15-minute rule

A grab sample collected for pH compliance must be analyzed within 15 minutes. This comes from 40 CFR Part 136 Table II, and it is a constraint on logistics, not on instrumentation. It is the single most common way a well-equipped facility produces non-compliant data.

Think through what this means physically. If your outfall is at the back of the property and your laboratory is in the front office, the walk itself may consume the window. A benchtop meter with 0.001 pH resolution sitting in that laboratory cannot satisfy the method if the sample takes twenty minutes to reach it. A mid-grade portable meter carried to the sampling point can.

That is why the 15-minute rule usually decides the instrument category before any accuracy specification does:

Situation	What the 15-minute rule implies
Sampling point far from lab	Portable field meter, calibrated and carried to the sample. This is the common answer.
Lab immediately adjacent to sampling point	Benchtop is viable — but time the walk before assuming it.
Multiple sampling points on rounds	Portable, with calibration verified at the start of the round and the timing of each analysis logged.
Continuous discharge, tight limits	Inline analyzer under 150.2 — the 15-minute question disappears entirely because there is no sample transport.

Document the window, don't just meet it. Meeting the requirement and being able to prove you met it are different things. Record both collection time and analysis time — typically on the chain-of-custody — so the elapsed interval is visible on the record. An inspector reviewing your data will look for it, and a record showing only one timestamp cannot demonstrate compliance with the hold time.

Four procedural rules

Rule	Detail	Citation
Grab samples only	Composite samples may not be used for pH compliance monitoring. Continuous monitoring satisfies the requirement because continuous meters record individual instantaneous readings rather than a blended value.	40 CFR § 403.12(g)(3)
15-minute analysis window	Grab samples must be analyzed within 15 minutes. Document with collection and analysis times.	40 CFR Part 136 Table II
pH cannot be averaged	Because the scale is logarithmic, pH limits cannot be established as monthly average values or ranges. Effluent limitations are always applied as instantaneous limits.	EPA pretreatment pH guidance
TRC does not apply to pH	The Technical Review Criteria are specifically excluded for pH, because calculating a percentage over or under a limit is mathematically incorrect on a logarithmic scale.	EPA pretreatment pH guidance

The averaging rule deserves a moment's thought, because it changes how you should read your own data. A day with readings of 5.0, 7.0, and 9.0 does not "average to 7.0" in any meaningful sense — pH 5.0 is a hundred times more acidic than pH 7.0, and if 5.0 is your floor, that reading is a violation on its own. Any spreadsheet that computes a mean pH column is producing a number that has no regulatory standing and no chemical meaning.

The limits themselves

Context	Limit	Citation
Discharge to a POTW	Prohibits discharges causing corrosive structural damage, and in no case below pH 5.0, unless the works is specifically designed to accommodate such discharges	40 CFR § 403.5(b)(2)
Upper limit to a POTW	No federal prohibited upper threshold. Most Control Authorities set a local upper limit between 10 and 11.5; categorical users may have applicable EPA standards	Local limits
Direct discharge under NPDES	Where effluent guidelines apply, maintain pH between 6.0 and 9.0, not exceeded more than 7 hours 26 minutes in any calendar month, no individual excursion over 60 minutes	40 CFR § 401.17
Hazardous waste characteristic	An aqueous solution at pH ≤ 2.0 or ≥ 12.5 is a characteristic hazardous waste	40 CFR § 261.22(a)(1)
Reporting a violation	Notify the Control Authority within 24 hours of becoming aware, resample, and submit repeat results within 30 days	40 CFR § 403.12(g)(2)
Chronic significant noncompliance	66% or more of pH measurements in a six-month period below 5.0 or outside applicable limits	EPA pretreatment guidance

The hazardous waste line is worth knowing even if you never approach it. A tank of spent acid or caustic sitting at pH 1.5 or 13 is not simply a pH problem — it is a characteristic hazardous waste under RCRA, with a completely different regulatory regime governing storage, manifesting, and disposal. Facilities running acid cleaning, metal finishing, or CIP chemistry should know where their strongest streams actually sit.

The 40 CFR 401.17 trap

This is the most consequential misreading in commercial pH compliance, and it is easy to fall into because the regulation sounds like exactly what a facility operator wants to hear.

40 CFR 401.17 does not apply to indirect dischargers. The 7-hours-26-minutes monthly excursion allowance applies only to direct dischargers continuously measuring pH under an NPDES permit. It does not apply to discharges to a POTW regulated under Part 403. Unless your treatment works is documented as acid tolerant, any excursion below pH 5.0 — including an instantaneous one of any duration — is a pretreatment standard violation.

The practical damage is in how it shapes system design. A facility that believes it has a monthly excursion budget will size neutralization, set alarm thresholds, and write its response procedures around a tolerance it does not have. If you discharge to a sewer, design for zero excursions below the floor, not for a permitted quantity of them.

Quick test: Do you discharge to a municipal sewer (indirect, Part 403) or to a water of the United States under an NPDES permit (direct)? If the answer is the sewer, 401.17 is not your rule. Your Control Authority's local limits and your discharge permit are.

Grab vs. continuous

Factor	Grab sampling	Continuous monitoring
Regulatory method	EPA 150.1	EPA 150.2
Compliance evidence	A discrete result at a discrete time	A record of individual instantaneous readings, which satisfies the grab requirement
Excursion detection	Only catches what happens during sampling	Catches everything — a double-edged benefit
Response capability	None. You learn afterward.	Enables alarm-driven mitigation before an excursion becomes reportable
Labor	Ongoing, per sample	Front-loaded, then maintenance
Best when	Discharge is stable and infrequent; permit frequency is low	Discharge is variable, limits are tight, or an excursion carries serious consequences

Continuous monitoring records your bad days too. This is worth confronting honestly before installing. A continuous record captures every excursion, and each one must be reported to the Control Authority for determination of the appropriate enforcement response, just as with any other permit exceedance. That is not an argument against continuous monitoring — it is an argument for pairing it with alarms and a real mitigation capability, so excursions get prevented rather than merely documented in high resolution.

The best buying guidance in the regulation is the alarm recommendation. EPA recommends that Control Authorities require facilities to install and maintain a continuous pH monitoring alarm, specifically so personnel can observe, mitigate, and notify on readings approaching limits. When specifying a continuous system, treat programmable alarm setpoints, relay outputs, and remote notification as required features rather than options. The regulator has effectively said so.

Two administrative points on continuous systems. EPA has not established required recording intervals — Control Authorities are directed to set intervals producing data representative of discharge conditions, so ask yours rather than guessing. And if you monitor more frequently than required using the prescribed procedures, all results must be included in the periodic report under § 403.12(g)(6). Extra monitoring is not private monitoring.

Instrument types

Type	Typical use	Compliance suitability
Pocket / pen tester	Spot checks, screening, informal monitoring	Generally unsuitable for compliance work — limited calibration logging, low resolution, short electrode life
Portable field meter	Grab sampling for compliance, multi-point rounds, troubleshooting	Meets approved-method requirements when properly calibrated and documented. Portable to the sample, which is what makes the 15-minute rule achievable
Benchtop laboratory meter	Laboratory analysis, highest accuracy, method development	Best resolution and stability, full calibration logs and export — but the sample must come to the meter, which puts the 15-minute window under pressure
Inline / process analyzer	Continuous monitoring under 150.2, closed-loop dosing control	Continuous record, alarms, control outputs, no sampling labor. Highest cost; needs a real maintenance program
Multiparameter sonde	Simultaneous pH, conductivity, DO, ORP, temperature	Efficient for surveys and multi-parameter permits. More sensors to calibrate; one failure can pull the whole deployment

Instrument reviews on this site, by category:

Pocket testers — Hach Pocket Pro and Pocket Pro+, YSI pH10A EcoSense. Screening and process checks.
Portable field — Apera PH60 (AI311), waterproof with a replaceable probe and pH/mV/ORP/temperature.
Benchtop — Apera PH700 (AI501), ±0.001 pH with a 50-point log.
Multiparameter — Myron L Ultrameter II and YSI Pro20.

Calibration logging is audit evidence, not a convenience feature. The distinguishing capability between a screening instrument and a compliance instrument is usually not accuracy — it is whether the meter stores and exports calibration history including slope, offset, buffer values, and timestamps. That log is what you hand an inspector. A meter that reads to 0.01 pH but keeps no record leaves you reconstructing your calibration history from a paper notebook.

Electrode selection

The electrode is where commercial water differs most from laboratory work, and it is also the dominant recurring cost — electrodes are consumables with a life measured in months to a couple of years depending on service.

Feature	Why it matters in commercial water
Full 0–14 range	Industrial wastewater and cleaning chemistry span the scale. A limited-range electrode is a false economy
Double junction reference	Reduces drift, stabilizes faster, and protects the reference from poisoning by sulfides, proteins, and heavy metals common in industrial streams
Refillable, high-flow junction	Better in dirty samples than sealed gel; requires fill solution maintenance
Sealed gel	Lower maintenance, shorter life, prone to junction clogging in dirty water. Reasonable for clean process water, poor for wastewater
Body material	Epoxy survives plant handling better than glass; glass is better for chemical resistance and elevated temperature
Pressure and temperature rating	Inline sensors must match the process — check both

Sulfide poisoning of the reference junction is worth specific mention, because facilities dealing with hydrogen sulfide are exactly the ones likely to be measuring pH frequently. If your streams carry sulfide, the double junction is not optional — see the sulfur and hydrogen sulfide guide for the chemistry.

Calibration discipline

Full protocol, buffer handling, and troubleshooting live in the pH meter calibration guide. What follows is the compliance-specific layer on top of it.

Slope is the health indicator

A pH electrode does not fail suddenly. The glass membrane ages, the slope drops, and readings drift slowly — which is precisely what makes it dangerous. An electrode that is "close enough" for months can erode confidence in an entire dataset once the drift is finally caught, forcing a costly look-back investigation across every measurement since the last known-good calibration.

Parameter	What it is	Acceptance guidance
Slope	mV response per pH unit against the Nernstian ideal of about −59.16 mV/pH at 25 °C, as a percentage of theoretical	Commonly 95–105%. One manufacturer specifies 92–102%; one GMP reference flags outside 90–110% as indicating replacement
Offset	Asymmetry potential — the reading in pH 7 buffer, ideally 0 mV	One GMP source: within ±20 mV good, 20–30 mV suggests cleaning, persistent deviation suggests replacement. One manufacturer specifies ±59 mV
Acceptance ranges differ between sources because they reflect different acceptance philosophies, not a factual conflict. Your instrument manufacturer's specification and your own SOP govern — and whichever you adopt should be written down rather than assumed.

Log slope and offset at every calibration and trend them. A declining slope tells you an electrode is dying weeks before it gives you bad data you act on. That trend is simultaneously your replacement forecast and the evidence an auditor wants.

As-found data is the record that matters

An accredited calibration certificate reports the instrument's condition on arrival (as-found) and after adjustment (as-left). As-found is what tells you whether measurements taken since the last calibration were valid — it is the first thing an inspector asks for and what determines whether you need a look-back investigation. When specifying calibration services, require as-found data. A certificate reporting only as-left tells you nothing about your historical data.

Typical practice is a daily two-point buffer check for instruments in active service, annual calibration by an ISO/IEC 17025-accredited laboratory against NIST-traceable standards, and always a fresh calibration after electrode replacement. Buffers should bracket your expected range and always include pH 7 to establish the offset — if your samples run at pH 8.6, calibrate with 7 and 10, not 4 and 7.

Cooling towers and boilers

HVAC water is the process-control side of the decision tree — no approved-method requirement, different failure mode.

Parameter	Typical target	Why
Cooling tower pH	Commonly 7.0–8.5	Below ~7.0 accelerates acidic corrosion of copper condenser tubes and carbon steel piping; above ~9.0 promotes calcium carbonate scale on hot surfaces
Langelier Saturation Index	Often −0.5 to +0.5; some industrial practice targets 0.0 to +0.5	Positive indicates scaling tendency, negative indicates corrosion tendency. pH is one input
Companion measurements	Conductivity, alkalinity, hardness, cycles of concentration	pH alone cannot tell you whether water is scaling or corrosive. LSI needs the others
Targets vary by system metallurgy and treatment program; your water treatment vendor's program governs.

In HVAC water, pH is a control input rather than a control objective. Nobody cares about cooling tower pH for its own sake — it matters because it drives calcium carbonate solubility and therefore the scaling-versus-corrosion balance. The instrumentation consequence is that a pH meter alone is not enough: budget for conductivity and alkalinity measurement in the same program. See measuring TDS and conductivity for the companion parameter.

Two cautions. First, pH is not a Legionella control parameter. Good pH numbers do not substitute for a water management program. Second, boiler water must be cooled through a sample cooler before measurement — both for operator safety and because pH is temperature dependent and glass electrodes have temperature limits. Measuring a hot sample directly gives a wrong number and destroys the electrode.

Specification checklist

Item	What to specify
Application	Compliance reporting, process control, or both. Decides everything downstream
Method conformance	If compliance: must support EPA 150.1 or 150.2 as applicable
Range	Full 0–14 for wastewater; narrower only for well-characterized process streams
Resolution and accuracy	0.01 pH resolution is standard for compliance work. Match accuracy to your permit's limit precision
Temperature compensation	Automatic, with the ATC element verified against a reference thermometer during calibration
Calibration logging	Stores and exports slope, offset, buffer values, timestamps. This is your audit evidence
Data output	Timestamped datalogging and export. For continuous: 4–20 mA, Modbus or equivalent
Alarms (continuous)	Programmable setpoints, relay outputs, remote notification — per EPA's recommendation
Ingress protection	Match the environment. Sampling points and mechanical rooms are wet, dirty, and washed down
Electrode type	Double junction refillable for dirty or aggressive samples
Spares and consumables	Confirm electrode availability and price before purchase. The electrode is the recurring cost, not the meter
Service	Availability of ISO/IEC 17025-accredited calibration, in-lab or on-site

On total cost of ownership: the instrument is usually the smallest lifetime line item for a meter in regular service. Electrodes dominate, followed by NIST-traceable buffers and storage solution, annual accredited calibration, and the labor of daily checks and logging. And then there is the cost of being wrong — a drifted electrode discovered late can trigger a look-back across every measurement since the last good calibration.

Common mistakes

Mistake	Consequence
Missing the 15-minute grab window	Data is not compliant with EPA 150.1 regardless of instrument quality
Compositing samples for pH	Prohibited under 40 CFR § 403.12(g)(3)
Averaging pH	Logarithmic scale; limits are always instantaneous
Applying 401.17 excursion allowances to a sewer discharge	401.17 is for direct NPDES dischargers only. For pretreatment, any excursion below 5.0 is a violation
Buffers that don't bracket the sample	Extrapolating outside the calibration range degrades accuracy where it matters most
Omitting pH 7 from calibration	pH 7 establishes the offset. Without it you have slope with no zero point
Storing the electrode in deionized water	Leaches the reference junction and shortens electrode life dramatically
Not logging slope and offset	Loses the only early warning of electrode failure, and the evidence an auditor wants
Accepting a certificate without as-found data	Cannot assess whether historical measurements were valid
Measuring hot boiler water directly	Wrong reading and a destroyed electrode
Treating pH as sufficient for cooling tower control	pH is an input to LSI, not the whole picture
Continuous monitoring without alarms or mitigation	Creates a complete record of excursions you could not respond to
Buying on instrument price alone	Electrodes and buffers dominate lifetime cost

Quick reference

Grab method

EPA 150.1

Continuous method

EPA 150.2

Hold time

15 minutes

Pretreatment floor

pH 5.0

Typical local upper

10 to 11.5

Hazardous waste

≤2.0 or ≥12.5

Violation notice

24 hours

Chronic SNC

66% in 6 months

SIU reporting

Min. 2×/year

Nernstian ideal

−59.16 mV/pH

Healthy slope

~95–105%

Cooling tower pH

7.0–8.5

FAQ

What EPA method is required for pH compliance?

EPA 150.1 for grab samples, EPA 150.2 for continuous monitoring, both at 40 CFR 136.3 Table IB parameter 28. SM 4500-H+ B, ASTM D1293, and USGS I-1586-85 are listed alternatives. All are electrometric — test strips and colorimetric comparators are not approved methods for reporting.

What is the 15-minute rule?

A grab sample for pH must be analyzed within 15 minutes per 40 CFR Part 136 Table II. It is a logistics constraint, and it usually decides between a portable meter at the outfall and a benchtop in a distant lab. Record both collection and analysis times to prove you met it.

Can I report a monthly average pH?

No. pH is logarithmic, so limits cannot be established as averages or ranges and are always applied as instantaneous limits. The Technical Review Criteria are likewise excluded for pH.

Can I use a composite sampler for pH?

No — prohibited under 40 CFR § 403.12(g)(3). Grab samples only. Continuous monitoring is acceptable because it records individual instantaneous readings.

What is the minimum pH I can discharge to the sewer?

Federal pretreatment standards prohibit discharge below pH 5.0 unless the works is specifically designed for it, per 40 CFR § 403.5(b)(2). There's no federal upper threshold, but most Control Authorities set one between 10 and 11.5. Your local limits govern and are often stricter.

Does the 7 hour 26 minute excursion allowance apply to me?

Only if you're a direct NPDES discharger continuously measuring pH. It does not apply to sewer discharges under Part 403. For pretreatment, any excursion below 5.0 — even instantaneous — is a violation.

Is a pocket pH tester good enough for compliance?

Generally no. The limitation isn't usually raw accuracy — it's calibration logging, resolution, and electrode life. A compliance instrument needs to store and export calibration history including slope, offset, buffer values, and timestamps, because that log is your audit evidence.

What electrode should I use for wastewater?

Full 0–14 range, double junction, refillable, high-flow junction. The double junction protects the reference from sulfides, proteins, and heavy metals. Sealed gel electrodes are fine for clean process water and poor for wastewater.

Related Guides and Instrument Reviews

Sources: U.S. Environmental Protection Agency, "Pretreatment Program pH Requirements for Industrial Users," December 2024 — the primary source for the regulatory sections. · 40 CFR § 136.3 Table IB, List of Approved Inorganic Test Procedures, parameter 28 (hydrogen ion). · 40 CFR Part 136 Table II (sample hold times). · 40 CFR §§ 401.17, 403.5(b)(2), 403.12(g)(2), 403.12(g)(3), 403.12(g)(6), 261.22(a)(1). · EPA Methods 150.1 and 150.2. · Standard Methods 4500-H+ B; ASTM D1293; USGS I-1586-85. · USP <791> pH via manufacturer implementation guidance. · Electrode slope and offset acceptance criteria from ISO/IEC 17025-accredited calibration laboratories and GMP calibration references; ranges differ between sources and are shown rather than reconciled. · Cooling tower pH and LSI targets from commercial water treatment industry references; targets vary by metallurgy and treatment program.

This guide summarizes federal requirements and does not impose or interpret legally binding obligations. State and local authorities may impose more stringent limits, and in pretreatment they commonly do. Your discharge permit governs. For compliance questions, your Control Authority or Regional/Authorized State pretreatment coordinator is the correct contact.