Calculator
How to use this calculator
- Measure your water volume in liters, gallons, or cubic meters.
- Test current free chlorine using a reliable kit or strips.
- Pick a target ppm suitable for your garden task.
- Estimate demand based on water clarity and organic load.
- Select your chlorine product and its strength percentage.
- Calculate, dose, mix well, wait, then re-test.
Formula used
This calculator treats ppm as mg/L.
- Total ppm increase = (Target − Current) + Demand
- Adjusted ppm = Total ppm increase × Adjustment factor
- Available chlorine needed (mg) = Adjusted ppm × Volume(L)
- Available chlorine needed (g) = mg ÷ 1000
- Product mass (g) = Available chlorine (g) ÷ (Strength% ÷ 100)
- Liquid volume (mL) = Product mass (g) ÷ Density (g/mL)
Example data
| Scenario | Volume | Current | Target | Demand | Product | Strength |
|---|---|---|---|---|---|---|
| Clean rinse bucket for tools | 20 L | 0.0 ppm | 2.0 ppm | 1.0 ppm | Liquid bleach | 10% |
| Drip line flush mix | 200 L | 0.2 ppm | 3.0 ppm | 2.0 ppm | Cal-hypo | 65% |
| Storage tank maintenance dose | 1 m³ | 0.5 ppm | 2.5 ppm | 1.5 ppm | Liquid bleach | 12.5% |
What chlorine demand means in garden water
Chlorine demand is the portion of added chlorine that is consumed before a stable free chlorine reading appears. In garden setups, demand rises when water carries algae, soil fines, leaf tannins, or biofilm from hoses and tanks. Measuring demand helps you avoid under-dosing, which leaves microbes active, and over-dosing, which can stress sensitive plants.
Inputs that change demand the most
Volume sets the total mass of chlorine required, while the gap between current and target sets the baseline increase. Demand represents immediate consumption from organics and reducing agents. The adjustment factor lets you account for real-world loss from sunlight, imperfect mixing, and aged product strength.
Choosing a practical target level
Targets should match your purpose. For tool-rinse buckets and line flushing, moderate free chlorine can help control microbial growth during contact time. For irrigation water that reaches plants, keep targets conservative and verify crop tolerance. Always re-test after mixing and allow time for demand to settle before deciding on a second dose.
How product strength affects dosing
The calculator converts your required available chlorine into a product dose using the strength percentage. Stronger products require less material, but they can degrade faster in storage. For liquids, density converts grams to milliliters for easier measuring. For granular products, dosing is shown in grams and kilograms to scale from small batches to tanks.
Good testing and dosing workflow
Start by cleaning debris screens and draining stagnant sections. Mix chlorine into circulating water, then wait a short contact period and test again. If free chlorine is below target, add a partial top-up rather than repeating the full dose. Keep notes for your water source and season, because demand often changes after rain, heat, or tank cleaning.
If you are troubleshooting persistent demand, inspect for biofilm inside tanks, filters, and emitters. Mechanical cleaning often lowers demand more than repeated dosing. Maintain consistent measurement units, use clean sampling containers, and store test reagents correctly to keep readings dependable.
FAQs
1) Why is my demand higher after rain?
Runoff can add organic matter, soil particles, and microbes that consume chlorine immediately. Expect higher demand, dose in smaller steps, mix well, and confirm results with a fresh test.
2) Can I use this for drip irrigation tanks?
Yes, but keep targets conservative and confirm plant tolerance. Dose, circulate, and re-test after contact time. If water goes directly to crops, avoid excessive residual chlorine.
3) What if my current value is already above target?
The calculator will reduce the required increase to zero unless you add demand. If levels are high, dilute with clean water, allow time to dissipate, and re-test before irrigating.
4) Does sunlight change the result?
Sunlight breaks down free chlorine, especially in open containers. Use shaded mixing when possible, cover tanks, and consider a small adjustment factor increase if losses are consistent.
5) Which strength value should I enter?
Use the label’s available chlorine percentage. If the product is old or stored warm, effective strength may be lower. When unsure, use a modest adjustment factor and validate with testing.
6) How soon should I re-test after dosing?
Re-test after thorough mixing and a short contact period, often 10–30 minutes depending on volume and circulation. Then fine-tune with a smaller top-up if needed.