Method and device for reducing the risk of freezing of surface-water pipe-line systems

A method for reducing the risk of freezing of surface-water pipe-line systems of the kind comprising a plurality of drains and other inlets, such as rain-water drains, manholes and inlets from terrace and roof guttering, etc. Means are provided which prevent or reduce air currents in at least one of the drains and other inlets through which the flow of air would otherwise be excessive. The means is designed to permit water to flow therethrough without appreciable gathering of water therein.

The present invention relates to a method and a device for reducing the 
risk of freezing of surface-water pipe-line systems which include a 
plurality of drains and other inlets, such as street drains, menholes, 
inlets from terrace and roof gutters, etc. 
In regions of extreme cold the rain-water drains often freeze, resulting in 
great expense in thawing of the drains, and creating difficulties and 
costs as a result of flooding due, for example, to the melting of large 
quantities of snow. Freezing does not only occur in the actual intake of 
the drain, but also lower down in the pipe at a level which is normally 
considered free from frost. Various methods have been tried in an attempt 
to facilitate thawing of frozen pipes, one method being to provide the 
pipes with electric heating cables. This does not solve the basic problem 
of freezing, however, but merely simplifies thawing of the pipes when they 
are frozen. 
The present invention is based on research in the causes of such freezing 
problems, and to provide means for eliminating or reducing these causes. 
The present invention is based on the knowledge that a surface-water 
pipe-line system is normally so dimensioned that only a minor part of the 
total capacity is utilised under normal conditions. Drains and pipes 
forming part of a pipe-line system form a communicating system which 
permits air to pass freely between the various open connecting locations 
of the system. Large volumes of air can be carried in such a system, among 
other things because different drains lie at different levels. Moreover, 
certain inlets, for example terrace and roof gutters, can be connected to 
the system via drainpipes incorporated in heated buildings. At low ambient 
temperatures, for example, this gives rise to a marked chimney effect, 
causing cold air to be drawn into the system through the lowermost drains 
and to pass out through the highest drains. Strong air currents are also 
created by the pressure differences during a strong wind between the 
drains located on the windward side and those located on the leeward side 
of, for example, a large building. 
During the wintertime, these air currents cause large volumes of very cold 
ground air to be drawn down into the pipe-line system, causing drains and 
adjacent pipe networks to quickly freeze-up, even at levels which are 
normally considered frost free, resulting in ice plugs, frost lift and 
other damage. 
Thus, the invention is based on the understanding that freezing of 
surface-water systems is caused to a large extent by the cold ambient air 
drawn down into the system as a result of the strong air currents liable 
to occur in the system, as explained in the aforegoing. The problems 
created by air-flows through the pipe system could be solved by using 
known surface-water drains provided with water seals or traps, said seals 
either being incorporated in the drain or separate therefrom. In those 
regions which experience the problem of freezing according to the 
aforegoing it is not possible, however, to utilise a water seal or the 
like, since the seal would freeze. 
As previously mentioned, a surface-water pipeline system must be 
excessively dimensioned relative to the normal quantities of surface 
water, and in principle constitute a communicating system within a 
restricted take-up area. Consequently, it is not possible to cut-off the 
airflow completely without endangering the function of the system. 
The solution afforded by the present invention restricts the freedom to 
which the air can move freely in the pipe-line system to values which can 
be accepted in relation to the climate, without encroaching on the 
requirement for full water transportation 
Accordingly, the invention is characterized by arranging means for 
preventing or reducing the flow of air in at least one of the drains and 
other inlets through which the flow of air would otherwise be excessive, 
said means being arranged so as to permit water to flow therethrough 
without any appreciable gathering of the water. 
A preferred embodiment is characterized in that said means includes a 
spring-biassed air seal or trap arranged in the upper end of a respective 
drain or other inlet. The air seal may comprise a funnel-shaped sleeve of 
flexible, substantially gas-impermeable material, the lower end of which 
sleeve is normally held sealed by means of at least one spring so mounted 
that it attempts to flatten the lower opening of the sleeve by stretching. 
The spring preferably comprises a leaf spring attached at its ends to the 
lower edge of the sleeve. If so desired, the lower end of the sleeve may 
be cut obliquely, to enable draining of small quantities of water. 
In an alternative embodiment, the air seal includes at least two rubber 
lips which resiliently abut each other. In this respect, the air seal may 
include a central, cupola-like rubber shell and a surrounding, rubber lip 
arranged to lie against the lower edge portion of the cupola.

FIG. 1 illustrates the upper part 1 of a rainwater drain. Arranged on the 
upper part 1 of the drain are two raising and adjusting rings 2, and a 
cover 3 provided with a grating or grid 4. Arranged adjacent the upper 
edge of the part 1 of the drain is a means 5 which in the illustrated 
embodiment comprises a two-directional air seal or lock, through which 
water can pass down into the drain without gathering in the air seal. 
Thus, the air seal 5 is intended to prevent strong currents of air from 
passing down into the drain from the surroundings and also from passing up 
through the drain and out into atmosphere. The direction in which the air 
flows through the drain can namely vary in dependence on the ambient 
pressure conditions and also in dependence on the level at which the drain 
is located, i.e. if the location of the drain is one of the lower or 
higher locations of the system. Thus, the same air seal can be used both 
with rain-water drains located at low levels and intake drains connected 
to drainpipes incorporated in buildings and intended to carry away 
rainwater from roofs, terraces and the like. The site at which the air 
seal is located is selected so that said seal lies on a level in the drain 
where freezing would not normally occur because water flowing through the 
pipes connected to the drain maintains said location at a temperature 
somewhat above freezing. 
As will best be seen from FIGS. 2 and 3, the air seal comprises a 
funnel-like bag or sleeve 5 of flexible, substantially gas-impermeable 
material. A leaf spring 6 having a length which substantially corresponds 
to half the circumference of the lower, narrow end of the sleeve is held 
at its end to the lower edge of the sleeve 5. The spring 6 slideably 
extends through a holder 7. In its normal position, the spring 6 attempts 
to flatten out the lower opening of the sleeve 5 by stretching, so as to 
close said opening, as shown in FIG. 2. In this position the passage of 
strong air currents through the drain in both directions is prevented. 
In the event of rain or large amounts of water due to snow melting, the 
sleeve 5 will be opened to its fullest extent by the force exerted by the 
water flowing down thereinto, as illustrated in FIG. 3. The strength of 
the spring 6 can be selected so that even a relatively small amount of 
water is able to open the sleeve, said sleeve thus remaining substantially 
fully open until the flow of water to the sleeve ceases, at which time the 
spring 6 will return to the state illustrated in FIG. 2 and close the 
sleeve. The funnel-like shape of the sleeve 5 has been chosen so that the 
lower end of the air seal can be closed, in the manner shown in FIG. 2, 
without coming into contact with the walls of the drain 1. The air seal 
may also be of conical configuration over solely a part of its length and 
of circular-cylindrical configuration over the remainder of its length. 
In the aforedescribed embodiment only one single leaf spring 6 is required, 
said spring being completely protected from the water flowing through the 
drain, thereby rendering the device extremely reliable in operation and 
minimising the need for maintenance. As will be understood, if necessary a 
corresponding spring can also be arranged around the other half of the 
sleeve. The effect obtained with the leaf spring 6 can also be obtained 
with coil springs, by arranging the springs so that they attempt to 
flatten out the lower end of the sleeve by stretching. The use of a leaf 
spring to effect the closing and opening of the seal is more expedient, 
however, since the leaf spring tends to switch rapidly between the states 
illustrated in FIGS. 2 and 3. 
Thus, an air seal according to the aforegoing fulfills its function of 
preventing undesirable air currents through the drain while not 
encroaching on the ability of the drain to allow water to pass 
therethrough and while not allowing large quantities of water to collect, 
which might freeze. The water seal can also be readily installed in 
existing drains and may be suspended, for example, from a flange clamped 
between two drain sections. The level at which the air seal is placed can 
be selected, inter alia, with view to the risk of freezing and with view 
to the requirement of access. 
FIG. 4 illustrates an alternative embodiment of the air seal illustrated in 
FIGS. 1-3, the lower end of the funnel-shape sleeve being cut obliquely. 
When only a small amount of water flows down into the drain, this 
embodiment of the seal enables the water to seep therethrough, optionally 
through a small opening obtained adjacent the lower edge of the otherwise 
closed opening. This avoids the necessity of opening the air seal 
completely solely for the passage of small quantities of water. As will be 
understood, a fully open sleeve without the opening being substantially 
filled by the water passing therethrough would enable those air currents 
which are to be prevented according to the invention to pass through the 
drain. 
FIG. 5 illustrates an air seal according to the invention arranged in the 
inlet pipe 8 of a collecting drain or main drain 9, from which incoming 
water flows out through a collecting line 10. The air seal 5 is 
principally of the same design as the air seal shown in FIGS. 1-3, 
although in this embodiment the seal is provided with a straight edge 11 
for preventing undesirable damming of water in the line 8. 
The flexible sleeves of the air seals illustrated in FIGS. 1-5 are suitably 
made of a woven glass-fibre or polyester material coated with silicon or 
Teflon for preventing snow and ice fastening to the sleeve. 
FIG. 6 illustrates an alternative embodiment of an air seal according to 
the invention, intended to be positioned immediately beneath the grating 
12 of rainwater drains. In this case, it is not pssible to avoid the risk 
of the actual air seal freezing during the wintertime. Consequently, the 
air seal has been designed to permit freezing and to facilitate thawing. 
The air seal is also so designed that if, for example, a stone falls down 
into the drain the seal will only open locally, thereby to avoid 
unnecessary air currents through the drain. 
The air seal illustrated in FIG. 6 comprises a central, cupola-like shell 
13 made of a suitable rubber material, and an outwardly lying, arched 
collar-like body 14 made of a corresponding grade of rubber. Thus, the 
bodies 13 and 14 together form two mutually abutting lips, which prevent 
air from flowing in either direction, but which can be opened to permit 
water to flow down through the drain. A suitable rubber material for the 
air seal shown in FIG. 6 is, for example, butyl rubber, on which ice and 
snow will not fasten. 
The embodiment illustrated in FIG. 6 can also be used with rectangular 
drains. In this case, the rubber elements have the form of linear rubber 
strips arranged to resiliently abut each other along their longitudinal 
edges. 
All of the air seals described above are constructed so that hoses of large 
diameter can be passed down therethrough, for sludge-removing or thawing 
purposes. The seals, however, effectively prevent the passage of 
undesirable airstreams and are designed so that they can be fitted to 
drains of various shapes by means of different attachment devices. Air 
seals according to the invention can be placed directly in the gratings of 
drains or at a desired level therebeneath and may also be combined, for 
example, with existing so-called sand traps. The design of the air seal 
itself can, however, be varied in several respects within the scope of the 
claims.