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Dechlorination
v1.1

Tank

Getting started

New to this tool? Turn on Worked example (top right) to see a tank and a pipeline worked through, then turn it off to enter your own. Your own entries come back when it is off.

Use this for a fixed volume of chlorinated water in a tank, reservoir or basin. Two common jobs:

  • Pre-discharge: neutralise chlorine before releasing water to the environment or a stormwater system.
  • Overdose correction: pull a chlorine overdose back down to a target residual before returning the tank to service.

Enter the tank volume, the measured chlorine residual and your target. Pick an agent and how you will dose it. The tool returns the quantity to add, the environmental impact of any excess, and mixing and verification guidance.

The tool does the maths — you enter what you can measure on site. The Pipe tab does the same for a pipeline, as a batch or as continuous injection into a flush.

Clear all (bottom of this tab) empties both tabs; Settings are kept.

Water volume

Use dimensions if you only know the tank size and water depth.
m³
Volume of water to treat, at the current level

Chlorine

mg/L
Expressed as Cl₂
What the test measured. Combined chlorine needs longer contact
mg/L
Use 0 for discharge; use your service residual for overdose correction
pH impact — optional

Enter what you know. With starting pH and alkalinity the tool predicts the pH after dosing. Temperature refines the estimate and the contact-time guidance.

Measured before dosing, typically 6.5 to 8.5
mg/L
as CaCO₃
°C
Typically 5 to 25 °C; leave blank if unknown

Dechlorinating agent

The chemical you will dose. Ascorbates do not strip dissolved oxygen
A made-up solution, or the dry product as supplied
g/L
Grams of agent per litre of made-up solution
%
A small excess guarantees zero residual; large excess wastes chemical and loads the environment
L/s
If you can recirculate, the tool estimates a mixing turnover time

Colour bands are prompts to look, not instructions to act.

Pipe

Guide: using this tab

Use this for chlorinated water in a pipeline. Two common jobs:

  • Emptying a line: a main carrying normal service water that must be drained down.
  • Commissioning a new main: a line that was superchlorinated for disinfection (often 25–50 mg/L held for a period) and must be dechlorinated before the flush water is discharged.

Batch mode treats the standing volume in the line. Continuous injection mode gives a dosing rate for feeding agent into a flush stream at the discharge point.

Chlorine is acutely toxic to aquatic life at very low concentrations, so superchlorinated flush water must never reach a waterway untreated.

Job type

Batch treats the water standing in the line; continuous sizes an injection rate into a flush.

Pipe geometry

mm
Bore, not nominal size
m
Length of line being drained or flushed

Chlorine

mg/L
Expressed as Cl₂
What the test measured. Combined chlorine needs longer contact
mg/L
Use 0 for discharge
pH impact — optional

Enter what you know. With starting pH and alkalinity the tool predicts the pH after dosing. Temperature refines the estimate and the contact-time guidance.

Measured before dosing, typically 6.5 to 8.5
mg/L
as CaCO₃
°C
Typically 5 to 25 °C; leave blank if unknown

Flush flow

L/s
Used to set the agent injection rate

Dechlorinating agent

The chemical you will dose. Ascorbates do not strip dissolved oxygen
A made-up solution, or the dry product as supplied
g/L
Grams of agent per litre of made-up solution
%
A small excess, typically 5 to 20%, guarantees zero residual

Colour bands are prompts to look, not instructions to act.