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The University of Sheffield

FINAL REPORT

PERFORMANCE EVALUATIONS: THE XETRO SIPHONIC ROOF DRAINAGE OUTLET

Professor Adrian J SaulGlenn BrawnPaul Osborne

April 2005

1

Contents

Page No

1.0 Introduction 3

2.0 Details of XETRO PRODUCTS siphonic outlet and roof gutter arrangement 3

3.0 Programme of Tests 4

4.0 Results and Discussion 4

4.1 Tests on single upstream outlet 44.2 Tests on single upstream outlet 44.3 Tests with dual outlets in combination 44.4 Discussion 54.5 Comparison of performance of XETRO PRODUCTS outlet 5

with previously published work

5.0 Conclusion 5

Acknowledgements 6

Figures

Figure 1 Water depth versus flowrate: single upstream outletFigure 2 Water depth profile upstream of a single outlet at

different steady flowratesFigure 3 Comparison of flow depths at location 500mm

upstream and downstream of the downstream outlet

Figure 4 Depth flowrate relationship: dual outletsFigure 5 Depth profile with dual outlets

TablesTable 1 Results: Single upstream outletTable 2 Results: Single downstream outletTable 3 Results: Dual outlet

PlatesPlate 1a XETRO PRODUCTS outlet showing complex

transition between square inlet and circular outletPlate 1b XETRO PRODUCTS outlet with low flow to inlet

Plate 2 XETRO PRODUCTS anti vortex platePlate 3 XETRO PRODUCTS leaf guardPlate 4 Roof gutter system and depth gaugePlate 5a Siphonic pipework: upstream outletPlate 5a Siphonic pipework: downstream outlet

Plate 6 Flow pattern at outlet: low flowPlate 7 Flow pattern at outlet: medium flow Plate 8 Flow pattern at outlet: flow capacity

2

1.0 INTRODUCTION

The University of Sheffield was commissioned by XETRO PRODUCTS to test the performance of a new form of siphonic roof drainage outlet, known as the XETRO Siphonic System. The primary aim of the study was to assess the hydraulic performance of the outlet, in the form of a depth discharge relationships, and hence, to establish the hydraulic capacity of the outlet. Tests were completed on single outlets and with two outlets equally spaced along the same gutter length. Subsequently the results will provide the opportunity to calibrate and verify a mathematical model that describes the design performance of the XETRO system for use by practicing engineers.

2.0 DETAILS OF THE XETRO PRODUCTS OUTLET AND ROOF GUTTER ARRANGEMENT

The XETRO PRODUCTS Siphonic outlet was designed by Mr John Smith and has a square outlet bowl that sits flush with the base of the gutter and a series of unique 3D curves to form a transition to the circular outlet, of diameter 90mm, at the base of the bowl. The complex shape of the outlet is shown in Plate 1a whilst Plate 1b records the flow pattern within the outlet at a low flowrate. The outlet has a square anti-vortex device (Plate 2) and a square leaf guard (Plate 3). Hence the primary difference between the XETRO PRODUCTS outlet and existing siphonic outlets is that of the outlet plan shape, square Comparisond to circular, and of the corresponding increase in the weir length of the outlet (created by the square shape) and the complex transitional shape to the central outlet that connects to the circular downstream pipework.

The XETRO PRODUCTS outlet was tested in the unique roof gutter test rig, located on the flat roof area above the Structures Laboratory of the Department of Civil and Structural Engineering at the University of Sheffield. This system is shown in Plate 4. The system is 35m long and has a roof width of 1.2 m inclined at an angle 12 degrees to the horizontal. The roof area is supplied with water from the sump in the Water Engineering Laboratory at the University of Sheffield via 3no 110mm diameter pipes to a channel that runs the full length of the rig. This channel, located at the upstream end of the roof incorporates a horizontal thin plate overflow weir that allows the water to spill onto the roof and to create a uniform flow depth over the complete length of the roof. The inflow to this channel was computer controlled to the required flowrate.

The water was drained from the roof area into a trapezoidal gutter with base width 600mm and side slopes with an internal angle of 110degrees. The height of the gutter was 110mm. Two XETRO PRODUCTS outlets were used in the tests and these were placed centrally in the base of the gutter with the centre of each outlet located 8.75m from each end of the gutter. Hence the distance between the outlets was 2 x 8.75 = 17.5m. The flow through the outlets was discharged into the vertical length of the siphonic pipework system of diameter BBB mm. Hence a short transition pipe was required to link the 100mm outlet and the 90mm downstream pipework, as can be seen in Plates 5a (upstream outlet) and 5b (downstream outlet). The flow in the siphonic pipe system was returned to the Water Engineering Laboratory where each flowrate through the XETRO PRODUCTS outlet was measured volumetrically.

The depth of flow in the chamber was measured at 100mm spaced intervals along the length of the gutter both upstream and downstream of each XETRO outlet with the measurement recorded at the centreline of the gutter base. The depth gauge used to record the flow depth at each point is also shown in Plate 4. All depth measurements were referenced to the elevation of the base of the gutter at the measurement point.

3

Plate 1a XETRO PRODUCTS outlet showing complex transition between square inlet and circular outlet

4

Plate 1b XETRO PRODUCTS outlet with low flow to inlet

Plate 2 XETRO PRODUCTS anti vortex plate

5

Plate 3XETRO PRODUCTS leaf guard

Plate 4 Roof gutter system and depth gauge

6

Plate 5a Siphonic pipework: upstream outlet

Plate 5b Siphonic pipework: downstream outlet

7

Plate 6 Flow pattern at outlet: low flow

Plate 7 Flow pattern at outlet: medium flow

8

Plate 8 Flow pattern at outlet: flow capacity

9

3.0 PROGRAMME OF TESTS

Three tests were completed to measure the hydraulic performance of the XETRO PRODUCTS outlets. Firstly the capacity of each individual outlet was measured. These were identified as the upstream outlet and the downstream outlet. Secondly, the combined performance of the two outlets was recorded.

In each teat a series of flowrates were used and, following a period of time that allowed the flow conditions to become steady (constant depth with time), the depth profile along the gutter length was recorded both upstream and downstream of each outlet. The performance of the system was tested upto the point that the outlet was drowned out.

In summary therefore the test programme recorded the flowrate-depth relationship for the following outlets:

Test 1 Single upstream outlet (downstream outlet blocked)Test 2 Single downstream outlet (upstream outlet blocked)Test 3 Dual outlets in combination

4.0 RESULTS AND DISCUSSION

The results of all tests are detailed in Table 1(single upstream outlet), Table 2 (single downstream outlet) and Table 3 (dual outlets). All results have been plotted to give the flow depth relationship to each outlet, included in Appendix 1, whilst Appendix 2 records plots of the depth profiles to each outlet for selected flowrates.

10

11

CHANNEL DEPTH SINGLE OUTLET UPSTREAMFLOW RATE U200 U300 U400 U500 D200 D300 D400 D500 D600 C/L

l/s mm mm mm mm mm mm mm mm mm mm8.6 37.6 40.9 40.1 39.0 36.5 34.5 34.6 35.2 - 49.411.3 42.3 46.1 45.5 42.5 38.6 40.0 39.1 39.4 - 53.012.5 46.5 46.0 47.1 46.5 40.5 40.8 41.7 42.0 - 57.214.5 52.1 53.7 53.3 51.1 45.6 46.2 46.0 47.5 - 63.919.3 64.0 66.4 64.8 64.4 55.5 56.1 58.5 58.7 59.2 76.622.9 73.8 74.8 75.2 75.2 63.9 67.0 67.5 69.1 68.8 85.825.0 84.9 85.9 85.8 85.9 75.0 76.7 78.1 79.8 81.9 94.625.2 94.0 94.4 94.4 93.6 85.4 87.5 87.6 89.9 90.2 99.025.2 123.0 124.5 124.9 125.4 121.9 123.0 125.0 126.5 128.0 124.0

25.7? FLOOD TEST STOPPED

CHANNEL DEPTH SINGLE OUTLET DOWNSTREAMFLOW RATE U200 U300 U400 U500 D200 D300 D400 D500 D600 C/L

l/s mm mm mm mm mm mm mm mm mm mm8.6 32.7 32.6 33.0 - 33.1 34.7 34.5 - - 35.510.3 36.0 36.6 33.0 - 38.9 38.7 38.1 - - 41.412.5 40.1 40.1 39.8 - 39.9 42.4 42.0 42.1 - 46.014.6 44.8 45.4 45.7 44.7 46.1 47.5 48.0 47.9 - 53.219.6 54.4 55.6 55.6 54.9 57.8 60.0 59.9 59.7 - 65.823.0 64.1 65.5 65.3 64.4 68.7 69.9 70.5 70.4 - 75.024.8 76.5 78.5 78.1 78.5 82.6 83.0 83.2 83.2 - 84.725.2 93.0 94.1 95.0 95.0 99.3 101.1 101.3 101.4 - 93.5

Table 2 Results: Single Downstream Outlet

Table 1 Results: Single Upstream Outlet

CHANNEL DEPTH UPSTREAM OUTLETFLOW RATE U200 U300 U400 U500 D200 D300 D400 D500 D600 C/L

l/s mm mm mm mm mm mm mm mm mm mm8.6 20.3 20.5 20.4 - 17.7 17.9 17.9 18.0 - 24.912.0 24.3 24.8 24.8 - 22.5 22.5 23.5 24.1 - 30.019.4 31.6 32.9 33.1 - 29.0 30.4 31.0 31.2 - 39.625.0 38.7 40.8 40.8 - 34.9 35.8 37.5 38.0 - 48.527.8 41.8 43.5 43.7 - 38.5 38.9 39.5 41.5 - 53.029.4 44.5 45.4 45.7 - 40.2 41.0 41.0 44.0 - 56.031.6 47.5 49.5 49.5 - 42.9 44.7 45.5 47.4 - 58.833.6 86.6 88.7 87.8 - 84.4 85.7 86.5 87.6 - 86.0

OUTLETS DROWNED OUT

CHANNEL DEPTH DOWNSTREAM OUTLETFLOW RATE U200 U300 U400 U500 D200 D300 D400 D500 D600 C/L

l/s mm mm mm mm mm mm mm mm mm mm8.6 28.2 28.0 28.2 - 29.5 30.4 30.5 30.5 - 24.912.0 30.1 30.5 30.2 - 31.8 32.3 32.3 32.3 - 30.019.4 37.8 38.6 38.7 - 37.0 39.8 39.2 39.7 - 39.625.0 44.3 48.0 47.9 - 46.0 48.9 49.1 49.4 - 48.527.8 46.0 47.3 48.4 - 50.0 51.9 51.8 51.6 - 53.029.4 56.2 56.7 54.6 - 53.6 56.8 57.9 58.2 - 56.031.6 58.7 59.7 59.4 - 58.2 60.1 60.3 61.4 - 58.833.6 97.8 98.0 97.9 - 100.0 101.1 101.0 101.1 - 86.0

OUTLETS DROWNED OUT

Table 3 Results: Dual Outlets

Specific results for each test are now discussed.

4.1 Single upstream outlet (downstream outlet blocked).A typical result for this outlet is shown in Figure 1. This highlights that the capacity of the system, which is a function of the pipework system downstream of the outlet, is 25 litres/s. Figure 2 records the flow depth to either side of the outlet which indicates a dominant influence due to the higher volume of flow that approaches the outlet from the downstream side. This restricts the flow from the upstream side and is clearly evidenced by reference to Plates 6-8, which highlight the flow regime to this outlet at flowrates of TT, HH, and HH litres/s. At low flowrates the flow patterns around the leaf guard are uniform whereas at medium flowrates the there is a clear influence on the flow pattern with a visible change in the flow depth across the face of the leaf guard. The flow depth is again uniform when the capacity of the system is approached.

4.2 Single downstream outlet (upstream outlet blocked)The results for this outlet show similar trends to that of the upstream outlet and again the capacity of the system is 25 litres/s. Figure 3 shows a comparison of the flowrate-depth relationship measured 500mm upstream and downstream of the downstream outlet and clearly slight differences may be observed. This is expected due to the different locations of the outlet within the gutter length and due to the fact that the same pipework downstream of the outlet was used in each of the tests. Of importance is the result that both the upstream and the downstream outlets both have the same capacity, circa 25 litres/s.

4.3 Dual outlets in combinationA typical result for the flow-depth performance of the dual outlets is shown in Figure 4, which highlights that, the capacity of the two outlets, within this gutter pipework system was approximately 33 litres/s. A plot of the depth profiles corresponding to the dual performance is shown in Figure 5 which highlights that at the low to medium flowrates there is a change in depth due to flow direction but at the high flowrate, the depth in the gutter becomes almost constant as the flow capacity of the system is approached.

4.4 DiscussionThe performance evaluations highlighted that the XETRO PRODUCTS siphonic roof drainage outlet performed well with the development of siphonic action.

This report presents a series of results that may subsequently be used for the calibration and verification of a mathematical model that predicts the performance of the system for design purposes.

4.5 Comparison of the performance of the XETRO PRODUCTS outlet with previously published work

Previous work, which is directly comparable to the results of this study, was published by Bramhall and Saul (1998, 1999a and 1999b) who reported in the performance of the Fullflow siphonic roof drainage outlets. These outlets were 260mm diameter. Apart form the change in the geometry and size of the outlet, the results from this study are directly comparable to the dual outlet results presented by Bramhall and Saul. The comparison shows that, at each flowrate, the flow depth in the gutter for the XETRO PRODUCTS outlet was, in general, slightly less than that reported by Bramhall and Saul and that the capacity of the XETRO dual outlet was slightly greater. These results confirm that the XETRO system has considerable potential and it is recommended that further work is completed to assess the influence of the capacity of the downstream pipework.

12

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)

CapacityU200U300U400U500C/L

Figure 1 Water depth versus flowrate: single upstream outletNote U200 denotes measurement point 200mm upstream of outlet centre line etc and CL

represents a measurement 8.75m upstream

0

10

20

30

40

50

60

70

80

90

100

0 2000 4000 6000 8000

Distance from outlet (mm)

Dep

th (m

m)

8.612.525.0

Flow (l/s)

Figure 2 Water depth profile upstream of a single outlet at different steady flowrates

13

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)

UpstreamDownstream

Figure 3 Comparison of flow depths at location 500mm upstream and downstream of the downstream outlet

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)

CapacityU200U300U400C/L

Figure 4 Depth flowrate relationship: dual outlets

14

0

10

20

30

40

50

60

8000 12000 16000 20000 24000 28000

Distance from u/s end (mm)

Dep

th (m

m)

8.62531.6

Flow (l/s)

u/s

outle

t

cent

relin

e

d/s

outle

t

Figure 5 Depth profile with dual outlets

5.0 CONCLUSION

Tests have been completed on the XETRO PRODUCTS siphonic roof outlet within the siphonic roof drainage rig at the University of Sheffield. The performance of the system showed that the outlet generated siphonic drainage conditions and that the flow pattern to the outlet allowed these conditions to be maintained over the duration of the tests.

The hydraulic performance of the XETRO PRODUCTS outlet was good and Comparisond favourably to the results from previously published work.

The results of the report are specific to the configuration of the test facility used but will provide valuable information for the calibration and verification of a mathematical model that describes the hydraulic performance of the XETRO PRODUCTS siphonic roof drainage system

6.0 REFERENCES

Bramhall M and Saul A J (1998)Hydraulic Performance of Siphonic Rainwater Outlets.Proc CIB W62 International Symposium on Water Supply and Drainage for Buildings, Rotterdam, September, 1998.

Bramhall M.A and Saul A.J. (1999a)Hydraulic performance of siphonic rainwater outletsProc. 8ICUSD, Sydney, August.

Bramhall M.A and Saul A.J (1999b)The effect of outlet position on the performance of siphonic rainwater drainage systemsProc CIB W62 Water Supply and Drainage for Builbings Symposium, Edinburgh, September

15

7.0 ACKNOWLEDGEMENTSThe authors are grateful to John Smith and Steve Maltby of XETRO PRODUCTS for their kind support and advice through the duration of the project.

16

APPENDIX 1

Depth flowrate plots for all tests

17

Single outlet

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)


Upstream outlet, upstream depths

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)

CapacityC/LD200D300D400D500D600

Upstream outlet, downstream depths

18

Single outlet

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)


Downstream outlet, upstream depths

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)

CapacityC/LD200D300D400D500

Downstream outlet, downstream depths

19

Single outlet

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)

UpstreamDownstream

U200 Comparison u/s and d/s.

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)

UpstreamDownstream

U300 Comparison u/s and d/s

20

Single outlet

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)

UpstreamDownstream

U400 Comparison u/s and d/s depths

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)

UpstreamDownstream

U500 Comparison u/s and d/s depths

21

Single outlet

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)

UpstreamDownstream

c/l Comparison u/s and d/s depths

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)

UpstreamDownstream

D200 Comparison u/s and d/s depths

22

Single outlet

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)

UpstreamDownstream


0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)

UpstreamDownstream


23

Single outlet

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)

UpstreamDownstream


24

Dual outlet charts

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)


Upstream outlet, upstream depths

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)


Upstream outlet, downstream depths

25

Dual outlet charts

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)


Downstream outlet, upstream depths

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)


Downstream outlet, downstream depths

26

Dual outlet charts

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)

UpstreamDownstream

U200 Comparison u/s and d/s outlets

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)

UpstreamDownstream


27

Dual outlet charts

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)

UpstreamDownstream


0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)

UpstreamDownstream

c/l Comparison u/s and d/s outlets

28

Dual outlet charts

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)

UpstreamDownstream

D200 Comparison u/s and d/s outlets

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)

UpstreamDownstream


29

Dual outlet

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)

UpstreamDownstream

D400 comparison u/s and d/s outlets

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)

UpstreamDownstream


30

Comparison of Single and Dual outlets

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)

Single UpstreamSingle DownstreamDouble UpstreamDouble Downstream

U200

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)


U300

31


0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)


U400

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)


C/L

32


0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)


D200

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)


D300

33

Comparison Single and Dual outlet charts

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)


D400

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Flow Rate (l/s)

Dep

th (m

m)


D500

34

APPENDIX 2

Depth profiles

35

Single, upstream outlet, depths upstream

0

10

20

30

40

50

60

70

80

90

100

0 2000 4000 6000 8000


Dep

th (m

m)

8.612.525.0

Flow (l/s)

Single, upstream outlet, depths downstream

0

10

20

30

40

50

60

70

80

90

100

0 2000 4000 6000 8000


Dep

th (m

m)

8.612.525.0

Flow (l/s)

36

Single, downstream outlet, depths downstream

0

10

20

30

40

50

60

70

80

90

0 2000 4000 6000 8000


Dep

th (m

m)

8.5512.524.8

Flow (l/s)

Dual outlet, depths around both outlets

0

10

20

30

40

50

60

8000 12000 16000 20000 24000 28000

Distance from u/s end (mm)

Dep

th (m

m)

8.62531.6

Flow (l/s)

u/s

outle

t

cent

relin

e

d/s

outle

t

37

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