The Plumbing Knowledge Hub

Estimate a home or building's total daily water demand from the number of occupants and per-person use (LPCD), with the annual figure.

Work out the peak design flow rate for sizing supply pipes and pumps using the peak-factor method, in L/min and L/s.

Size a water supply pipe — find the required internal bore from design flow and target velocity, with the nearest nominal pipe size.

Find the water velocity in a pipe from flow and internal diameter, and see instantly whether it is within the safe range or too high.

Estimate head loss in a pipe run with the Hazen-Williams equation from flow, diameter, length and C factor, in metres and bar.

Compute the total dynamic head a pump must overcome from static lift, friction, fittings and residual pressure — the input for pump sizing.

Size the overhead roof water tank for a home from occupants, per-person use and the share of the day's water it holds, with a standard tank size.

Size the underground sump water tank from occupants, per-person use and the days of storage you want to hold against supply cuts.

Convert water column height (head) into pressure in bar, kPa and psi — see how much pressure an overhead tank at a given height delivers.

Estimate a household's daily hot water demand and peak simultaneous draw, with a suggested heater or solar storage capacity.

Total the drainage fixture units (DFU) of a home's fixtures and get an indicative drain and soil-stack size.

Work out the fall a drain pipe needs from its length and slope ratio, in mm per metre and total drop.

Full-bore flow capacity of a gravity drain from diameter, slope and roughness using Manning's equation, in L/s.

Check whether a sewer or drain runs fast enough to be self-cleansing using Manning's full-bore velocity.

Estimate peak stormwater runoff from a plot with the Rational Method from area, runoff coefficient and rainfall intensity.

Find how many rainwater downpipes a roof needs from roof area, rainfall intensity and downpipe size.

Size a rainwater gutter for a roof from the plan area drained and rainfall intensity, with a nominal gutter width.

Estimate the water-hammer surge pressure from sudden valve closure with the Joukowsky equation, in bar.

Get an indicative vent (drain venting) pipe size from the soil stack served, fixture units and vent run length.

Estimate how much greywater a home generates for reuse from occupants, per-person use and the reusable share.

Estimate how much rainwater a roof can harvest in a year from its area, your annual rainfall and a collection coefficient.

Size a rainwater recharge pit from catchment area, rainfall intensity and detention time, with a suggested footprint.

Size a rainwater first-flush diverter — the initial dirty roof-wash to divert before storage — from roof area and divert depth.

Size a water softener from your hardness, daily water use and days between regeneration, with the grain capacity needed.

See how much water a domestic RO purifier rejects for the purified water you use, from your daily use and recovery ratio.

Work out how much household bleach to disinfect a water storage tank from tank volume, target chlorine dose and bleach strength.

Size a solar water heater — storage LPD and collector area — from occupants, per-person hot water and system yield.

Find how many days your water storage lasts in a supply cut from total capacity, occupants and per-person use.

Calculate how much water a length of pipe holds — for disinfection dosing, flushing and the hot-water wait — from bore and length.

Estimate the monthly cost of buying tanker water for a supply shortfall, from daily shortfall, tanker size and price.