Vented roof drain insert

An improved vented drain insert for insertion into a larger diameter drain pipe, preferably, a roof drain pipe. The insert has a tubular portion which extends into the drain pipe forming an annular restriction in the primary passageway through the drain pipe. A vent tube is provided to provide a secondary passageway from above the inlet to the drain past the annular restriction to the drain pipe below the drain insert. The vent tube is believed to be advantageously vent air and/or equalize pressures below the drain insert under flow conditions in the drain pipe in which air is present in the drain pipe.

SCOPE OF THE INVENTION 
This invention relates to roof drains and, more particularly, to vented 
roof drain inserts and to an improved configuration of a roof drain which 
provides for improved water flow. 
BACKGROUND OF THE INVENTION 
Roof drain inserts are known such as those taught by U.S. Pat. No. 
4,505,499 to Uglow et al, issued Mar. 19, 1985 and U.S. Pat. No. 4,799,713 
to Uglow, issued Jan. 24, 1989. Such roof drain inserts are particularly 
useful in situations where a roof is being resurfaced and a new roof drain 
is desired to be installed at a height above the existing roof drain. The 
roof drain inserts have an upper flange for securing to the new roof 
surface and a tubular member which extends coaxially down inside the 
existing drain pipe. Since the roof drain insert is received within the 
drain pipe the horizontal cross-sectional area through which water can 
flow is reduced in the insert as contrasted with that in the drain pipe. 
SUMMARY OF THE INVENTION 
The present inventor has appreciated that the restricted area for water 
flow through a roof drain insert can reduce the flow rate at which water 
can pass through the roof drain. Further, the inventor has appreciated the 
fact that the drain insert provides a flow path with a restricted area of 
flow through the insert which then opens into the full cross-sectional 
area of the drain pipe, can under some flow conditions, and particularly 
where air is present in the drain pipe or entrained in the water flow, 
result in reduced water flow due to the interaction of water and air. 
Accordingly, to at least partially overcome these disadvantages, the 
present invention provides a drain with a vent tube which provides a 
secondary pathway for communication from above a drain inlet to below a 
segment of the pipe of restricted cross-sectional area. 
An object of the present invention is to provide a novel vent tube for use 
in roof drains, an improved roof drain insert with a secondary vent 
passageway and a roof drain assembly incorporating a secondary vent 
passageway. 
Another object is to provide, in a roof drain assembly with an annular 
restriction to flow therethrough, a secondary vent passageway providing 
communication from above the drain inlet to below the annular restriction. 
Accordingly, in one aspect, the present invention provides in a drain 
assembly having a primary passageway for flow with an upper segment of 
reduced cross-sectional area opening into a lower segment of a greater 
cross-sectional area, a secondary passageway for flow extending from above 
an inlet to the primary passageway into the lower segment. The invention 
is particularly useful to assist fluid flow in the context of drains which 
are roof drains, however, can be advantageous in other drain environments 
where water may, under varying conditions, back up about a drain inlet and 
then flow downwardly through an area of restricted cross-sectional area 
before flowing into an area of increased cross-sectional area. 
In another aspect, the present invention provides a roof drain insert 
having a tubular portion with a lower outlet end adapted for securing 
within a large diameter cylindrical drain pipe, 
said tubular portion having an upper inlet end, 
an upper roof engaging sealing flange extending radially outwardly from 
about the upper inlet end of the tubular portion to prevent flow of water 
therethrough other than via the upper inlet end, 
an annular sealing ring disposed about the tubular portion proximate the 
lower outlet end to form a seal between the tubular portion and the drain 
pipe, 
an air vent tube secured to the insert extending coaxially within the 
insert from a tube inlet end upwardly above the upper inlet end of the 
tubular portion to a tube outlet end below the lower outlet end of the 
tubular portion. 
In a further aspect, a drain comprising 
a vertically extending primary drain passageway for flow of water 
vertically downwardly therethrough, 
an uppermost drain entrance opening opening into the primary passageway for 
igress of roof water therein, 
an annular restriction member disposed within the primary passageway 
blocking flow of water therethrough other than through a central vertical 
restriction segment of the primary passageway defined centrally within the 
annular restriction member, 
the primary passageway having a vertical exit segment immediately below the 
annular restriction member with the exit segment having an horizontal 
cross-sectional area greater than a horizontal cross-sectional area of the 
restriction segment and with the restriction segment opening directly into 
the exit segment at a juncture therebetween, 
a secondary passageway providing communication between an upper opening 
disposed at a height vertically above the drain entrance opening and a 
lower opening disposed within the primary passageway in the exit segment 
proximate the juncture between the restriction segment and the exit 
segment, 
the secondary passageway having a horizontal cross-sectional area for flow 
therethrough smaller than the cross-sectional area of the exit segment. 
The present invention provides an improved vented drain insert for 
insertion into a larger diameter drain pipe, preferably, a roof drain 
pipe. The insert has a tubular portion which extends into the drain pipe 
forming an annular restriction in the primary passageway through the drain 
pipe. A vent tube is provided to provide a secondary passageway from above 
the inlet to the drain past the annular restriction to the drain pipe 
below the drain insert. The vent tube is believed to be advantageously 
vent air and/or equalize pressures below the drain insert under flow 
conditions in the drain pipe in which air is present in the drain pipe.

DETAILED DESCRIPTION OF THE DRAWINGS 
Reference is made first to FIG. 2 which shows a vent tube member 100 in 
accordance with the present invention which vent tube member 100 is 
illustrated as used in FIGS. 1 and 3 in the context of providing an 
improved roof drain insert and an improved roof drain assembly in 
accordance with the present invention. The roof drain assembly illustrated 
in FIGS. 1 and 3 to 9, otherwise than in respect of the vent tube member 
100, is identical to that disclosed in U.S. Pat. No. 4,799,713 to Uglow, 
issued Jan. 24, 1989 and, therefor, FIGS. 4 to 9 which do not show the 
vent tube member 100 are prior art. 
FIG. 1 which shows a roof drain assembly in accordance with the present 
invention comprising roof drain insert member 10 including vent tube 
member 100, clamp ring member 12, straining basket 14, seal ring 16 and 
washer 18. 
The assembly is shown in FIG. 1 in the context of a roof generally 
indicated 20 supported by means not shown and below which a drain pipe 22 
is located also supported by means not shown. A thin water impermeable 
sheeting 23 covers roof 20. The roof drain insert member 10 is sealed to 
both sheeting 23 and drain pipe 22 and serves to transfer water collected 
on the roof to the drain pipe 22. 
Drain insert member 10 has a cylindrical tube portion generally indicated 
24 with an upper opening 26 at its upper end and a lower opening 27 at its 
lower end. Member 10 also has a thin, planar flange 28 extending radially 
outwardly about upper opening 26. 
The flange 28 is secured to the roof 20 by screws 30. Clamp ring member 12 
overlies flange 28 and is secured to flange 28 clamping sheeting 
therebetween by screw members 60 extending through socket forming members 
44 of the clamp ring member 12 to engage the post members 34 of the flange 
28. The straining basket 14 is removably secured in a snap fit on a rim 64 
of the clamp ring member 12. 
The cylindrical tube portion 24 of the drain insert member 10 extends 
downwardly through the upper open end 114 of the drain pipe 22 coaxially 
into the drain pipe 22. 
The lower end of tube portion 24 is sealed to drain pipe 22. While this may 
be accomplished in a number of ways, a preferred construction is shown in 
FIGS. 1 and 5 to 7 in accordance with the teaching of U.S. Pat. No. 
4,505,499 to Uglow et al, issued Mar. 19, 1985. 
Tube portion 24 is recessed inwardly about lower opening 27 so as to 
provide outwardly thereof an annular space 80 to receive about tube 
portion 24 annular seal ring 16 and washer 18 in axially sliding relation. 
Washer 18 has three enlarged radially inwardly extending lugs 82 each 
carrying metal nuts 84 secured therein. Three screws 86 extend from radial 
lugs 88 of tube portion 24 downward to engage nuts 84 and draw washer 18 
upwardly so as to compress seal ring 16 preferably of compressible, 
elastomeric (rubber) material. Ring 16 on being compressed is urged 
outwardly into sealing engagement with the inside wall 90 of drain pipe 22 
as well as axially into the recessed, radially inwardly extending annular 
shoulder 92 of tube portion 24. As shown, annular space 80 is only of a 
radial inward extent equal to the thickness of ring 16 except at three 
places where it is enlarged under lugs 88 as at 94 to accommodate lugs 82 
of washer 18. Lugs 88 present an upper flat surface which the head of 
screw 86 may engage between reinforcing flanges 96. Screws 86 are 
accessible through upper opening 26. 
The vent tube member 100 comprises a hollow cylindrical tube 102 with an 
open upper end 104 and an open lower end 106. 
The vent tube member 100 has two support arms 108 secured thereto carrying 
L-shaped washer-like members 110. As best seen in FIG. 1, the vent tube 
member 100 is secured to the roof drain insert member by the support arms 
108 spanning the opening 26 and having its members 110 secured by screw 
members 60 in opposing socket forming members 44 and post members 34. As 
seen, the tube 102 is located coaxially within both the drain pipe 22 and 
the tube portion 24 of the drain insert member 10. The upper end 104 of 
tube 102 is located at a height above the opening 26 in the drain insert 
member 10. The lower end 106 of tube 102 is located below the lower end 27 
of the tube portion 24. 
The assembly as shown in FIG. 1 provides, in effect, a primary flow 
passageway which extends from the opening 26 of the insert member 10 
through the tube portion 24 and out of the tube portion into the drain 
pipe 22. In this regard, the primary passageway may be seen to have 
segments of different horizontal cross-sectional area, namely, an entrance 
segment indicated as 116, a restriction segment indicated as 118 and an 
exit segment indicated as 120. 
The tubular portion 24, in effect, provides an annular restriction within 
the drain pipe 22 such that the horizontal cross-sectional area of the 
tubular portion, especially in the restriction segment 118, is less than 
the horizontal cross-sectional area of the drain pipe 22. 
The cross-sectional area of the primary passageway abruptly increases on 
moving downwardly from the restriction segment 118 into the exit segment 
120 as in the manner of a step increase at their juncture. 
The enlarged cross-sectional area in the exit segment 120 immediately below 
the annular restriction formed by the insert member 10 provides a location 
where under certain flow conditions, air may become entrapped in the 
primary passageway by water flowing down the drain. The tube 102 provides 
a secondary passageway 122 providing communication through the tube 102 
between the upper end 104 and lower end 106. The upper end 104 is disposed 
above the upper opening 26 to the primary passageway, such that under 
conditions of relatively high water flow, the upper end 104 is above the 
height of water which may back up on the roof. The lower end 106 is 
disposed below the restriction segment 118 in the exit segment 120 but, 
preferably, proximate the juncture between the restriction segment 118 and 
exit segment 120 to assist in providing communication to the exit segment 
120 proximate where the primary passageway widens into the exit segment 
120. 
Operation of the drain assembly with the vent tube member 100 is not fully 
understood. At low water flow rates, the vent tube member 106 is not 
believed to have any substantial effect on water flow as compared to an 
assembly without the vent tube member. As the water flow rate increases, 
conditions will be reached where air becomes entrapped in the exit segment 
120 and/or the entry segment 116 as by being within the drain pipe 22 
below the insert member 10 when the higher water flow commenced or by 
reason of being entrapped in downward flowing water and released into the 
exit segment 120. In a drain assembly without the vent tube member, the 
entrapped air can cause increased resistance to water flow through the 
drain pipe. However, in a drain assembly with the vent tube member, the 
vent tube provides the second passageway to equalize and/or relieve 
pressure differentials between the ends of the tube 100 as, for example, 
to vent air upwardly from the exit segment 120 immediately below the 
insert member 10 or to permit air to be drawn downwardly through the vent 
tube. As rain on the roof may accumulate in a heavy rain and the water 
level on the roof may rise with increased backlog, the vent tube can 
readily assist in equalizing pressures as by venting air while the upper 
end 104 is above the water level. By the time the water level may rise 
above the upper end 104 of the tube 102, the air venting is likely 
substantially complete so that with the water level above the upper end 
104, most of the air may be removed from the system and water may fill and 
flow down both the primary passageway and the secondary passageway. 
The preferred embodiment illustrated in FIG. 1 roughly approximates an 
assembly with a drain pipe 22 of an inside diameter of 3 inches for a 
cross-sectional area of about 7.1 sq. in.; an insert member 10 with a 
restriction segment 118 of a diameter of about 2.5 inches for an area of 
about 4.9 sq. in.; an entrance segment diameter of about 2.75 inches for 
an area of about 5.9 sq. in.; and a tube 100 of an external diameter of 
about 1/2 inches and an internal diameter of about 3/8 inches for an 
internal cross-sectional area of about 0.11 sq. in. Preferably, the area 
of the secondary passageway is substantially smaller than that of the 
primary passageway. Preferably, the cross-sectional area of the secondary 
passageway is less than 10%, preferably, less than 5% of the 
cross-sectional area of the drain pipe 22. 
Conventional roof drain pipes such as 22 most typically have an interior 
diameter in the range of about 3 to 6 inches. Typical roof drain inserts 
having annular sealing rings such as 10 may be expected to have diameters 
in their restriction segment of at least about one half inch less than the 
diameter of the drain pipe. For a 6 inch drain pipe, this represents about 
23% less cross-sectional area in the restriction segment than in the exit 
segment and, for a three inch drain pipe, this represents about 30% less 
cross-sectional area in the restriction segment than in the exit segment. 
The present invention is, therefore, preferable for use in drain 
assemblies in which the annular restriction represents at least about a 
15% reduction in the cross-sectional area of the drain pipe 22, more 
preferably, at least about a 23% reduction. 
In conventional drain pipes of about 6 inch to 3 inch diameters, vent tubes 
having various cross-sectional sizes can be used. Preferred vent tubes 
have an internal diameter in the range of 0.25 inches to 1 inch, more 
preferably, about 3/8" to 5/8". The cross-sectional area of the drain pipe 
22 is preferably about 30 to 100 times the internal cross-sectional area 
of the vent tube. 
FIGS. 1 to 3 show the vent tube 102 located coaxially centered within the 
drain insert member 10. This is not necessary. The vent tube 102 could be 
provided at other locations as, for example, adjacent one side wall of the 
drain insert member 10, possibly secured by but one screw 60 at its top. 
The secondary passageway could be provided integrally in the side wall of 
the drain insert member and could be provided inside and outside or in 
part inside and in part outside of the side wall of the drain insert 
member. 
The upper end 104 of the vent tube 100 in the preferred embodiment shown is 
located above the opening 26 by approximately between 20% to 100% of a 
diameter of the drain pipe 22 yet below the top of the straining basket 
24. 
The lower end 106 of the vent tube 100 is preferably located a distance 
below the end of the restriction segment 118 between about 20% to 100% of 
the diameter of the drain tube 22. 
The preferred vent tube 100 is shown secured in place, namely, by support 
arms 108. Additional support and/or locating devices could be provided as 
near the lower end 106 to keep the vent tube 100 in a desired location. It 
is preferred, however, that any support devices be minimized to not 
restrict water flow or flow of debris through the drain. 
Other features of the roof drain insert shown in FIGS. 4 to 9 are now 
discussed in more detail. Referring to FIG. 4, flange 28 has 
circumferentially spaced, counter-sunk holes 30 therein, through which 
recessed head screws 32 extend to secure flange 28 to roof 20 with a lower 
surface of flange 28 in locating abutment with an upper surface of roof 
20. 
Flange 28 carries six post members 34 which extend upwardly beyond upper 
surface 36 of flange 28. Each post member 34 is shown to be substantially 
cylindrical and to have a central aperture 38 which extends downwardly 
into post member 34. Central aperture 38 does not extend entirely through 
flange 28 but rather terminates as a blind end 40. 
Clamp ring member 12 overlies flange 28 such that a central opening 42 
through ring member 12 provides access to tubular portion 24 via upper 
opening 26. Substantial portions of ring member 12 are relatively thin and 
planar. 
Six socket forming members 44 are provided on ring member 12 each rising 
above the upper surface 46 of ring member 12. Socket forming members 44 
each define a socket recess 48 therein. Recess 48 has a lower opening 50 
in lower surface 52 of ring member 12. Socket forming members 44 
constitute a generally cylindrical upstanding wall 58 which at its upper 
end preferably extends radially inwardly to provide an inwardly extending 
flange 56 at the top of member 44. An entrance aperture extends downwardly 
through the top of each member 44 into socket recess 48. 
Socket forming members 44 are complementarily located having regard to the 
location of post members 34 so that each socket recess 48 may receive a 
post member 34 therein. 
Screw member 60 extends downwardly through the top of socket forming member 
44 via the entrance aperture and into central aperture 38 of a post member 
34 received inside socket recess 48. Screw member 60 engages post member 
34 to urge ring member 12 onto flange 28. Preferably, screw member 60 
carries a washer 62 to distribute loads onto socket forming member 44. 
With sheeting 23 located between flange 28 and ring member 12 
circumferentially about flange 38, sheeting 23 can be clamped between ring 
member 12 and flange 28 to form a seal entirely about the periphery of the 
drain assembly. 
Although not necessary, screws 32 fastening flange 28 to roof 20 may be 
located under sheeting 23 and flush with the upper surface of flange 28. 
Ring member 12 preferably is provided at its outer edge with a segmented 
rim 64 which extends vertically upwardly (axially) above upper surface 46 
of ring member 12 to where rim 64 has an enlarged radially outwardly 
extending flange-like lip 66. Rim 64 is shown as a plurality of 
circumferentially spaced segments, each designated 64 separated by 
vertical spaces or cut-out portions 70 extending downwardly to the height 
of upper surface 46 of ring member 12 as best seen in FIG. 4. When used in 
securing roof sheeting 23, spaces 70 permit water to pass through rim 64 
when the water rises merely to the height of upper surface 46 of the ring 
member. 
While FIGS. 1, 4 and 8 show use of a drain assembly in its preferred use 
with roof sheeting 23, the drain assembly can also be used with an asphalt 
type roof sealing system as shown in FIG. 9 in which a layer 72 of tar, 
asphalt or other sealant, preferably covered by gravel 74, may be poured 
directly over roof 20. In this case, ring member 12 is urged directly onto 
flange 28. Segmented rim 64 serves to help the asphalt or tar 72 and 
gravel 74 from entering the drain. 
In order to securely grip sheeting 23, as seen in FIG. 4, the lower surface 
52 of ring member 12 may have one or more downwardly extending angular 
ridges 98. Preferably, complementary located and sized grooves 99 may be 
provided in the upper surface 36 of flange 28, to assist in gripping sheet 
23 and also, as shown in FIG. 9 when no sheet is between the ring member 
12 and flange 28, to accommodate ridges 98. 
The drain assembly preferably has a straining basket 14 which prevents 
leaves, twigs, paper and the like from entering and clogging the drain. 
Basket 14 is shown to have a lower peripheral edge 75 with a downwardly 
extending inner projection 76 to closely contact the radially inside 
surface of rim 64. Preferably, three catch members 77 are provided on 
basket 14 as seen in FIG. 1. Catch members 77 engage under lip 66 to 
securely retain basket 14 onto ring member 12. With basket 14 having some 
resiliency, basket 14 may be snapped on and off of lip 66. 
Preferably, each of drain insert member 10, ring clamp member 12, straining 
basket 14 and washer 18 may be moulded from plastic as by injection 
moulding. The particular configuration of the post members permits 
moulding of the drain insert member with a two piece mould with the tube 
portion tapering a minor, insignificant amount downwardly. One piece of 
the mould may provide the upper and inside surfaces while the other peice 
of the mould may provide the lower and outer surfces of the tube portion 
24. 
Providing the post members and socket forming members to be upstanding 
about the upper surfaces of the flange and the clamp ring member is 
advantageous where asphalt, tar or other sealing materials are to be 
applied and frequently are to be slopped onto a drain, making location of 
screw holes difficult. 
With the post members having a blind end and effectively sealing the thread 
portion of screw member 60 therein, corrosion of the screw member can more 
easily be withdrawn after the passing of time, if necessary. 
In the preferred embodiment shown, the post members and socket forming 
members have been shown to be cylindrical. It is to be appreciated that 
many other complementary shapes could also be used. 
While the invention has been described with reference to preferred 
embodiments, the invention is not so limited. Many variations and 
modifications will now occur to those skilled in the art. For a definition 
of the invention, reference is made to the appended claims.