Check wastewater quantity before committing to expansion
This calculator applies Korean 2026 rules to one ordinary wastewater discharge facility.
When a small manufacturing or washing business moves or expands, treating all purchased water as wastewater can overstate equipment and staffing budgets, while an average-day estimate can miss the legal classification basis.
The worksheet separates fresh supplies, deductions, process-generated water and treatment inflows, then compares the current site with the entire post-expansion site.
Decisions this worksheet supports
- Reconcile the peak-day discharge quantity and reference class 1–5.
- Identify a planned class change and the distance to the next larger discharge bracket.
- Save the quantity ledger for authority review of installation/change procedures and revised equipment or treatment quotations.
Select the annual maximum-discharge day
Note 1 of Annex 13 to Korea’s Water Environment Conservation Act Enforcement Decree uses the day with the highest discharge during the year.
The highest water-consumption day may differ because of storage, washing schedules and process operations.
Do not combine one day’s supply with another day’s deductions: review daily records and assemble all quantities on the same daily basis.
Existing operation and expansion
A represents the current peak-day ledger; B represents the whole post-expansion peak-day plan.
Copy A to B and revise affected quantities, but do not enter only the incremental water in B.
The tool does not search a year of records to identify the peak day for you.
First-installation permit
Note 3 uses expected water consumption in the business plan for a first discharge-facility installation permit.
Record planned equipment, operating and washing assumptions with their source instead of inventing operating history.
Planned quantities remain subject to authority review.
Separate fresh supply W from internal reuse R
W equals mains water plus industrial water plus groundwater plus other fresh supplies.
Use the other-supply field for river water, seawater and other incoming sources, keeping their supporting records.
Every quantity is in m³/day; 1 m³ equals 1,000 litres.
Convert litres or hourly flows to the actual whole-day volume before entry.
Reuse is a separate reference ledger
Distinguish fresh intake from internal process reuse and water returned through a defined pipe to production before final discharge.
This worksheet leaves internal reuse R out of W at the outset.
Subtracting R again would exclude the same water twice.
If a meter includes circulating flow, separate it from fresh intake first; unverified pipes or ledger exclusions keep the result pending.
Split domestic and cooling use into totals and treatment returns
Total domestic use L and indirect cooling use C are allocations within W.
Lt and Ct record the portions entering pollution-prevention treatment.
Neither return may exceed its source total, and these quantities must not also appear in another non-discharge deduction.
Deduct only the portion outside treatment
Domestic deduction = L − Lt
Cooling deduction = C − Ct
If domestic use is 20 and 5 enters treatment, its deduction is 15.
If indirect cooling use is 30 and 10 enters treatment, its deduction is 20.
Recording both quantities prevents the entire use from being deducted while its treatment return is omitted.
Distinguish deductions D0 and treatment inflows I and E
Boiler, product, evaporation and other deductions
D0 contains boiler water outside treatment, water retained in products, process evaporation and other recognized non-discharge quantities.
Boiler blowdown entering treatment does not belong in this deduction merely because it came from a boiler.
Keep product moisture and evaporation evidence separate and non-overlapping.
Water entering treatment
Dilution water, domestic water, indirect cooling water, site-cleaning water and raw-material-yard leachate are included when treated in the pollution-prevention facility.
I records other treatment inflows already counted in W, excluding Lt and Ct, and is not added again.
E records only additional treatment inflows outside both W and process generation G.
G represents water generated by the process itself, such as water associated with raw materials or reactions, that is not already counted in W.
Do not add ordinary washing water a second time as process generation.
Each source is recorded once; if L+C+D0+I exceeds W, the worksheet holds the result for an allocation or unit check.
The wastewater water-balance formulas
Account for every flow once
D = L − Lt + C − Ct + D0
Q = W − D + G + E
This ledger expresses the Annex 13 supply-minus-deductions-plus-generation formula while retaining treatment inflows.
Lt, Ct and I are already within W, so they are not added to Q again.
R is reference only and is not subtracted again from W.
An inconsistent balance is held for correction rather than clipped to zero.
Each numeric input supports 0–1,000,000 with up to six decimal places.
This is a technical input range rather than a legal permitted discharge limit.
The engine uses integer millionths of a cubic metre and classifies before display rounding.
Numerical precision does not turn an unsupported estimate into a legally recognized deduction.
Korean site classes and discharge boundaries
Annex 13 site classes by daily wastewater discharge| Class | Lower bound m³/day | Upper bound m³/day |
|---|
| 1 | 2,000 inclusive | No upper bound |
| 2 | 700 inclusive | Below 2,000 |
| 3 | 200 inclusive | Below 700 |
| 4 | 50 inclusive | Below 200 |
| 5 | Facilities outside classes 1–4 | Below 50, reference |
Exactly 50, 200, 700 and 2,000 m³/day enter classes 4, 3, 2 and 1 respectively.
The distance to the next boundary is not an inclusive allowance to increase discharge.
For Q = 65, the distance to 200 is 135; adding 135 reaches class 3.
Class 1 has no further class boundary.
Worked current-versus-expansion example
The example button loads fictional quantities for learning, rather than typical site data or a recommended design.
Both plans use L20, Lt5, C30, Ct10, boiler15, product10, evaporation5, other0, I10, G8, E2 and R40.
D is 15+20+15+10+5=65, and R40 is not subtracted a second time.
Fictional current A versus full post-expansion B, quantities in m³/day| Metric | Current A | Expanded B |
|---|
| Fresh supply W | 120 | 260 |
| Deduction D | 65 | 65 |
| Discharge Q | 65 | 205 |
| Reference class | 4 | 3 |
| Distance to next boundary | 135 | 495 |
| Entered capacity K | 80 | 180 |
| Simple margin K−Q | 15 | −25 |
| Simple shortage | 0 | 25 |
A is 120−65+8+2=65, while B is 260−65+8+2=205; B−A is 140 m³/day.
The reference class changes from 4 to 3, and B has a simple capacity shortage of 25.
Take the full expansion plan and treatment flow paths to the environmental authority and request a review of equipment capacity and treatment processes.
How to use the worksheet and prepare evidence
- Confirm ordinary facility scope and special conditions, then select the annual peak-discharge day or first-installation planning basis.
- Use meters and process ledgers to split fresh supply, deductions and inflows for the same day.
- Enter a verified zero for absent flows.
Blank quantities remain unknown.
- Check total domestic/cooling use, treatment returns, I within W and E outside W and G for overlap.
- For R above zero, verify the piped return to production before final discharge and its exclusion from fresh supply.
- Enter the whole post-expansion site and capacity with the same comparison scope; inspect results and pending reasons.
- Save TXT with the basis date, deduction evidence, pipe drawings and expansion plan for authority and provider review.
Numeric fields accept commas and decimals and preserve editing drafts, so you can clear a field or edit its decimal point.
Editing invalidates the previous result; calculate again before saving.
TXT is generated in your browser and does not submit the worksheet to an authority.
Use cases for expansion, relocation and treatment quotes
Adding washing equipment
A new washing line can change both consumption and the day when stored washwater is released.
Reconstruct the concentrated washing day rather than adding fresh-water use to an ordinary production day.
If planned Q decreases, check whether the storage, transfer schedule or selected basis also changed.
Moving a factory or requesting outsourced treatment
Different pipes at the new site can route domestic or cooling water into treatment.
Unchanged water consumption can therefore yield different deductions, treatment flow and reference class.
For outsourced treatment quotes, reconcile the ledger basis with the actual scope of transferred, received and treated quantities.
Pending states and the limits of capacity comparisons
Unverified evidence remains unresolved
Unknown facility scope, peak-day basis, ledger evidence, required quantities or reuse pipes keep Q and class pending.
Returns above their source totals or overlapping allocations within W also hold the result.
If only optional capacity K is unknown, a valid Q and class remain available while capacity differences stay unknown.
Simple margin is K−Q; simple shortage is max(0, Q−K).
These quantities do not assess instantaneous loads, concentrations, operating hours, retention time, separate treatment trains or design reserve.
Self-monitoring duties, specified hazardous substances, zero-discharge and integrated permits, staffing qualifications, nationwide site eligibility and sewer connection contributions are outside scope.
Verify facility-specific conditions and authority evidence requirements before transferring these figures to an official filing.
Frequently asked questions
Is mains-water consumption the same as wastewater discharge?
No.
Include industrial water, groundwater, river water, seawater and other fresh supplies as well.
Separate the recognized domestic, cooling, boiler, product, evaporation and other non-discharge deductions, without deducting water that enters treatment.
A water bill alone does not establish every inflow or deduction.
Can I divide monthly consumption by operating days?
That produces an average rather than the annual maximum-discharge day required by Annex 13.
Review days when production, washing, cleaning and cooling discharge overlap.
Use water and deduction records from the same selected day.
Are domestic and indirect cooling water always deducted?
Water from these uses that enters pollution-prevention treatment is included.
Record the total use and its treatment return separately, then deduct only the difference.
Verify pipes, meters and deduction evidence rather than assuming a different destination.
Should I subtract internal reused water again?
This tool excludes internal piped reuse from fresh supply W at the outset.
R is a reference ledger quantity and does not reduce Q again.
If the process-reuse pipe or its exclusion from the fresh-water ledger is unverified, the result remains pending.
What happens at exactly 50 or 200 m³/day?
Exactly 50 m³/day belongs to class 4; exactly 200 belongs to class 3.
Exactly 700 and 2,000 belong to classes 2 and 1 respectively.
Classification precedes display rounding, and increasing by the stated boundary distance reaches the next class.
Does zero discharge mean no filing is needed?
A zero calculated quantity does not establish exemption from facility rules or approval as a zero-discharge installation.
Reference class 5 is shown only after ordinary wastewater-facility scope is confirmed.
Hazardous substances, site restrictions, facility type and installation/change procedures require separate review.
Does capacity above Q mean expansion is unnecessary?
The result is only a difference between the entered daily capacity and calculated daily discharge.
It does not assess instantaneous flow, concentration, retention time, operating hours, separate treatment trains or design reserve.
A positive margin does not establish design suitability or permit approval.
Can I save a pending result?
Yes.
TXT retains input quantities, confirmations, pending reasons and official sources.
Unknown values do not become zero or class 5.
Use the ledger to ask the authority or provider which meter records and deduction evidence need improvement, then recalculate.
Official sources, dates and your next action
Checked through the National Law Information OPEN API on 2026-11-04, Enforcement Decree MST284747 is effective 2026-03-24.
The worksheet follows Annex 13 and Notes 1–3 for the maximum-discharge day, supply-and-deduction formula, reuse exclusion, treatment inflow inclusion and first-installation plans.
The annex title retains a reference to Article 44(2), while the current Article 44 text concerns discharge-charge calculations; this page cites Annex 13 itself without treating that article text as a class formula.
Recheck the law after amendments and the ledger whenever processes or pipes change.
Prepare the peak-day records and whole-site expansion plan, confirm classification and installation/change procedures with the competent environmental authority, then compare revised quotations on the same treatment scope.