WaterMonkey
Part G water efficiency
AD G · Reg 36
AD G · Reg 36
💡 Save money by bundling: one report covers any number of identical plots for one fee — group dwellings that share the same sanitaryware into a single type and list the plots it covers. Extra types in the same report are only £15 +VAT each.
Presets fill the selected dwelling type with realistic starting values — then tweak to match the actual specification.
One type = one set of sanitaryware, not one plot. If plots 1–4 and 7 all have the same shower, WC, bath and taps, that is a single type covering five plots — and a single fee.
List the plots in the box so the report says which homes it applies to. Building Control needs to see the coverage, and it is also what stops you paying for the same calculation five times.
The target is 125 l/p/d unless a planning condition imposed the optional 110. Check the decision notice — this is the single most common thing to get wrong on an otherwise correct calculation.
125 l/p/d is the standard requirement (Building Regulation 36 / AD G). 110 l/p/d applies where the optional requirement is imposed as a planning condition — check the decision notice.
All of it is manufacturer product data, off the spec sheets your sanitaryware schedule already cites. You only ever fill the Capacity / flow column — the use factors and fixed allowances are set by the DCLG methodology and cannot be changed.
Several different specs of the same fitting? Use the multiple-fittings button on that row: the official rule takes the greater of the average and 70% of the highest, so one ultra-low fitting cannot drag the average down.
Over target? The shower is almost always the biggest single item, with the WC second. The result panel names the one change that would fix it.
This is Regulation 36 set out line by line, and none of it is editable — it is arithmetic on the fittings above.
The verdict is judged on the unrounded row 11, so a spec displaying exactly 125.0 can still fail on the true decimal. Leave yourself a little headroom — installed spec has a way of drifting from what was drawn.
Defra has proposed cutting the Part G standard from 125 to 105 l/p/d (and the optional standard from 110 to 100), intended during 2026 with a six-month transition. Proposal only — not in force: today's standards remain 125 and 110.
Branded 2-page report for Building Control submission.
£25 +VAT first dwelling type · £15 +VAT each additional type (£30 / £18 inc VAT).
See an example report
The report is a professionally formatted PDF issued by Energycount Limited — branded cover page with the compliance result, plus the full Water Efficiency Calculator (Table 1) for every dwelling type — ready for submission to Building Control.
💡 One dwelling type covers every identical plot on the scheme at no extra cost — bundle dwellings that share the same sanitaryware. Not sure? View an example report. Included: your branded PDF with a unique Report ID (verifiable at energycount.co.uk/verify), re-download of the same report free for 24 hours, and free re-export for genuine corrections within 1 hour (up to 5). Material changes to the fittings count as a new calculation. A VAT invoice is emailed automatically — add your company name and VAT number at checkout.
Secure payment via Stripe · Your project is saved in this browser and restored after payment. By paying you agree to our Conditions of Sale — the report is supplied immediately, so the 14-day cancellation right is waived on delivery.
Only consumption beyond the 4% good-practice level counts. If the result is zero or negative, zero is used.
You are producing one number: litres per person per day, for each dwelling type. If it lands at or under the target, the dwelling complies with Regulation 36 and Approved Document G.
Almost all of it comes from Table 1 — the fittings. Everything else is the project header, an optional recycling system, or arithmetic the tool does for you.
Each fitting contributes capacity or flow rate × a fixed use factor, plus a fixed allowance. The use factors come from the DCLG methodology and are not adjustable — they are the regulation's assumptions about how often people use things, not a prediction about your occupants.
Then the totals run exactly as Regulation 36 sets them out:
| Row | What it is |
|---|---|
| (5) | Total calculated use from Table 1 |
| (6)(7) | Less any greywater and rainwater contribution |
| (8) | Normalisation factor — × 0.91 |
| (9) | Total water consumption = [(5) − (6) − (7)] × 0.91 |
| (10) | External water use — a flat + 5.0 l/p/d |
| (11) | Total for Regulation 36 = (9) + (10) — this is the number that must meet the target |
The verdict is judged on the unrounded row 11. A spec that displays as exactly 125.0 can still fail on the true decimal, which is why a little headroom is worth having.
125 l/p/d is the standard requirement under Regulation 36 and AD G. 110 l/p/d is the optional requirement, and it only applies where it has been imposed as a planning condition — check the decision notice rather than assuming. If in doubt, ask the case officer; designing to 110 unnecessarily costs the client money, and designing to 125 when 110 was conditioned costs a discharge of condition.
All of it is manufacturer product data, and all of it is on the spec sheets your sanitaryware schedule already references:
More than one spec of the same fitting? Use the multiple-fittings button on that row. The official rule takes the greater of the average and 70% of the highest, so one ultra-low fitting cannot drag the average down.
Greywater recycles water from baths, showers and basin taps to flush WCs or feed a washing machine. The saving is the smaller of what the system can supply and what those uses actually demand — a big system feeding one WC saves only what that WC uses.
Rainwater follows BS 8515. The intermediate method works the yield out from roof area, a yield coefficient and annual rainfall; direct entry lets you type a figure straight off a system specification. If greywater is already meeting some of the same demand, the tool caps the rainwater saving so the two cannot be counted twice.
Water softeners only count for the water they consume beyond the 4% good-practice level. If the result is zero or negative, zero is used.
A dwelling type is one set of sanitaryware, not one plot. Group every plot that shares a spec into a single type and list them in the plots box: one fee covers all of them. Extra types in the same report are £15 +VAT each, against £25 +VAT for the first.
It implements The Water Efficiency Calculator for New Dwellings (DCLG, 2009), as required by Approved Document G and Building Regulation 36, with every row shown so Building Control can check it. The calculated figure is a compliance metric, not a prediction of actual use.
Every paid report carries a unique ID your Building Control body can verify in seconds. Stuck? Get in touch or call 01202 623236.