Garden Irrigation Zones, Water Use and Cost Calculator

Plan separate irrigation zones from device flow and supply capacity. Check sequential runtime, monthly water use and operating costs with your KRW rates.

Turn device flow and schedules into zones and a monthly budget.

Use one group for identical devices, flow and schedules. Groups stay separate and zones run one at a time. Flow uses L/min or L/h; all prices use KRW.

Source check: 2026-09-11 · User-supplied tariffs and watering schedules

1. Supply capacity and shared calendar

An unrestricted tap-flow test does not establish end pressure. Use capacity at the required operating pressure after other water use. Avoid deducting reserve twice. Exclude skipped rainy days from the month.

2. Groups of identical devices

Separate drip emitters, sprinklers and areas with different exposure or schedules. Add up to six groups. A zero device count excludes that group.

Group 1

3. Actual rates, pump power and upkeep

Use electrical input power, not motor shaft output. The model assumes constant power for all zones. Water/sewer tiers, base fees, taxes and discounts are not automatic; include applicable costs once in your rates or upkeep.

Flow unverified · provisional planPressure and pipe suitability require site verification.

★ Minimum zones, groups separate

0

Flow-only lower bound: 0

Planned water / month

0 m³

0 L/irrigation day

Sequential runtime / watering day

0 min

Window: 120 min

Monthly operating cost

Check prices / capacity

Water + power + fixed upkeep

Flow, volume and cost breakdown

Usable / total connected flow
0 / 0 L/min
Each group once, combined
0 L
Monthly pump hours / energy
0 h / 0 kWh
Monthly water cost (planned)
Check prices / capacity
Monthly electricity cost
Check prices / capacity
Fixed monthly upkeep
Prices unverified

Balanced zones within each group

Zone numbers restart within each group. Identical zones share a range; monthly volume totals all zones in that row. More zones do not increase water use when each device runs for the same time.

Group zone allocation, devices, flow, schedule and monthly water
Group / zonesDevices/zoneL/minSpare L/minMin/cycleCycles/dayRow total m³/month
Group 1No devices

Switching and soak delays, pipe friction, elevation, actual rain, soil moisture and tiered tariffs are outside the model. Share this plan with the installer alongside device flow and pressure data.

Related calculators

Plan irrigation zones before ordering parts

This garden irrigation calculator connects available supply flow, individual devices and watering schedules to a zone plan and monthly operating budget.

Check simultaneous demand

The number of devices you can connect is different from the number your supply can operate together.
Demand above available flow can leave the far end of a garden short of water.
The minimum zone count applies to the entered flow constraints with groups kept separate; it is not a final hydraulic design.

Connect water volume to costs

Small emitters can still use substantial water when there are many devices or long runtimes.
Compare drip emitters and sprinklers in consistent units, then include your water price, electrical pump input and upkeep.
The plan is suitable for discussing a garden, vegetable plot or flower bed with an installer.
The English version uses SI units and KRW prices, with the same formulas as the Korean version.

What the inputs mean

Read the flow unit and the pressure conditions on the device performance sheet before entering a value.

Supply and additional reserve

Supply flow means litres per minute available at the operating pressure the irrigation equipment needs.
An unrestricted hose or bucket test does not establish pressure at a working emitter.
Account for other household water use, then enter only the additional reserve you want to leave unused.
The initial reserve is 0%; avoid deducting the same allowance twice if an installer already included it.

Device groups and schedules

A group contains devices with the same type, individual flow, runtime per zone and daily cycle count.
Keep drip emitters and sprinklers in different groups rather than entering an average flow.
Separate locations with different sunlight, plants or watering needs; devices from different groups are never combined in this model.
Irrigation days are the days this month when all entered groups will operate; subtract skipped rainy days yourself.

Pump and price evidence

Pump power means electrical input during operation, not mechanical shaft output.
Enter 0 if you do not use a pump; otherwise use a measurement or a specification appropriate to the operating conditions.
Water price is the incremental volumetric rate for the additional irrigation water.
Use your electricity rate and fixed upkeep, and record the device, working pressure, tariff band and checked date in the source note.

Zone formulas: a flow lower bound and whole-device allocation

Let C be available flow after the additional reserve, q the individual device flow in L/min, and n the device count.

Convert units and find a lower bound

Divide flow stated in L/h by 60 to obtain L/min.
Usable flow is C = supply × (1 − reserve/100), and total connected flow is F = Σ(n × q).
The reference lower bound is ceil(F/C), where ceil means round up.
It ignores whole-device and group constraints, so it is not a valve shopping list.

Respect indivisible devices

The maximum devices per zone is k = floor(C/q), where floor means round down.
For each group, the minimum is z = ceil(n/k); add the group counts to obtain the separated total.
With supply 10 L/min and three devices using 6 L/min each, the total-flow lower bound is 2, but only one device fits per zone, requiring 3 zones.
If even one device exceeds available flow, adding zones cannot fix it; the plan is marked unavailable.

Read the balanced allocation

Devices are spread as evenly as possible across the required zones, with counts differing by at most one.
At 10 L/min supply, twelve 2 L/min devices need 3 zones: four devices and 8 L/min per zone.
Identical zones are compressed into a range in the table, and zone numbering restarts within each group.
Monthly volume in a table row totals every zone in that range.

Water volume, sequential runtime and monthly costs

Only one zone operates at a time, and water volume must be summed differently from pump runtime.

Do not multiply water volume by zones twice

One group cycle uses n × q × minutes litres.
Multiply that by the group cycles per irrigation day, then by irrigation days and divide by 1000 to obtain monthly m³.
Add the groups for the total; “each group once” means one cycle of every group, regardless of their daily cycle counts.
Splitting zones leaves water volume unchanged if every device runs for the same time; the device count already includes all zones.

Runtime and energy

Daily sequential minutes = Σ(group zones × minutes per zone × cycles per day).
Monthly pump hours = daily minutes × irrigation days ÷ 60, and monthly kWh = hours × electrical input kW.
The calculator flags a daily window overrun but excludes valve switching and soak delays.
Zero irrigation days, cycles or minutes reduce the relevant monthly operation and volume to zero, while installed zone counts remain visible.

Use your actual incremental costs

Monthly water cost = monthly m³ × water price; monthly electricity cost = monthly kWh × electricity price.
Total monthly operating cost adds water, electricity and fixed upkeep, which remains even in a month without watering.
Unconfirmed prices withhold cost results; an infeasible zone plan also withholds electricity and the combined cost.
Any separately shown water cost is a budget for the entered schedule demand, not evidence of achievable delivery.

How to use the calculator

The initial screen starts key quantities and prices at zero instead of assuming your water use or tariff.

Step 1 · Supply and calendar

Enter capacity at working pressure from the installer or your measurement record and an additional reserve that does not duplicate an existing allowance.
Set the daily operating window and irrigation days this month.
Leave flow confirmation unchecked when the input is still provisional.

Step 2 · Groups and runtime

Group identical equipment and select the correct unit for one device.
Enter the device count, minutes per zone per cycle, and cycles on a watering day; add up to six groups.
Use zero devices for a group you have not installed, which removes its zones and water from the calculation.

Step 3 · Budget and export

Check the scope of your water price, electricity price, pump power and upkeep, then confirm the prices.
Review zones, daily window, monthly water and cost in that order before exporting a CSV with your source notes.
The fictional example sets hypothetical confirmation boxes too; replace those assumptions with actual device and rate information.

Worked example: a lower bound of 4 but 6 separated zones

These are fictional arithmetic inputs, not recommended equipment settings or average market prices.

Assumed inputs

Supply is 10 L/min, additional reserve 0%, irrigation days 20, and the daily window 120 minutes.
Group A has fifty 6 L/h devices, running for 30 minutes per zone twice a day.
Group B has five 6 L/min devices, running for 10 minutes per zone once a day.
Assume pump input 0.5 kW, water 1,000 KRW/m³, electricity 200 KRW/kWh and fixed upkeep 3,000 KRW.

Zones and water

Group A uses 5 L/min and needs 1 zone; group B needs 5 zones with one device each, giving 6 zones in total.
Total connected flow is 35 L/min, so dividing by supply 10 gives a lower bound of 4; whole devices and separate groups explain the difference.
One cycle uses 150 L for A and 300 L for B, or 450 L combined.
On an irrigation day, A uses 300 L and B uses 300 L, totalling 600 L; over 20 days, monthly use is 12 m³.

Time and cost

A runs for 60 minutes a day and B for 50, totalling 110 minutes within the 120-minute window.
Monthly pump operation is about 36.67 hours and energy about 18.33 kWh.
Water costs 12,000 KRW, electricity about 3,667 KRW and fixed upkeep 3,000 KRW, giving about 18,667 KRW per month.
Calculations retain full precision and round only for display; multiplying the displayed rounded energy can produce a small currency difference.

Use cases: ordering parts, adjusting schedules and budgeting

Keep comparable inputs unchanged when examining the effect of one planned change.

Before ordering equipment

Compare the existing and expanded device count for zones, spare flow per zone and sequential runtime.
Ask the installer about spare controller stations, valve specifications, placement and wiring before purchasing from a calculated zone count.
For dripline sold by length, determine the number of individual outlets from the product spacing and enter that outlet count.

When the day is too short

More zones can reduce simultaneous flow while increasing sequential runtime.
The daily window assumes all groups run on the same watering days; compare a different-day arrangement as a separate scenario.
Do not shorten watering solely to make the time total fit without checking plant water requirements.

Monthly budget and maintenance

In a wetter month, reduce the confirmed watering days and compare the plan with your water meter.
Large differences warrant checking leaks and controller schedules.
Rainwater or well water may still require pump electricity, filters and maintenance, even with a zero mains-water price.
Tank capacity and monthly rainwater shortages belong in a separate storage water-balance calculation.

Limits and practical cautions

The zone table is an arithmetic plan for your entered counts and flow, not certification of even water distribution.

Site design still matters

Pipe length, diameter, elevation, clogged filters, regulators and end pressure are not simulated.
Individual discharge can depend on pressure; do not combine performance figures measured under incompatible conditions.
Device spacing, sprinkler overlap, soil infiltration and plant needs also require separate checks.
Checking the flow box records your input confirmation, not a software test of hydraulic performance.

Scheduling and energy limits

The model assumes one pump operates at the same electrical input whenever any zone runs.
Pump cycling in low-flow zones, variable-speed behaviour, switching delays and soak pauses are excluded.
Extreme schedules can exceed 24 hours; the overrun result is a signal to revise the plan, not an executable schedule.

Prices, local requirements and defaults

Water/sewer tiers, surcharges, base fees, taxes and discounts are not applied automatically.
Count included costs only once in the entered unit rates and upkeep; check the actual bill against local tariffs and meter intervals.
Software input limits are not recommended engineering ratings.
Installation permissions, backflow protection and other local conditions require the installer or relevant authority.

Frequently asked questions

Does adding zones increase my water bill?

Water volume stays the same when device counts and individual runtimes are unchanged.
Sequential pump operation can become longer, so electricity may change with the schedule.

What happens if I select the wrong flow unit?

L/h and L/min differ by a factor of 60.
Check whether the product figure is per hour or per minute and whether it covers one emitter or the entire line.

Can drip emitters and sprinklers share a calculated zone?

This model keeps groups separate.
It does not average different flow, timing or pressure needs; a mixed layout requires site design verification.

Can I add zones when one device exceeds supply?

A device cannot be split, so adding zones does not solve that constraint.
Check supply capacity or device specifications and do not treat planned demand as achievable water delivery.

Are rainy days and plant watering recommendations automatic?

The calculator does not fetch real-time rain or prescribe plant-specific schedules.
Enter the confirmed runtime and watering days yourself and compare different months separately.

Why is there a cost in a month with no irrigation?

The entered fixed upkeep remains when water and pump energy are zero.
Set that item to zero if it does not actually apply this month, and check the price confirmation.

What should I send to an installer?

Share the CSV zone table, site plan, device flow and pressure documents, and source check date.
Request review of end pressure, pipe losses, pump operation, group separation and the daily schedule.

Sources and future checks

Sources checked on 2026-09-11.
The model uses technical guidance available in 2026 and does not apply future tariffs or a statutory watering schedule.
Use your current product performance sheets and local incremental rates instead of past product values or prices.

Update the inputs and evidence note when product specifications, rates or supply conditions change.
Integer allocation, unit conversion and monthly cost formulas are the explicit model above, not a billing calculation or installation warranty.

Build your garden zone plan and budget

Enter individual device flow and available supply to review zones, sequential runtime and monthly volume.
Export the plan for a pressure and pipe review and a parts quote from your installer.

Return to the irrigation calculator