Water treatment calculators
A calculator and model suite, aligned to NZ and/or global standards. Opmate, our AI operator assistant, is launching soon — join the waitlist below.
The full toolkit for plant operators and designers
Every calculator produces estimates based on real operations and design experience. However, the outputs do not constitute engineering, regulatory, scientific, legal, or other professional advice, and are not a substitute for the judgement of a suitably qualified and experienced professional who has assessed your specific circumstances.
Water Chemistry Model
pH, alkalinity,LSI, CCPP, corrosion indices, plant sizing and dosing costs.
Chlorine Demand & DBP Model
Model chlorine residual decay and disinfection by-product formation.
DWQAR Sample Scheduler
Smart sample schedule generator for all supply types for new 2027 DWQAR rules.
Filter Monitoring Tool
Monitor long term performance of filters. Backwash profiles, media depths and dirt content.
Jar Testing Tool
Set up mixing, make solutions, determine dosing regimen and assess results.
Operator Maths Tool
All the maths functions and calcs that operators need to know and use.
Arsenic Tool
Determine arsenic type and assess treatment options for removing.
Nitrate Tool
Determine nitrate/nitrite risk and assess treatment options for removing.
Pump System Calculator
Pump curves, system curves, VSD modelling, costs and surge analysis.
Plant Hydraulic Model
Determine the hydraulic grade line for gravity flow plants for a range of flowrates.
Tank Sizer
Size tanks & wet wells for continuous and batch operations.
Operator Staffing Tool
Work out how many operators you need, or assess risk of your current levels.
Plant Mass Balance Tool
Full plant mass and flow balance for a range of scenarios, including residuals management.
Plant Audit Model
Structured audit framework to assess and benchmark plants.
Oxidation Tool
Determine the optimum process for oxidation of Fe, Mn & ammonia.
Compliance Indices Tool
Determine compliance and assurance indices for suppliers, supplies, plants and zones.
Dechlorination Tool
Determine dechlorination requirements and impacts for tanks and pipelines.
PID Tuning Tool
Tune water treatment control loops - flow, level, pressure and feedback dose control.
Critical Control Point Tool
Develop your CCP register and responses based on DWQAR and best practice.
DWQAR Assurance Rule Tool
Develop your assurance and reporting rules strategy and response.
PAC Dosing Tool
Determine PAC dose required for removal of organics contaminants.
Treatment Process Selector
Recommend treatment process trains based on raw water quality and DWQAR.
Filter Design Tool
Size rapid gravity filters including media, backwash & internals.
MF/UF Membrane Design Tool
Size and manage MF/UF membrane plants including configuration, LRV and repairs.
UV Design Tool
Size and model UV plants for disinfection and advanced oxidation.
Chlorination Design Tool
Size and model chlorine gas and hypo storage, dosing and contact tanks.
Multi-Criteria Analysis Tool
Make transparent decisions. Set-up, score and assess decision sensitivity.
Cost Esimating Tool
Create capex, opex and NPVs for multiple options, with multiple contingency models
Carbon Footprint Tool
Create an operational carbon inventory for a drinking water supply, from the source to the tap.
New Source Sampling Tool
Determine the optimum sampling regime for any new source type.
If you have any requests for new tools, want any changes, or spot any bugs we'd love to hear from you.
Meet Opmate — the AI assistant that does the job alongside you.
Calculators give you numbers. Opmate gives you answers. Built on 25+ years of plant operating experience, Opmate troubleshoots issues, runs the calculators for you, and grounds every recommendation in your plant's own documents.
- Diagnoses plant issues conversationally
- Picks the right calculator and runs it for you
- Reads your Ops Manual, WSP, SOPs, and SRMP
- Available on desktop or mobile, on shift
Steps we need to take:
1. Check the poly dose setpoint. For stable conditions it should be around 0.05mg/L.
2. Do a dose time to confirm if the dose pump is delivering this.
3. Check the batching system. We may have made up a batch that is too strong.
Built for operators and engineers
Free to use
Every calculator's basic tabs are free, forever. Premium unlocks advanced tabs.
Expert built
25+ years of operational experience encoded into every formula, default, and assumption.
Mobile ready
Designed for the way operators actually work — on shift, in the field, on a phone.
NZ & global
Tools for both Taumata Arowai / DWSNZ and global standards. Filter by region.
Free to use, Premium to unlock more
Every calculator is free. Most also include advanced features that only unlock with Premium. Any applicable tax is added at checkout.
Premium
Access to advanced calculator features.
- Advanced calculator functions
- Save & import
- PDF & CSV export
Need multiple seats for your team or organisation? See team pricing — from 3 seats, pay by card or invoice.