GB2067228A - Drainage systems in buildings - Google Patents

Abstract

A soil stack 1 of a building drainage system is provided above its highest inlet branch with a device such as a liquid trap 7 (through which air can bubble), or a one-way air valve (Figs. 2, 3 not shown), which device allows inflow of air into the top of the stack when there is a negative pressure in the stack, but prevents the outflow of foul air from the stack when the pressure in the stack is atmospheric or above. The use of the device prevents loss of water seal in appliance traps connected to the stack without the need for the stack pipe to project above roof level. <IMAGE>

Description

SPECIFICATION Improvements relating to soil systems This invention relates to soil systems, that is to say drainage systems for the disposal of soil effluent from domestic, commercial or industrial buildings.

Such soil systems have a soil stack into which sanitary appliances, i.e. sinks, wash basins and w.c. pans connect through branches which incorporate a water seal trap. The soil stack normally extends above the highest branch fitting to the open air. When an appliance discharges into the stack the water pouring into the stack from the appliance branch takes air with it and changes of pressure occur in the stack. Normally the pressure is negative immediately below the branch which is discharging and gradually becomes less negative over something like 80% to 90% of the distance to the outflow drain into which the lower end of the stack leads. Below this there is positive pressure increasing to a maximum at the bend at the base of the stack just upstream of the outlet drain.

In present day soil systems if the stack did not continue above the highest branch to open air, the negative pressure created by a discharging branch would suck out the contents of the water seal traps of the branches below the discharging branch so that after the discharge the appliances and hence the atmosphere of the building would no longer be isolated from the atmosphere of the outlet drain. The open end of the stack must by Regulation be 3 feet above any window which is within 10 feet horizontally of the stack and to achieve this normally involves passing the stack up through the roof of the building. This entails relatively high building costs and is also often unattractive from an architectural point of view.

The object of the present invention is to provide a soil system in which the need to pass the soil stack through the roof of a building is obviated.

According to the invention the soil stack is provided with a device at a position above the highest branch in the soil system which device allows ingress of air into the top of the stack when there is a negative pressure in the stack, but prevents the outlet of air from the stack when the pressure in the stack is atmospheric or above.

Such a device may take the form of a dne-way valve or a liquid trap.

The invention will now be further described with reference to Figures 1 to 3 of the accompanying drawings, which show in crosssection examples of devices as aforementioned fitted to the top of soil stacks.

Referring to Figure 1, the top of the soil stack is shown at 1. Fitted around the top of the stack is an annular member 2 which seals with the stack through '0' ring 3. The member 2 has inner and outer walls 4 and 5 and a central partition wall 6 which divides the channel shaped internal space of the member 2 into outer and inner limbs 7 and 8. The outer limb 8 is closed off at its upper end but is provided with port holes 9. In use the bottom of the channel shaped space of the member 2 is filled with a chemically stable liquid to a level above the lower edge of the partition wall 6, so that the device acts as a 'U' tube. Hence if a negative pressure exists in the stack 1 air will bubble through the liquid into the stack 1.

However, any positive pressure in the stack will never be sufficiently high for gases to bubble through the liquid from the stack into the atmosphere.

The top of the member 2 is provided with an upstanding rim over which is fitted a removable access cap 10.

Referring to Figure 2 the top of the soil stack is shown at 11 and a closure cap 12 is fitted to the top of the stack. At one side the closure cap is fitted with cylindrical valve chamber 13 which communicates through passage 14 with the interior of the stack. The chamber 13 is provided with a port in its bottom and onto the periphery of this port is snap-fitted a valve seating member 1 5 which has an annular triangular-sectioned rib 1 6 providing an upstanding valve seat. Located within the chamber 13 is a piston-like valve member 17 which normally rests under its own weight on the valve seat.The weight of the piston 1 7 is selected so that upon the occurrence of a negative pressure of about i" to 1 water gauge occurring in the stack the valve member 1 7 is lifted off the valve seat so that air ingresses into the stack from atmosphere, whereas gas-flow out of the stack into atmosphere will be prevented since the positive pressure within the stack required for this will force the valve member 1 7 on to the valve seat.

Referring now to Figure 3, the top of the stack is shown at 21. A cap member 22 is fitted on to the top of the stack 1 and has a central opening defined by a down-turned rim 23. Secured to this rim 23 by a clamping ring 24 is a length of lay flat plastics tubing 25 which extends into the stack 21. Due to the "memory" of the lay flat tubing, its lower end will normally remain closed.

However, if a negative pressure occurs in the stack 21, this will cause the lower end of the tubing 25 to open to allow ingress of air into the stack 21 through the opening in the cap member 22. Thus the lay-flat tubing 25 acts as a one-way, i.e. a nonreturn, valve.

A cover 26 is fitted onto the cap member 22 and is spaced from the cap member 22 to provide passages for the flow of air from atmosphere to the central opening in the cap member.

In modifications of the arrangement shown in Figure 1 , the port holes 9 may be shielded from above against the ingress of dust. Such a shield may take the form of a horizontal ledge extending from the cap 10 and formed integrally with the cap. Alternatively an angle sectioned ring may be secured to the top of the outer wall of the member 2 so that one of its limbs extends over the ports 9 at a distance above the ports 9. In a still further alternative form the shield may comprise a ring of arcuate cross-section secured along one of its edges to the top of the member 2 immediately above the partition wall 6, the other edge being located just outside and above the top of the outer wall of the member 2.

Claims (6)

1. A soil stack provided with a device at a position above its highest branch, which device allows ingress of air into the top of the stack when there is a negative pressure in the stack, but prevents the outflow of air from the stack when the pressure in the stack is atmospheric or above.

2. A soil stack according to claim 1 , wherein said device comprises a one-way valve.

3. A soil stack according to claim 2, wherein said one-way valve comprises a length of lay flat plastics tubing which is secured around the air inlet of the stack at one end and extends from said one end into the stack.

4. A soil stack according to claim 2, wherein the stack includes a cylindrical valve chamber through which air passes from atmosphere into the stack and a piston-like valve member is engageable under its own weight with a valve seating to close the valve chamber, the weight of the piston being so selected that upon a predetermined negative pressure occurring in the stack said valve member is automatically lifted off its seating to allow ingress of air into the stack.

5. A soil stack according to claim 1 , wherein said device comprises a liquid trap through which air passes from atmosphere into the stack.

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6. A soil stack substantially as hereinbefore described with reference to Figure 1 or Figure 2 or Figure 3 of the accompanying drawings.