Guidance · 4 min
What information is needed for a Part G water calculation?
The fitting data that turns a provisional sanitaryware schedule into a defensible calculation.
Fittings and appliances
Provide the proposed WC flush volumes, tap and shower flow rates, bath capacities and relevant appliance information for each dwelling specification. Manufacturer data is preferable where products are selected.
Use actual performance data
Style names or catalogue images do not establish water use. Product data should identify the performance value used in the calculation and any operating modes that apply.
If products are not selected
A preliminary calculation can use a coordinated performance specification. This gives the designer or client clear limits to use when selecting fittings later.
Resolve selectively
If the first calculation does not achieve the applicable target, test focused changes. Reducing every fitting indiscriminately can compromise usability without being necessary.
Building Regulations guidance and assessment methods can change, and transitional provisions may apply. Confirm the correct route for the particular project rather than relying on a general article.