If you’re planning a low pressure misting system for polyhouse, water consumption is usually the first practical concern—especially when the system runs automatically on fixed timer cycles and temperature/RH triggers. The good news is: water use is easy to calculate and easy to control once you know your nozzle flow rate and total ON time.
This guide shows the exact method to estimate daily and monthly usage for a polyhouse misting system low pressure (and how to reduce water use without losing results).
Quick Answer (Use This Formula)
Daily water use (L/day) = Total system flow (L/min) × Total ON minutes per day
Where:
Total system flow (L/min) = Flow per nozzle (L/min) × Number of nozzles running
If you run multiple zones at different times, calculate each zone separately and add them.
What You Need Before You Calculate
Collect these 4 items (no guessing):
- Nozzle flow rate (L/min) at your working pressure
→ Get it from the nozzle chart/datasheet. - Nozzle count running at the same time
→ Count per zone/section. - Controller schedule
- Total hours the system is “enabled” (e.g., 11am–5pm)
- ON/OFF cycle timing (e.g., 15 sec ON / 90 sec OFF)
- Number of zones and whether they run together or separately
Step-by-Step Water Use Calculation
Step 1: Calculate total flow
Total flow (L/min) = Nozzle flow (L/min) × Nozzles running
Step 2: Convert your timer cycles into ON minutes per day
If your system is automatic and runs in pulses:
Duty fraction = ON time ÷ (ON time + OFF time)
Total ON minutes/day = Enabled minutes/day × Duty fraction
Step 3: Calculate daily water
Daily water (L/day) = Total flow (L/min) × Total ON minutes/day
Example 1 (Pulsed Auto System)
(Use your real nozzle flow—this example is only to show the method.)
- Nozzle flow: 0.20 L/min
- Nozzles running: 50
- Enabled time: 6 hours/day = 360 minutes
- Cycle: 15 sec ON / 90 sec OFF
- Duty fraction = 15 ÷ (15+90) = 15/105 = 0.143
- ON minutes/day = 360 × 0.143 = 51.5 minutes
Total flow = 0.20 × 50 = 10 L/min
Daily water = 10 × 51.5 = 515 L/day
How to Reduce Water Use Without Reducing Performance
These changes usually lower consumption while keeping results strong:
- Use shorter ON bursts + longer OFF gaps (biggest impact)
- Run only required zones (don’t cool the whole structure if only some bays need it)
- Add RH limit/lockout so the system pauses when humidity is already high
- Fix leaks and post-shutoff dripping (small drips add up daily)
- Maintain filtration so nozzles don’t “stream” or over-flow
- Keep mist positioned to condition the air, not directly soak plants—important for any mist system for polyhouse plants
FAQs (People Also Ask)
How much water does a low pressure misting system for polyhouse use per day?
Use: Daily water (L/day) = (nozzle flow × nozzle count) × ON minutes/day. This gives a reliable estimate.
Does automation increase water use?
Not when configured well. Automatic controls often reduce waste by running only when temperature demands it and stopping at high humidity.
Can I calculate water use for a misting system for greenhouse polyhouse setups the same way?
Yes. A greenhouse low pressure misting system uses the same calculation because flow and ON time still determine consumption.