Watercalcs
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v2.7
Getting started — how this planner works

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 below runs on that basis. For sampling before 1 July 2027 you must still work to the 2022 Rules.

To build your schedule:

  1. Pick your supply category and population. This assigns the rule modules (rule 6).
  2. Add your sources and set each source water class — this single field drives the entire S3 monitoring load.
  3. Add treatment plants and tick the chemicals you dose (these trigger chemical and DBP monitoring).
  4. Add distribution zones with their populations — these set the D3 FAC and microbiological sampling tiers.
  5. Press Generate schedule, then open the Calendar tab 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 add headroom: compliance margin lifts distribution FAC one step so one low reading can't 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.

Tap the i button (top right) for the full basis of the model, its limitations and assumptions, and the public references.

Build your supply below, then generate.

1. Supply identity

Confirms category; zone populations drive D3 tiers
Adds VP module event sampling (small & medium supplies)

2. Sources

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Source class drives the entire S3 monitoring load Under rule 8, Class A/B require a sanitary bore head and 3 years of clean E. coli / total coliform history (12 samples/yr) before they qualify — in return, protozoa treatment drops to 0-log and raw-water sampling is lighter. Class C/D (surface water and shallow / unprotected groundwater) carry the full continuous monitoring plus twice-monthly micro and the cyanobacteria regime. Class A additionally requires F-specific RNA bacteriophage monitoring (3/yr).
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Full suite, 50% MAV follow-up, and periodic items This is a plan for one compliance year, so multi-year items are a simple yes/no per source. Under Periodic sampling due this compliance year, tick the items actually due this year — the 3-yearly source metals, the 10-yearly groundwater radiological, and the periodic full DWSNZ chemical suite (organics, pesticides, herbicides, inorganics) — each independently. Ticked items are scheduled once this year and costed in full; unticked ones are left out. If a full-suite or other 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% — pick those, with a frequency, under Ongoing parameters flagged >50% MAV. Each is priced as its own determinand. Anything not in the list (e.g. antimony, a specific pesticide) can be named as a custom parameter under Settings → Detailed pricing, after which it becomes selectable here.

3. Treatment plants

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Treatment chemicals trigger T3.CH chemical monitoring Under T3.CH.3, every dosed chemical that has a MAV (and any source determinand exceeding its MAV) must be monitored monthly in treated water, reducible to annual after 12 consecutive results ≤50% MAV. Sodium hypochlorite forces weekly chlorate (T3.CH.4); chlorine dioxide forces weekly chlorite + chlorate (T3.CH.5). Fluoride, if dosed, is continuously monitored (T3.CH.6).

4. Distribution zones

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D3.RD.4 / D3.MM.2 set hard spacing and weekend rules by zone population FAC grab sampling (D3.RD.4) runs 12–24 samples/month with a maximum 2–4 day gap. Microbiological sampling (D3.MM.2) runs 4–12 samples/month and, above 25,000 people, mandates a minimum number of Saturday and Sunday samples each compliance year. Electing continuous FAC analysers (D3.RD.6) replaces the grab tiers with 2–4 analysers plus 4 confirmatory FAC + pH grabs/month (D3.RD.8).
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One zone = one sampling line here, but the Rules need multiple sites per zone The planner counts samples per zone, not sampling points. Your written sampling plan must spread those samples across several representative locations — peripheral and central, plus higher-risk / high-density areas (D3.RD.5, D2.3). DBP sites alternate between peripheral and central (D3.RD.10); microbiological sites must include storage exits and inter-supplier entry points (D3.MM.4). This does not change the sample count or cost — only where you take them.

5. Optional — Aesthetic GV suite

Not mandatory under DWQAR 2026, but commonly run to support customer-experience / complaint response. This is the full 34-determinand set from the Aesthetic Values for Drinking Water Notice 2022 (Taumata Arowai). It is costed as a single suite per sample point — set that rate under Settings → pricing (Aesthetic GV suite).

6. Lab unit prices (optional)

Used for lab-fee estimates in Scenarios and Reports. Leave blank to skip costing — the schedule still generates. Sampler labour, travel and courier are not included. Use Simple for grouped rates, or Detailed to price each test individually (e.g. arsenic and boron costing more than nitrate).

About the schedule

This is the annual sampling load derived from your supply configuration, one line per determinand and rule. Continuous-monitoring duties (FAC, pH, turbidity, fluoride, UVT) appear as zero grab samples — they are analyser / SCADA obligations, not lab trips. Cyanobacteria visual inspections are operator field tasks costed at zero lab fee.

Scenario selector (top right). The mandatory minimum is the free baseline — exactly what the Rules require. Compliance margin adds distribution FAC grabs so one low result cannot fail the percentage rule (D2.7 80% / D3.RD.3 85%). Lowest risk lifts FAC to the maximum frequency and also raises E. coli monitoring above the mandated minimum to shorten the contamination-detection window (lower supply risk, not a compliance allowance). FAC is the only determinand with a percentage-of-samples compliance rule; metals and other Monitoring-rule determinands stay at the minimum. Both are premium; the Scenarios tab compares all three. The lab cost shown is analysis fees only and excludes sampler labour, travel and courier.

Site guidance. Tick the Site guidance box to show, under each determinand, the kind of location the Rules expect that sample to be taken from — for example peripheral vs central points, reservoir exits, or first-draw consumer taps. The planner counts samples, not sites, so this is advisory: it does not change the schedule or cost, it just reminds you where each sample should sit in your written sampling plan.

Annual sampling schedule

About the calendar — and what cost includes

From annual frequency to actual dates. DWQAR 2026 specifies "12 samples per month" or "twice monthly" but stops short of saying which weekday, or how to handle stat holidays. This view runs the compliance year (1 July – 30 June), bunches same-day samples into sampler trips, treats 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 rolls long-cycle items (3-yr, 10-yr) into the year they fall due.

Weekends and holidays are a solver, not a switch. Avoid-weekends and avoid-holidays are preferences: the scheduler keeps every sample on a weekday and off stat holidays wherever it can, but yields to a weekend or holiday-adjacent day only when honouring the preference would breach a rule's maximum-days-apart limit — it never stretches the gap past the legal maximum to dodge a weekend. So a weekend sample appears only where the tight FAC tiers (20–24/month, 2-day gap) force it, the D3.MM micro rule mandates Saturday/Sunday cover above 25,000 people, or the Christmas period leaves no working day inside the gap. The insight panel tells you how many weekend samples remain and why, and flags any that had to land on a stat holiday so you can arrange cover. The default sampling weekday now genuinely shifts low-frequency (monthly / quarterly) placements toward your chosen day; tightly-spaced rows need a spread of weekdays, so it has little effect there by design.

Multi-year items appear only when marked due. A 3-yearly metals panel, the 10-yearly radiological set, or the periodic full DWSNZ suite shows on the calendar only when you tick it as due this compliance year on the relevant 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" stat reflects analysis charges (unit price × samples per year) and matches the Schedule page. It excludes the field sampler's time, vehicle, courier and bottle handling. For full operating cost, add your sampler rate × the trip count (see the "Sampler trips" stat) plus a per-trip travel allowance.

Scenario and site guidance. The Scenario selector mirrors the Schedule page — mandatory minimum is free; compliance margin and lowest risk are premium. Tick Show sampling-site guidance to label each sampling day with the kind of location it should be (e.g. the DBP rounds alternate peripheral / central per D3.RD.10); it is advisory and does not change dates or cost.

Compliance-year sampling calendar

Same year as Setup; periodic items appear only if marked due that year
 
Preferred day for weekly, monthly and quarterly rules; tightly-spaced FAC rows need a weekday spread, so it has little effect there
Workday Weekend NZ public holiday Sampling day On a weekend/holiday (unavoidable)
About scenarios — compliance headroom and detection speed

The three scenarios trade sampling cost against two distinct benefits — FAC compliance headroom, and faster contamination detection:

  • Mandatory minimum — exactly what the Rules require, no more, and the lowest cost. The default, and the basis for the schedule and calendar.
  • Compliance margin — increases distribution FAC grab sampling (D3.RD.3 ≥0.2 mg/L in >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 sample set than a large one. A few extra grabs mean one outlier no longer tips the period into non-compliance. Everything else — E. coli, metals, turbidity, pH — is a Monitoring or absolute-limit rule with no percentage to buy headroom against, so it is unchanged. Costs a little more than the minimum, not less.
  • Lowest risk — lifts distribution FAC to the maximum grab frequency (two steps up) for the most percentage-compliance headroom, and raises E. coli / total-coliform monitoring one rung above the mandated minimum. E. coli has no percentage-of-samples allowance under DWQAR 2026, so the extra micro sampling does not buy compliance tolerance — its value is detecting a contamination event sooner, which lowers actual supply risk. The closer together the samples, the shorter the window an event can go unnoticed. Costliest scenario.

Absolute pass/fail limits and continuous-monitoring duties are left at the mandated minimum in every scenario — tightening the threshold itself is not something extra grabs can do.

Mandatory minimum is the free baseline; compliance margin and lowest risk are premium. The comparison below quantifies what the extra lab spend buys — how many bad results each scenario can absorb, and how much sooner contamination would be caught.

Scenario comparison

Side-by-side breakdown

About reports & save

Download your schedule and calendar as CSV for procurement and lab briefs, or save your full supply configuration to a file so you can reload it later or share it with a colleague. Choose which scenarios to include in each export below. Everything you enter is also kept in this browser automatically.

Scenarios to include in exports

CSV exports include a Scenario column so you can compare selected scenarios in one file.

Schedule & calendar exports

Save & restore configuration

Your inputs auto-save in this browser. To keep a permanent copy, move between machines, or share with a colleague, download a configuration file and load it back here.