Part G fittings approach vs full calculation: which do you need?
Most new homes can show Part G compliance without a calculation at all. Whether yours can depends on a short list of fittings.
The fittings approach
Approved Document G includes two tables of maximum fitting figures. If every fitting in the dwelling is at or below the figure in the right table, the home complies (Approved Document G).
| Fitting | Table 2.1 (125 litres) | Table 2.2 (110 litres) |
|---|---|---|
| WC | 6/4 litres dual flush or 4.5 litres single flush | 4/2.6 litres dual flush |
| Shower | 10 l/min | 8 l/min |
| Bath | 185 litres | 170 litres |
| Basin taps | 6 l/min | 5 l/min |
| Sink taps | 8 l/min | 6 l/min |
| Dishwasher | 1.25 l/place setting | 1.25 l/place setting |
| Washing machine | 8.17 l/kg | 8.17 l/kg |
When you need the full calculation
The full calculation is needed if any of these apply:
- Any fitting is above its figure in the table.
- There's no shower.
- There's a waste disposal unit.
- There's a water softener.
- There's grey water or rainwater reuse.
Why the full calculation is often better anyway
The fittings approach is all or nothing. One fitting over the limit and it no longer applies, even if everything else is well under. The full calculation lets fittings balance each other. A bigger bath can be offset by a lower flow shower. A rainfall shower can work if the WCs and taps are efficient.
That flexibility is often what clients want. It also shows you exactly how much room is left, which helps when someone changes the spec late on.
The quick answer
Enter the fittings into the calculator. It works out the full figure and also tells you whether the fittings approach applies, so you can use whichever route suits the job.
Run the numbers
The free calculator checks a dwelling against 125 or 110 litres, shows where the water goes, and finds the smallest change that passes.