Setup
Getting started
New to this tool? Turn on Worked example (top right) to load a sample supply, then step through the tabs. Turn it off to go back to your own supply, which is kept aside meanwhile.
This tool encodes the Water Services (Drinking Water Quality Assurance) Rules 2026, in force from 1 July 2027. The 2026 Rules revoke and replace the DWQAR 2022. Compliance is assessed over the compliance year (1 July to 30 June), not the calendar year, and every schedule and calendar here runs on that basis. For sampling before 1 July 2027, work to the 2022 Rules.
To build your plan:
- Pick your supply category and population. This assigns the rule modules (rule 6).
- Add your sources and set each source water class. This one field drives the whole S3 monitoring load.
- Add treatment plants and tick the chemicals you dose (these trigger chemical and DBP monitoring).
- Add distribution zones with their populations. These set the D3 FAC and microbiological sampling tiers.
- Open Schedule for the annual sampling load, then Calendar for actual sample dates across the compliance year.
Three scenarios. The schedule and calendar run on the mandatory minimum by default: exactly what the Rules require. Two further scenarios (Premium) add headroom: compliance margin lifts distribution FAC one step so one low reading cannot fail the percentage rule, and lowest risk lifts FAC to the maximum and raises E. coli monitoring above the minimum to detect contamination sooner. FAC is the only determinand with a percentage-of-samples compliance rule; the extra E. coli sampling lowers supply risk rather than buying compliance tolerance. The Scenarios tab compares all three.
Lab unit prices are in Settings. Clear all (foot of this tab, two clicks) empties the supply; Settings are kept. About this model has the full basis, limitations, assumptions and public references.
The tool gives guidance only. Confirm your obligations against the gazetted Rules.
Source class drives the whole S3 monitoring load. Under rule 8, Class A and B need a sanitary bore head and 3 years of clean E. coli / total coliform history (12 samples a year) before they qualify; in return, protozoa treatment drops to 0-log and raw-water sampling is lighter. Class C and D (surface water and shallow or unprotected groundwater) carry the full continuous monitoring plus twice-monthly micro and the cyanobacteria regime. Class A also needs F-specific RNA bacteriophage monitoring (3 a year).
Periodic items and the 50% MAV follow-up. This is a plan for one compliance year, so multi-year items are a yes/no per source: tick those actually due this year (the 3-yearly source metals, the 10-yearly groundwater radiological, the periodic full DWSNZ chemical suite). Ticked items are scheduled once this year and costed in full. If a result comes back over 50% of its MAV, the Rules require ongoing monitoring of that determinand until three consecutive results sit at or below 50%: add it under Ongoing parameters flagged over 50% MAV, with a frequency. Anything not in that list can be named as a custom parameter in Settings, after which it can be picked here.
Treatment chemicals trigger T3.CH chemical monitoring. Under T3.CH.3, every dosed chemical that has a MAV (and any source determinand over its MAV) is monitored monthly in treated water, reducible to annual after 12 consecutive results at or below 50% MAV. Sodium hypochlorite brings weekly chlorate (T3.CH.4); chlorine dioxide brings weekly chlorite and chlorate (T3.CH.5). Fluoride, if dosed, is continuously monitored (T3.CH.6). Hypochlorite and HFA (fluorosilicic acid) vapour corrode plant-room metalwork; keep dose systems cabinet-housed.
D3.RD.4 and D3.MM.2 set spacing and weekend rules by zone population. FAC grab sampling (D3.RD.4) runs 12 to 24 samples a month with a maximum 2 to 4 day gap. Microbiological sampling (D3.MM.2) runs 4 to 12 samples a month and, above 25,000 people, needs a minimum number of Saturday and Sunday samples each compliance year. Continuous FAC analysers (D3.RD.6) replace the grab tiers with 2 to 4 analysers plus 4 confirmatory FAC and pH grabs a month (D3.RD.8).
One zone is one sampling line here, but the Rules need several sites per zone. The planner counts samples per zone, not sampling points. Your written sampling plan spreads them across representative locations: peripheral and central, plus higher-risk or high-density areas (D3.RD.5, D2.3). DBP sites alternate between peripheral and central (D3.RD.10); microbiological sites include storage exits and inter-supplier entry points (D3.MM.4). This changes where you sample, not how many samples or the cost.
The full 34-determinand set from the Aesthetic Values for Drinking Water Notice 2022, costed as one suite per sample point (set the rate in Settings).
Determinands in the suite
Schedule
Guide: using this tab
The annual sampling load from your supply setup, one line per determinand and rule. Continuous-monitoring duties (FAC, pH, turbidity, fluoride, UVT) show as continuous rather than grab samples: they are analyser or SCADA obligations, not lab trips. Cyanobacteria visual inspections are operator field tasks, costed at no lab fee.
Scenario. The mandatory minimum is exactly what the Rules require. Compliance margin (Premium) adds distribution FAC grabs so one low result cannot fail the percentage rule (D2.7 80%, D3.RD.3 85%). Lowest risk (Premium) lifts FAC to the maximum frequency and raises E. coli monitoring above the minimum to shorten the contamination-detection window. Metals and other monitoring-rule determinands stay at the minimum. The lab cost is analysis fees only; it excludes sampler labour, travel and courier.
Site guidance. Tick it to show, under each determinand, the kind of location the Rules expect that sample to come from (for example peripheral and central points, reservoir exits, or first-draw consumer taps). It is guidance only and does not change the schedule or the cost.
The % tag marks the rule assessed as a percentage of samples.
Calendar
Guide: using this tab
From annual frequency to actual dates. DWQAR 2026 sets counts such as "12 samples per month" or "twice monthly" but not the weekday, or how to handle stat holidays. This view runs the compliance year (1 July to 30 June), bunches same-day samples into sampler trips, holds the D3.RD.4 maximum-days-between-samples limit and the D3.MM.2 weekend minimums as hard constraints, prefers weekdays and avoids stat holidays where it can, and puts long-cycle items (3-yearly, 10-yearly) in the year you mark them due.
Weekends and holidays are preferences, not switches. The scheduler keeps every sample on a weekday and off stat holidays wherever it can, and yields to a weekend or holiday only when the preference would breach a rule's maximum-days-apart limit; it never stretches a gap past the legal maximum to dodge a weekend. So a weekend sample appears only where the tight FAC tiers (20 to 24 a month, 2-day gap) force it, where the D3.MM micro rule needs Saturday and Sunday cover above 25,000 people, or where the Christmas period leaves no working day inside the gap. The notes below say how many weekend samples remain and why, and flag any on a stat holiday so you can arrange cover. The default sampling weekday moves monthly and quarterly samples toward your chosen day; tightly spaced rows need a spread of weekdays, so it has little effect there.
Multi-year items appear only when marked due on the source (Setup tab). Each is independent. Change the compliance year (here or on Setup; they are the same year) and re-tick to plan a different year.
Cost is lab fees only. The annual lab cost is analysis charges (unit price × samples per year) and matches the Schedule tab. For full operating cost, add your sampler rate × the sampler trips plus a travel allowance per trip.
Site guidance labels each sampling day with the kind of location it should be (for example the DBP rounds alternate peripheral and central, D3.RD.10). It is guidance only and does not change dates or cost.
Day colours are prompts to look, not instructions to act. Hover or tap a day for its samples.
Scenarios
Guide: using this tab
The three scenarios trade sampling cost against two different benefits: FAC compliance headroom, and faster contamination detection.
- Mandatory minimum: exactly what the Rules require and the lowest cost. The basis for the schedule and calendar unless you choose otherwise.
- Compliance margin: lifts distribution FAC grab sampling (D3.RD.3 at least 0.2 mg/L in more than 85% of grabs; D2.7 at 80%) one step. These are the only determinands assessed as a percentage of samples, so a single low reading is a bigger share of a small set than a large one. A few extra grabs mean one outlier no longer tips the period into non-compliance. E. coli, metals, turbidity and pH have no percentage to buy headroom against, so they are unchanged.
- Lowest risk: lifts distribution FAC to the maximum grab frequency (two steps up) and raises E. coli and total coliform monitoring one rung above the minimum. E. coli has no percentage-of-samples allowance under DWQAR 2026 (any detection triggers a response), so the extra micro sampling buys no compliance tolerance; its value is detecting a contamination event sooner, which lowers actual supply risk. The costliest scenario.
Absolute limits and continuous-monitoring duties stay at the mandated minimum in every scenario. The comparison shows what the extra lab spend buys: how many low FAC results each scenario can absorb, and how much sooner contamination would be caught.
Report & Save
Guide: using this tab
Tick the scenarios to include, then make a PDF report, or download the schedule and calendar as spreadsheets for procurement and lab briefs. Spreadsheets carry a Scenario column so several scenarios compare in one file.
The project file saves your whole supply setup and Settings so you can open it later, on another computer, or share it with a colleague. Everything you enter is also kept in this browser automatically.