| Scenario | Volume | Target | Concentrate | Result (conc + water) |
|---|---|---|---|---|
| Pond loop, mild frost | 60 L | 30% | 95% | 18.95 L + 41.05 L |
| Irrigation manifold | 25 gal | 35% | 100% | 8.75 gal + 16.25 gal |
| Greenhouse coil | 0.12 m³ | 45% | 95% | 0.057 m³ + 0.063 m³ |
| Already has premix | 100 L | 35% | 95% | Depends on existing percentage |
TargetGlycol = SystemVolume × (Target% ÷ 100)ExistingGlycol = SystemVolume × (Existing% ÷ 100)ConcentrateNeeded = (TargetGlycol − ExistingGlycol) ÷ (Concentrate% ÷ 100)WaterNeeded = SystemVolume − ConcentrateNeeded- Enter your system volume and choose a unit.
- Select propylene glycol for safer garden use.
- Choose auto temperature mode or manual percentage.
- Set concentrate strength from the product label.
- Optional: enter existing premix percentage, if any.
- Click Calculate, then export CSV or PDF reports.
- If the system is already full, drain an equal volume before adding concentrate.
- Never pour toxic antifreeze onto soil or drains.
- Confirm freeze protection targets from your product datasheet.
Target percentages by temperature
For planning, many growers aim for 20% glycol near 0°C, 30% near -4°C, 35% near -7°C, and 45% near -12°C. Auto mode converts your protection temperature to a typical target percent, then calculates the glycol volume required for the full system. Ethylene mixtures can reach similar protection with slightly lower percentages, but they carry higher handling risk around beds, pets, and drains.
Concentrate strength and product labels
Concentrate is rarely exactly 100%. RV and marine propylene glycol is commonly 95–100%, while many store premixes are 50%. This calculator uses your entered concentrate strength to convert “pure glycol needed” into a real pour volume you can measure with a jug. If you are using a premix as the source fluid, set concentrate strength to that premix percentage.
Existing fluid and top‑up strategy
If your loop already contains antifreeze, enter the current percentage to avoid overdosing. The tool estimates existing glycol volume, subtracts it from the target glycol volume, and only adds the shortfall. When the system is full, drain the same volume you plan to add so total capacity stays constant. For drip lines, purge water first to reduce dilution errors.
Why volume matters in garden systems
Ponds, drip manifolds, greenhouse coils, and water features have narrow passages that freeze first. A correctly sized mixture reduces ice expansion stress, lowers the chance of cracked fittings, and helps pumps restart reliably after long cold nights. It also protects check valves, emitters, and filter housings that are expensive to replace mid‑season.
Operational checks before winter
After mixing, circulate the loop to blend thoroughly, then recheck levels at a consistent temperature. Inspect hoses, clamps, and unions for seepage, and label the fill point with the target percentage and date. Record batch volume for future refills. Keep spill absorbent nearby, store containers sealed, and dispose responsibly at season end. Flush with clean water before spring irrigation and confirm plants are not exposed to runoff.
1) Which antifreeze is safer for gardens?
Propylene glycol is generally preferred around plants and pets. Ethylene glycol is toxic and can contaminate soil and water if spilled. Always follow label safety instructions and local disposal rules.
2) Why does the calculator ask for concentrate strength?
Because the pour volume depends on how strong the concentrate is. A 95% product requires more volume than a 100% product to supply the same pure glycol amount.
3) What if my system is already full of water?
Drain an amount equal to the concentrate you plan to add. This keeps the system at its designed capacity and avoids overflow while still reaching the calculated target percentage.
4) How do I estimate existing premix percentage?
Use a refractometer or hydrometer that matches your fluid type and read at a stable temperature. If you are unsure, set existing percentage to zero and confirm with testing after mixing.
5) Does auto mode guarantee freeze protection?
No. Auto mode uses typical planning values. Real performance depends on product formulation, concentration accuracy, and system conditions. Verify your target with the product datasheet or measured testing.
6) Can I export multiple calculations?
Yes. Check “Save this calculation” before calculating to add it to the session log. Then download a CSV or PDF report containing your saved entries.