GB2502515A

GB2502515A - Roof outlet drainage flow restrictor for limiting the speed at which water leaves a flat roof.

Info

Publication number: GB2502515A
Application number: GB1208314.3A
Authority: GB
Inventors: Andrew Reginald Lee; Geraint Jones
Original assignee: Alumasc Group PLC
Current assignee: Alumasc Group PLC
Priority date: 2012-05-11
Filing date: 2012-05-11
Publication date: 2013-12-04
Anticipated expiration: 2032-05-11
Also published as: GB201208314D0; GB2502515B

Abstract

The restrictor 10 provides a predetermined reduced limited flow rate through an outlet at a given depth of water above the outlet. The restrictor is for fitting onto a discharge pipe or spigot 14 and in use and may have a flow control aperture which is smaller than the diameter of the pipe it is fitted to. The restrictor is preferably secured to the pipe by using a resilient sealing O ring 24 around the device. The device preferably includes a handle 28 for aiding removal. The device may include a ventilation pipe 54 to limit the effect of back pressure as water enters the restrictor. The restrictor may include a colour coded insert comprising the flow control aperture. The restrictor is preferably used in a blue roof, i.e. a roof which provides standing water storage by converting the roof into a flow attenuation tank and reduces flow thereby helping keep water on the roof.

Description

ROOF OUTLET FLOW RESTRICTOR

To encourage conservation of existing sewerage capacity, recent UK legislation provides that water companies may bill customers in accordance with the v&ume of water discharged to the public sewers. New constructions are not allowed to increase the rate of water discharge compared to the pre-existing site. These objectives may be met by reducing the amount of hard landscaping and to provide attenuation tanks for temporarily storing peak rainfall runoff and discharging it to a sewer or storm drain at a lower flow rate over a longer period of time. However ground level or underground storage space is not always available.

Here it may possible to use a fiat roof as an attenuation tank instead. This is known as a blue roof It is also known to provide a cap fitment for a roof outlet which creates a weir, causing water to accumu'ate on the roof for harvesting or for supply to a green roof Blue roofs or roofs providing standing water storage may be conveniently combined with green roofs, or with paving stabs on support pedestals, to provide a concealed water flow attenuation tank or water storage/harvesting facility on the roof.

The standing water which may be present following sustained rainfall on a blue roof is challenging to the roof watertightness, but building techniques are available e.g. through the use of suitable waterproofing materials. upstand detailing and good workmanship, to provide a long lasting, leak free, low maintenance blue roof A Hue roof may be laid to zero falls (substantially level) and so requires no screeding. The standing water may impose a dynamic load which is lower than the screeding weight saved, so that the structural strength of the blue roof need not be any greater than an equivalent conventional flat roof. The dynamic load from the stored water may in any case be within the capacity required for snow loading. The blue roof may be for example designed to safely carry a given maximum depth of water build-up. with overflow spouts to provide a fail-safe. The given maximum depth may be calculated to absorb the majority of expected weather events, e.g. all but a one in 10 year storm, while allowing an acceptably low peak flow rate through the building's rainwater drainage system.

Syphonic outlets have been proposed, intended to provide accurately controlled low flow rates from a blue roof into the building's rainwater drainage system. This reduces the size

I

and capacity of the downpipes required to carry away the water from the roof, compared to a conventional rainwater drainage system. However, many flat roofs are designed with a 60 year life. Making the number of outlets and the downpipe flow capacity the same as in a conventional flat roof design wou'd allow for possihie conversion of a blue roof back to a conventional roof within this timespan. without major disruption to the remainder of the building structure. But then a problem arises in that the flow through each outlet must be carefully controlled and restricted, in order to produce a blue roof with the desired water holding and maximum flow rate attenuation properties. Conventional roof outlets are incapable of providing such accurate water flow contr&, being instead designed simply to maximise rainwater discharge rates from the roof as far as is reasonably practicable.

Furthermore, to date, there has been no reliable means of converting a conventional fiat roof drainage system to provide a blue roof, without having substantially to overhaul or replace the entire system of downpipes through which the rainwater is led away from the roof.

The present invention provides a drainage flow restrictor for installation in a roof outlet so as to provide a predetermined reduced flow tate through the outlet at a given depth of water above the restrictor. thereby to form a blue roof. In this way, a pre-existing flat roof drainage system may be relatively easily converted to provide a blue roof, with desired attenuation of peak rainwater discharge rates. In many cases it will not be necessary to alter the pipework system or roof outlet positions, In some cases it may even be possible to re-use the existing roof outlets, either where the existing roof covering and falls are suitable to provide a blue roof, or where the roof covering can be upgraded using the existing outlets.

In the case of a new build installation, the blue roof and associated pipework can be designed for ready conversion back to a conventional roof while leaving the pipework substantially undisturbed.

Preferably the drainage flow restrictor is configured for fitment across a discharge spigot or discharge pipe of the roof outlet to reduce the available flow cross-section of the roof outlet.

For example the flow restrictor may comprise a flow control aperture of reduced cross-section compared to the discharge spigot or pipe. The flow restrictor may form a peripheral seal with the discharge spigot or pipe in use, and the flow control aperture may comprise a through-going passageway in the flow restrictor. A resilient seal may be used to retain the flow restrictor in the discharge spigot or pipe as a push fit. The flow restrictor may comprise a radial protrusion such as a flange. collar or one or more bosses, which in use co-operate with the shoulder formed at the junction of the roof outlet's discharge spigot or pipe and its main body or sump, to ocate the flow restrictor in the roof outlet. Preferably the radial protrusion is shaped so as to prevent retention of standing water under no-flow conditions, and hence avoid silt accumulation, e.g. the radial protrusion comprises a step-free collar.

Advantageously, the flow control aperture is provided in a removable insert received in a body portion of the drainage flow restrictor. In this way. the flow rate may be accuratdy controlled in accordance with design cakulations by selecting the insert from a set of standard inserts, each having an accurately formed, differently sized and/or shaped flow control aperture to provide a predetermined flow rate at a given depth of water above the drainage flow restrictor. The insert may be colour coded for easy recognition during initial fitment or if it needs to be replaced during maintenance of the roof outlet and flow restrictor.

The insert may be peripherally sealed to the body portion of the flow restrictor when received in it. A resilient seal may be used to retain the insert in the body portion as a push fit. The insert may be longer in the flow direction than the flow restrictor body portion, so that it can be easily removed from the flow restrictor body portion. The insert may comprise a radial protrusion such as a flange. collar or one or more bosses, which in use co-operate with a complementary seating in the flow restrictor body portion. The insert may comprise a drip feature which lies outwardly of the flow control aperture, so that the aperture remains substantially unobscured by any calcification or other mineral deposits occurnng over time.

The drip feature may comprise a continuous lip surrounding the flow control aperture. The flow restnctor is preferably coated with or formed from a hydrophobic material or matenals, so as to minimise calcification/mineral scale deposit formation. For example the flow restrictor body and insert may be injection moulded or machined from PVC or UHMW polyethylene, or may be coated with PTFE.

The flow restrictor may comprise a handle which extends upwardly in use, allowing the flow restrictor to be readily installed in the roof outlet andlor removed for inspection or maintenance.

The flow restrictor may be provided with an air vent which makes the flow rate through the flow control aperture substantially independent of downstream flow conditions/backpressure. The air vent may for example comprise a tube upstanding from the flow restrictor, with an upper end open to the atmosphere, at a level above the surface of the water accumulated on the blue roof in use. The upper end of the vent tube may extend along a central axis of the flow restrictor whereby it may conveniently project through a central aperture in a grating fitted to the roof outlet in which the flow restrictor is installed. The vent tube may be joined to the flow restrictor at a position offset from the central axis of the flow restrictor, for more convenient positioning of the flow control aperture, e.g. allowing it to extend centrally through the flow restrictor. The use of the grating (e.g. an otherwise conventional domical grate) helps to protect the flow restrictor and also preserves the relatively normal appearance of the roof outlet, as the flow restrictor is largely hidden beneath the grating. At least the projecting upper end of the vent tube is preferaNy protected by a preferably high visibility cover which provides a blunt end for safety against accidental impalement.

The invention and some of its preferred features and advantages are further described below by way of example with reference to illustrative embodiments shown in the drawings, in which: Figure 1 is a highly diagrammatic concept drawing of a first embodiment of a flow restrictor according to the present invention installed in a roof outlet tail pipe; Figure 2 is a highly diagrammatic concept drawing of a second embodiment of a flow restrictor according to the present invention installed in a roof outlet tail pipe; Figure 2a is a cross-sectional view of a flow restrictor generally corresponding to Figure 2, fitted with an insert providing a flow control aperture/passageway of large diameter; Figure 2b corresponds to Figure 2a, but shows a fitted insert providing a flow control aperture/passageway of medium diameter; Figure 2c colTesponds to Figure 2b, but shows a fitted insert providing a flow control aperture/passageway of smaller diameter; Figure 3 is a perspective view of a flow restrictor corresponding to Figure 2a, with the insert shown extracted from the flow restrictor body; Figure 4 shows the flow restrictor of Figure 3 assembled and installed in a roof outlet; Figure 5 sows a modified form of the flow restrictor body and vent tube shown in Figures 3 and 4, and Figure 6 is a highly diagrammatic concept drawing of a flow restrictor embodying the invention installed in a roof outlet in an illustrative combined blue roof and green roof.

As shown in Figure 1, the flow restrictor 10 has a main body 12 formed from PVC or a similar hydrophobic, low wettability materiaL The flow restrictor 10 is retained in position at the top end of a vertical spigot or tail pipe 14 forming the water discharge connection of a roof outlet 16. The main body 12 has a radially projecting collar 18 by which the flow restrictor 10 is suspended so as to depend into the spigot 14. The collar 18 is supported on the shoulder 20 formed by the junction of the spigot 14 and the lower part of the roof outlet sump 16. The lower surface of the collar 18 is angled to match the slope of the outlet sump.

whereas the upper surface of the shou'der 18 is downwardly and inwardly sloped so as to be continuous with a funnel shaped upper surface 22 of the how restrictor body 12. The collar therefore provides a step-free Up forming the junction between the outlet sump and the flow restrictor 10 so that there are no crevices for silt accumulation.

An 0-ring 24 is accommodated in a circumferential groove 26 around the outside of the main body 12, so as to form an annular seal with the interior wall of the spigot 14 when the flow restrictor 10 is installed in the roof outlet 16. The 0-ring also helps to retain the flow restrictor in the roof outlet spigot 14 as a frictional fit. The flow restrictor 10 has a handle 28 formed from colTosion resistant metal e.g. stainless steel tubing or bar bent into an inverted U-shape, to allow the flow restrictor 10 to be readily pushed into the spigot 14 or pulled out again for inspection and maintenance. The limbs of the handle have pinch points which form radially upset stops 30 engaging the flow restrictor body upper surface 22. The lower ends 32 of the handle limbs extend through the flow restrictor body 12 and are threaded so as to carry securing nuts 34, Tightening the nuts clamps the body 12 between the nuts 34 and the radially upset stops 30 to secure the handle to the body 12.

The main body 12 of the flow restrictor has a through-going cylindrical passageway 36 which forms a flow control aperture of reduced cross-section compared to the discharge spigot or pipe. The passageway 36 may be manufactured to a range of different diameters (e.g. differing in 5mm increments from one diameter to the next) as represented by the parallel dotted lines, as necessary to provide the required Urnited rainwater discharge flow rates with a par icular maximum head of water above the flow restrictor 10. The lower surface of the flow restrictor main body is provided with an annular, depending drip lip 38 surrounding the lower end of the cylindrical passageway 36 and having an inner suiface 40 sloping continuously downwardly and outwardly from the thwer end of the cylindrical passageway, such that any mineral deposit accumulating on the drip lip will not obstruct the cylindrical passageway and reduce the controlled water flow rate through it. Although shown as concentric with the main body 12, the axis of the cylindrical passageway 36 may be offset from the main body centra' axis.

The flow restnctor lO shown in Figure 2 is similar to that of Figure i, with the following main differences. The limbs of the handle 28 are cemented into blind-ended holes 33 in the main body 12 by a suitable adhesive. A centra' through bore 42 and couterbore 44 form a seating in the main body 12 for a separate. removaNe insert 46 in which the passageway 36 forming the flow control aperture is provided. The bore or counterbore is provided with a circumferential groove 48 for a second 0-ring 50 which frictionally retains the insert 46 in the seating 42, 44 and forms an annular watertight seal between the insert and main body.

Alternatively the 0-ring groove may be provided in corresponding positions around the outer circumference of the insert 46. A series of different inserts 46 can be provided, each with a cylindrical (or other shaped) passageway 36 of different standard diameter, so that the appropriate insert can be selected and installed in the main body 12 to provide a desired discharge flow rate for a given height of water above the flow restrictor 10/insert 46. The different inserts 46 may each be made from a different coloured plastic material, for easy identification. The insert bores 36 can be drilled/reamed out to a slightly larger diameter if necessary, for "fine tuning" of the restricted water flow rate. The insert 46 is longer than the bore 42/counterbore 44, so that the lower end of the insert with the drip lip 38 projects from the lower surface 52 of the main body 12. Pushing on this projecting end also allows the insert 46 to be removed from the main body 12 relatively easily when required.

The flow restrictor 10 is provided with an air vent 54 whereby water entering the flow control aperture 36 can displace air from the space in the pipework below, substantially independently of the flow conditionslbackpressure in the downstream pipework, so making the flow rate substantially independent of the downstream flow conditions, provided that the water flow rate at the restrictor is lower than in the downstream pipework. The air vent 54 comprises a passageway through the main body 12, parallel to the bore 42. The upper end of the passageway 54 is connected to a vent tube 56 whose upper end 58 extends above the maximum water level 60 on the blue roof.

Figures 2a, 2b and 2c show the main body 12 fitted with a brge bore 36a, medium bore 36b and smaller bore 36c insert 46a, 46b, 46c respectively. The 0-ring groove 48 is provided in the larger diameter upper end portion of the insert which is received in the counterbore 44.

The upper end of the tube 56 is fitted with a high visibility blunt safety cover 62 (Figure 2a).

Figure 3 shows the insert 46 removed from the bore 42/counterbore 44. Figure 4 shows the flow restrictor i2 with insert 46 fitted, both installed in a roof outlet 16. The roof outlet may be fitted with a domical grate (not shown) in the usual way. The vent tube 56 projects through a hole formed in the domical grate. In Figure 5, the vent tube 56 is bent so that its upper end 58 lies along the central axis of the flow restrictor 12. The hole in the domical grate may therefore be positioned at its centre, so that the vent tube does 56 not complicate the rotational alignment of the domical grate during fitment to the roof outlet 16.

Figure 6 schematically shows the outlet 16 and flow restrictor 12 installed in a combined green roof and blue roof. The outlet body 16 is supported on a structural deck 64 by a timber frame 66, surrounded by rigid insulation board 68 to form a warm roof. A waterproofing membrane 70 of suitable integrity for use with the standing water expected on a Hue roof is trimmed down into the outlet sump and sealingly secured by a clamp ring 72.

A protection and water retention mat 74 is installed on top of the membrane, with an aperture cut through above the outlet 16 to form an inspection chamber 76. Further similarly apertured layers are built up as follows: reservoir crate 78 (2 layers), filter sheet 80, soil and drainage matrix 82, planting media 84. The membrane 70 and reservoir crate 78 are led up the side of the retaining wall 86 as shown. A cover 88 for the inspection chamber 76 rests on the reservoir crate 78. The roof outlet spigot 14 is connected to a tail pipe 90 leading to the rainwater downpipes within the building.

Claims

CLAIMSI. A drainage flow restrictor for installation in a roof outlet so as to provide a predetermined reduced flow rate through the outlet at a given depth of water above the restrictor.
2. A drainage flow restrictor as defined in claim I, configured for fitment across a discharge spigot or discharge pipe of a roof outlet to reduce the available flow cross-section of the roof outlet.
3. A drainage flow restrictor as defined in claim 2 in which the flow restrictor comprises a flow control aperture of reduced cross-section compared to the flow cross-section of the discharge spigot or pipe.
4. A drainage flow restrictor as defined in claim 3 in which the flow control aperture comprises a through-going passageway in the flow restrictor.
5. A drainage flow restrictor as defined in claim 2, 3 or 4, which forms a periphera' seal with the discharge spigot or pipe in use.
6. A drainage flow restrictor as defined in any one of claims 2-5, in which a resilient seal is used to retain the flow restrictor in the discharge spigot or pipe as a push fit.
7. A drainage flow restrictor as defined in any one of claims 2-6, comprising a radial protrusion which in use co-operates with the shoulder formed at the junction of the roof outlet's discharge spigot or pipe and its main body or sump to ocate the flow restrictor in the roof outlet.
8. A drainage flow restrictor as defined in claim 7, in which the radial protrusion is shaped so as to prevent retention of standing water.
9. A drainage flow restrictor as defined in claim 7, in which the radia' protrusion comprises a collar providing a step-free junction with the outlet's discharge spigot or pipe.
10. A drainage flow restrictor as defined in claim 2 in which the flow restrictor comprises a removable insert having a flow control aperture.
11. A drainage flow restrictor as defined in claim 10 in which the insert is colour coded.
12. A drainage flow restrictor as defined in claim 10 or 11 in which the insert is peripherally sealed to a body portion of the flow restrictor when received in the flow restrictor.
13. A drainage flow restrictor as defined in claim 10 or 11 in which a resilient seal is used to retain the insert in a body portion of the flow restrictor as a push fit.
14. A drainage flow restrictor as defined in claim 12 or 13, in which the insert is longer in the flow direction than the flow restrictor body portion.
15. A drainage flow restrictor as defined in claim 10 or 11 in which the insert comprises a radial protrusion which in use co-operates with a complementary seating in a body portion of the flow restrictor.
16. A drainage flow restrictor as defined in any one of claims 10-15 in which the insert comprises a drip feature which lies outwardly of the flow control aperture.
17. A drainage flow restrictor as defined in claim 16 in which the drip feature comprises a continuous lip surrounding the flow control aperture.
18. A drainage flow restrictor as defined in any preceding claim, coated with or formed from a hydrophobic material or materials.
19. A drainage flow restrictor as defined in any preceding claim, comprising a handle which extends upwardly in use.
20. A drainage flow restrictor as defined in any preceding claim, comprising an air vent which makes the flow rate through the flow control aperture substantially independent of downstream flow conditions/backpressure.
21. A drainage flow restrictor as defined in claim 20, in which the air vent comprises a tube upstanding from the flow restrictor.
22. A drainage flow restrictor as defined in claim 21, in which an upper end of the tube opens to the atmosphere, at a level above the surface of the water accumulated on the blue roof in use.
23. A drainage flow restrictor as defined in claim 2i or 22, in which the upper end of the vent tube extends along a central axis of the flow restrictor.
24. A drainage flow restrictor as defined in any one of daims 21-23, in which the vent tube is joined to the flow restrictor at a position offset from the central axis of the flow restrictor.
25. A drainage flow restrictor as defined in any one of claims 2 1-24, in which at least the projecting upper end of the vent tube is protected by a cover which provides a blunt end.
26. A drainage flow restrictor as defined in claim 25, in which the cover is highly visible.