Discharge Unit Values BS.5572 :1978

Type of Sanitary Fitting Interval between Use

Domestic Public Peak Flow DischargeUnit

(min) (min) (min) Value

Automatic Washing Machine 410 20

5 40

WC (9 Litre Cistern) 20 710 14

5 28

Sink 20 610 14

5 27

Wash Basin 20 110 3

5 6

Bath 75 710 18

- -

Shower (Per Head)Domestic 1Public 2

Urinal Bowl 20 0.3

Discharge Unit Maximum Values BS.5572 :1978

Internal diameter Fallof pipe (mm) 1 in 111 1 in 45 1 in 22

100mm 230 430 1050

125mm 780 1500 3000

150mm 2000 3500 7500

Rates of Discharge from Sanitary Fittings BS.5572 :1978

Type of Fitting Discharge (litres per second)

Basin 0.60

Bath 1.00

Sink (32mm Diameter Waste) 0.50

Sink (38mm Diameter Waste) 1.00

Sink (50mm Diameter Waste) 2.00

Urinal 0.15

WC (9 or 14 litre cistern) 2.30

Shower 1.00

Equipment Washer 5.70

Steam Steriliser 0.95

Peak Simultaneous Demand

Simultaneous Demand FactorThe discharge unit value takes into account the number of fittings discharging simultaneouslycompared with the total number of fittings installed.

known as the usage ratio T,

n = total number of fittings installed

t = time in seconds fittings are discharging

T = time in seconds between usage

Total number of fittings installed (n) = 30It has been assumed that each fitting will take 10sec to discharge their contents, and will be used at 900sec intervals

.= 0.11 900

.= 5.10 + square root of 5.874

.= 5.10 + 2.42

.= 7.52

Simultaneous Demand Factor = 7.52%

m = np + 1.80 [2 np (1 - p] 0.5

Where m = number of fittings discharging simultaneously

p = t

p = 10

m = (30 x 0.11) + 1.80 [2 x 30 x 0.11 (1 - 0.11)] 0.5

Residual Drainage Network Pipe Sizing

The following calculations indicate the pipework sizes of the main horizontal sections.The size of branch mains is calculated on the basis that the discharge pipe shall be at least equal to the diameter of the outlet on the appliance to which it is connected.

Section 1.

Sink (38mm waste) 4 x 1.00 l/s = 4.00 l/s

Sink (50mm waste) 4 x 2.00 l/s = 8.00 l/s

12.00 x 7.52% = 0.90 l/s or 0.0009m3/s

Q = VA

0.0009 x 8 = 0.0072

0.0072 / 1 x 3.142 = 0.0023m

Square root of 0.0023m = 0.048m

Section 2.

Sink (38mm waste) 4 x 1.00 l/s = 4.00 l/s

Sink (50mm waste) 5 x 2.00 l/s = 8.00 l/s

Equipment Washer 1 x 5.70 l/s = 5.70 l/s

17.70 x 7.52% = 1.33 l/s or 0.0010m3/s

Q = VA

0.0010 x 8 = 0.008 m3/s

0.008 / 1 x 3.142 = 0.0025m

0.048m x 1000 = 48mm

Suggested horizontal pipe size is 80mm Nominal Bore

= V x π/8 D2 (Half Bore)

D = Square Root Q x 8 / V x π

= V x π/8 D2 (Half Bore)

D = Square Root Q x 8 / V x π

Square root of 0.0025m = 0.05m

Section 3.

Sink (38mm waste) 2 x 1.00 l/s = 2.00 l/s

Sink (50mm waste) 7 x 2.00 l/s = 14.00 l/s

Equipment Washer 2 x 5.70 l/s = 11.40 l/s

Steam Steriliser 3 x 0.95 l/s = 2.85 l/s

30.25 x 7.52% = 2.27 l/s or 0.0023m3/s

Q = VA

0.0023 x 8 = 0.0184 m3/s

0.0184 / 1 x 3.142 = 0.0059m

Square root of 0.0059m = 0.077m

Section A.

17 Sinks @ Peak Flow = 17 x 27 = 459 Loading Units1 Washer @ Peak Flow = 1 x 40 = 40 Loading Units

Total Loading Units = 499 LU

From BS 5772 :1978

100mm Nominal Bore @ 1:22

Section B.

8 Sinks @ Peak Flow = 8 x 27 = 216 Loading Units

0.05m x 1000 = 50mm

Suggested horizontal pipe size is 80mm Nominal Bore

0.077m x 1000 = 77mm

Suggested horizontal pipe size is 80mm Nominal Bore

= V x π/8 D2 (Half Bore)

D = Square Root Q x 8 / V x π

5 Washer @ Peak Flow = 5 x 40 = 200 Loading Units

Total Loading Units = 416 LU

From BS 5772 :1978

100mm Nominal Bore @ 1:45