Urinal Flush Calculator

Calculator inputs

Example data table

Formula used

• Total flushes per day = Urinals × Flushes/urinal/day × Occupancy factor
• Daily water use (L) = Total flushes per day × Flush volume (L)
• Daily water use (m³) = Daily liters ÷ 1000
• Annual water use (m³) = Daily m³ × Operating days/year
• Annual cost = Annual m³ × Water rate per m³
• Peak-hour flushes = Urinals × Peak flushes/hour/urinal × Occupancy factor
• Avg peak-hour flow (L/s) = (Peak-hour flushes × Flush volume L) ÷ 3600
• Burst flow (L/s) = (Urinals × Flush volume L) ÷ Flush duration seconds

Fixture demand and usage profiling

Reliable sizing starts with a realistic fixture count and a defendable usage estimate. Use observed occupancy, shift patterns, and event peaks to set flushes per urinal per day. Apply an occupancy factor to represent seasonal surges or partial building fit‑out. This approach keeps the daily total aligned with how the space is actually operated, not just theoretical maximums. Record assumptions. Support reviews.

Converting flush ratings into volume totals

Each valve rating becomes a water volume when multiplied by expected flushes. Enter the flush volume in liters or gallons, then the calculator converts to liters. Daily liters are converted to cubic meters for monthly and annual reporting. This makes it easy to compare valve settings, sensor delays, or low‑volume upgrades on the same basis.

Peak flow checks for branch sizing

Plumbing coordination often needs a peak perspective, not only annual totals. The peak flushes per hour input estimates a representative busy hour for each urinal. The calculator reports an average peak‑hour flow rate in liters per second for coordination. A conservative burst flow check assumes all urinals flush within the chosen duration, highlighting worst‑case transients. Use it during concept design.

Cost modeling and retrofit comparison

Water cost is modeled from annual cubic meters multiplied by the local rate per cubic meter. If you include sewer or blended tariffs, the estimate better reflects real billing. The baseline comparison option supports retrofit decisions by quantifying annual volume and cost differences between an older valve and a proposed low‑volume or optimized control setting, under the same occupancy assumptions. Validate savings. Confirm with metered results after commissioning.

Reporting, commissioning, and operations

Use the CSV and PDF outputs to support design reports, value engineering, and commissioning submittals. Record the assumptions beside calculated results so stakeholders understand the basis of estimate. During operation, update inputs after occupancy changes or tenant turnover to keep budgets accurate. Combining totals with peak indicators helps align conservation with reliable service pressure.

FAQs

How do I estimate flushes per urinal per day?

Start with occupant counts, shift length, and break patterns. Multiply expected users by visits per user, then divide by urinals. Adjust with the occupancy factor for seasonal peaks or partial occupancy.

Should I enter liters or gallons?

Choose the unit that matches your fixture rating. If you select gallons, the calculator converts to liters internally and reports totals in cubic meters for consistent reporting.

What does occupancy factor mean?

It scales all usage to reflect real conditions. Use 1.0 for typical operation, less than 1.0 for low occupancy, or greater than 1.0 for special events and surge periods.

How are peak flows used in design?

Peak-hour flow supports coordination for pipe sizing and supply capacity. Burst flow is a conservative check for near-simultaneous flushes and can highlight potential pressure drops or transient concerns.

How does the baseline comparison work?

Enable baseline, enter the older flush volume and flush frequency, and the tool calculates annual water and cost differences. Use the same occupancy factor and operating days for an apples-to-apples retrofit estimate.

Can I use the downloads for submittals?

Yes. The CSV is useful for spreadsheets and audits, while the PDF summarizes assumptions and results for reports. Re-run calculations whenever occupancy, tariff rates, or valve settings change.