Plumbing

Domestic water

Peak

0,27l/s

Pipe

18 × 1,0

Velocity

1,35m/s

Domestic water calculates the peak flow to DIN 1988-300. Outlets and the building type give the simultaneous volume flow. Pipe size, velocity and the pressure loss of the run follow from that peak.

Flow rate

0,27

l/s

Velocity

1,35

m/s

18 × 1,0Copper

Litres per minute
16,3l/min
Cubic metres per hour
0,98m³/h
Inside
16,0mm
Friction
1.512Pa/m
Sum VR
0,35l/s

Input

Building

Washbasin

0,07 l/s · DN 15

1

Shower

0,15 l/s · DN 15

1

Bath

0,15 l/s · DN 15

0

Kitchen sink

0,07 l/s · DN 15

0

Dishwasher

0,07 l/s · DN 15

0

Washing machine

0,15 l/s · DN 15

0

WC cistern

0,13 l/s · DN 15

1

Urinal (cistern/automatic)

0,07 l/s · DN 15

0

Urinal (flush valve)

0,30 l/s · DN 15

0

Utility sink

0,30 l/s · DN 15

0

Flush valve DN 20

1,00 l/s · DN 20

0

Pipe

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How it's calculated

Peak flow follows DIN 1988-300. The sum of the design flows is combined with the building constants a, b and c as VS = a · sum^b − c, and is limited by the largest single outlet and by the sum. An office building uses a = 0.91, b = 0.31 and c = 0.38, the same as a school. Pipe size is the smallest whose velocity stays within the target. Friction is shown, but it does not decide the size.

Worked example

Office, sum of VR = 1.20 l/s, largest single outlet 0.15 l/s: peak flow 0.58 l/s.

FAQ

Which building types are there?
Residential, school, office building, hotel, hospital ward building and care home. The constants are those of the standard.
How much flow does a washing machine need?
0.15 l/s under DIN 1988-300 (formerly 0.25 l/s under DIN 1988-3). A utility sink is 0.30 l/s. A urinal with a cistern or automatic flush is 0.07 l/s, and one with a flush valve is 0.30 l/s.
Why is the peak smaller than the sum?
Not every outlet runs at once. The DIN 1988-300 formula reduces the sum, but it does not go below the largest single outlet.
Is pressure drop used to choose the pipe?
No. The size follows the target velocity. The pressure gradient is only reported.