Who this article is for: Authority users who manage discharge limits.

Discharge limits are the measurable thresholds your pretreatment program uses to define what an Industrial User can discharge at each outfall. Each limit targets a specific analyte (pollutant or parameter), specifies how compliance is measured (the limit type), and is assigned to an outfall.

A limit on its own defines the threshold. What gives it regulatory authority is its connection to a legal control — either a General Control (sewer use ordinance) or a Specific Control (discharge permit). SwiftComply tracks these connections through the Enforceability section on each limit, so you can see exactly which legal controls back each limit.

SwiftComply Pretreatment supports 24 limit types.

Point-in-time and average limits — available for every measurement category except mass and volume totals, such as concentration, temperature, or pH:

Total (Mass) limits — these require a mass unit, such as lbs or kg:

Total (Volume) limits — these require a volume unit, such as gallons:

TTO limits use the standard limit types, such as Daily Maximum and Monthly Average.

⚠️ Retired limit types: Split Sample Average and the older, unlabeled Total types — Daily Total, 4 Day Consecutive Total, Weekly Total, Monthly Total, and Annual Total — have been retired in favor of the (Mass) and (Volume) versions above. Existing limits that use them keep working, but they cannot be chosen for new limits.

💡 Tip: You cannot build a limit that does not make sense — the form only offers compatible combinations. Analyte, Limit Unit, and Limit Type filter each other, in any order. Pick a temperature analyte and you will only see temperature units and the point-in-time and average limit types; pick a mass unit first and only mass-compatible choices remain. Total (Mass) types need a mass unit and Total (Volume) types need a volume unit — neither accepts a concentration.

💡 Tip: Picking an analyte fills in its usual unit automatically. You can still change it. If that unit would not work with a limit type you already picked, the unit is left empty for you to choose a compatible one, and your limit type is kept as-is.

The compatibility rules are maintained in the product itself and grow as new measurement categories are added — recent additions include biological, turbidity, toxicity, and radioactivity units — so the form, not this article, is always the definitive list.

Every limit has a definition that determines how it is treated in the system:

This distinction is important: only Compliance limits have enforceability tracking. If you don't see the Enforceability section on a limit's detail page, the limit is set to Notification.

The rationale records the regulatory basis for the limit:

A CFR rationale records which federal categorical standard the limit comes from. The Rationale field is a searchable picker with two groups:

Citations read as the full standard, for example 40 CFR 405.14 Subpart A - Receiving Stations Subcategory (PSES). The citation ends in the standard type, either PSES or PSNS.

Selecting one records the rationale as CFR and stores the specific standard alongside it, so the limit carries its citation rather than only the category.

💡 The picker shows at most 30 matches at a time and says how many it found — 30 of 112 shown, keep typing to narrow — so keep typing if the standard you want is not listed. If a limit already cites a standard that has since been retired, it stays selected, so editing another field does not clear it.

Limits are created at the outfall level. Their enforceability comes from connections to legal controls. There are two ways limits get connected:

You manually connect a Compliance limit to a General Control from the limit's detail page using the + General Control button. This is how you establish that a limit is backed by a sewer use ordinance or other broad regulation. A limit can be connected to multiple General Controls.

General Controls do not have expiration dates the way permits do — they remain in effect until explicitly terminated. A limit connected to a General Control is enforceable as long as that General Control is active.

For the step-by-step process, see Managing Discharge Limits.

Limits are added to a permit in Step 2 (Limits) of the permit wizard. Click Add Limit and choose Select Available Limits to add limits already on the IU's outfalls, or New Limit to create one. This step requires a permit template that includes a limits system table (such as Compliance Limits, Notification Limits, or Limits and Requirements Table).

To take a limit off a permit, select its row in Step 2 and click Remove. Removing a limit from the permit does not delete or modify the limit itself — it only removes it from that particular permit. The limits added in Step 2 appear in the template's limits tables in Step 4 (Fill Form).

A limit connected to a permit is enforceable for the duration of that permit's effective and expiration dates. Once the permit expires or is terminated, the limit is no longer enforced under that permit. If the IU is reissued a new permit, the limit would be connected to the new permit through the same permit creation process.

For details on system tables and the permit creation workflow, see Understanding Permit Templates and System Tables and How Permits and Sample Report Configurations Work Together.

A single limit can be connected to any combination of General Controls and Specific Controls simultaneously. For example, a BOD limit might be backed by both the sewer use ordinance (General Control) and the IU's discharge permit (Specific Control). The Enforceability table on the limit detail page shows the status and dates for each connection.

Limits are assigned at the outfall level. To view limits:

Limits can also be viewed under a General Control's detail page in the Discharge Limits expandable section.

Q: What is the difference between Compliance and Notification limits?
A: Compliance limits are legally enforceable and can be connected to legal controls through the Enforceability section. Notification limits are monitoring thresholds that do not have enforceability tracking.

Q: Can one outfall have multiple limits for the same analyte?
A: Yes. You can have different limit types for the same analyte on the same outfall — for example, both a Daily Maximum and Monthly Average limit for BOD.

Q: How do limits get into a permit?
A: Limits are added in Step 2 (Limits) of the permit wizard, which requires a permit template that includes a limits system table. They are enforced under the permit once it is signed.

Q: What happens to a limit's enforceability when a permit expires?
A: The limit is no longer enforced under that permit. If the limit is also connected to a General Control, it remains enforceable under that control. The limit itself is not modified or deleted.

Q: What units are available for limits?
A: Over 20 units are available including Milligrams per liter, Micrograms per liter, Degrees C, Degrees F, SU, Pounds per day, Pounds, Gallons, Gallons per day, and more. Available units depend on the selected analyte and limit type.