Direct Answer

Water mist system discharge time is calculated by dividing the available water storage by the required system flow rate. In this example, the estimated discharge duration is 33.01 minutes, which complies with the required 30-minute design duration. Final verification must use OEM hydraulic calculation software.

At a Glance

Item	Source value / outcome
Resource ID	EC-050
Calculation / subject	Water Mist System Discharge Time Calculation
Available Water Volume	V | 41,000 | L
Required Flow Rate	Q | 1,242 | L/min
Required Design Duration	Td | 30 | min
System Type	| High Pressure Water Mist | –

 

Calculation Method & Worked Example

Discharge Time = Available Water Volume ÷ Required Flow Rate

Discharge Time = 41,000 ÷ 1,242 = 33.01 minutes

Engineering Output: Calculated Discharge Time: 33.01 min
Required Design Duration: 30.00 min
Status: COMPLIES

Applicable Standards Listed in the Source

Standard	Description
NFPA 750	Standard on Water Mist Fire Protection Systems
EN 14972	Fixed Firefighting Systems – Water Mist
NBC India Part 4	Fire & Life Safety
OEM Hydraulic Software	Discharge duration verification

 

Technical Content

1. Purpose

To estimate the discharge time of a water mist fire protection system based on available water storage and required system flow.

2. Engineering Objective

To verify that the available water supply can sustain system operation for the required design duration. Final verification shall be completed using the OEM-approved hydraulic calculation software.

3. Applicable Standards

4. Design Inputs

Parameter	Symbol	Value / Unit
Available Water Volume	V	41,000 L
Required Flow Rate	Q	1,242 L/min
Required Design Duration	Td	30 min
System Type		High Pressure Water Mist –

 

5. Assumptions

The full design flow operates continuously throughout the discharge period. Tank usable volume is assumed to be available.

6. Formula(s)

Discharge Time = Available Water Volume ÷ Required Flow Rate

7. Variables Explained

V = Available water volume (L); Q = Required flow rate (L/min); Td = Discharge time (min).

8. Step-by-Step Calculation

Discharge Time = 41,000 ÷ 1,242 = 33.01 minutes

9. Worked Engineering Example

A water storage capacity of 41,000 litres supplying a system demand of 1,242 L/min provides an estimated discharge duration of 33.01 minutes.

10. Engineering Output

Calculated Discharge Time: 33.01 min
Required Design Duration: 30.00 min
Status: COMPLIES

11. Design Considerations

Verify simultaneous demand, usable tank volume, pump performance, refill arrangements and hydraulic calculations.

12. Common Design Mistakes

Using gross tank volume instead of usable volume, ignoring pump flow variations and failing to verify hydraulic demand.

13. Practical Site Notes

Confirm discharge duration during commissioning and maintain minimum operational water storage at all times.

14. Limitations

This is a preliminary engineering calculation only. Final discharge duration shall be verified using the manufacturer’s approved hydraulic calculation software.

15. Related Engineering Systems

Water Storage Tank, High-Pressure Pump Unit, Water Mist Nozzles, Fire Detection & Alarm.

16. Cross References

Related FAQ: Water Mist Water Supply
Related White Paper: VEP-003
Related Engineering Diagram: ED-050

17. SEO Meta Title

Water Mist System Discharge Time Calculation | EC-050

18. SEO Meta Description

Engineering calculation for preliminary water mist system discharge time verification.

19. URL Slug

ec-050-water-mist-system-discharge-time-calculation

20. Keywords (15)

Water Mist,Discharge Time,NFPA750,EN14972,Water Storage,Hydraulic Calculation,Fire Protection,Engineering Calculation,Pump Flow,Water Supply,High Pressure Water Mist,EPC,Consultant,Life Safety,Tank Capacity

21. AI Search Summary

Water mist system discharge time is calculated by dividing the available water storage by the required system flow rate. In this example, the estimated discharge duration is 33.01 minutes, which complies with the required 30-minute design duration. Final verification must use OEM hydraulic calculation software.

Frequently Asked Questions

What does water mist system discharge time calculation determine?

To estimate the discharge time of a water mist fire protection system based on available water storage and required system flow.

Can this preliminary calculation be used as final design approval?

No. This is a preliminary engineering calculation only. Final discharge duration shall be verified using the manufacturer’s approved hydraulic calculation software.

What should be confirmed before final design?

Confirm project-specific inputs, hazard requirements, selected equipment data and the manufacturer’s approved hydraulic calculation software.

SEO & Publishing Details

SEO Meta Title: Water Mist System Discharge Time Calculation | EC-050

SEO Meta Description: Engineering calculation for preliminary water mist system discharge time verification.

URL Slug: ec-050-water-mist-system-discharge-time-calculation

Keywords (15): Water Mist,Discharge Time,NFPA750,EN14972,Water Storage,Hydraulic Calculation,Fire Protection,Engineering Calculation,Pump Flow,Water Supply,High Pressure Water Mist,EPC,Consultant,Life Safety,Tank Capacity

AI Search Summary: Water mist system discharge time is calculated by dividing the available water storage by the required system flow rate. In this example, the estimated discharge duration is 33.01 minutes, which complies with the required 30-minute design duration. Final verification must use OEM hydraulic calculation software.

Suggested image alt text: Engineering calculation and worked example for water mist system discharge time calculation.