High-rise drainage explained
The Akatherm drainage systems for high-rise buildings use only a single stack with the Akavent aerators. An Akavent aerator fitting breaks the fall on each floor, thus reducing the speed. As a consequence the vent pipe is obsolete and the pressure difference stays well within the limit of 3 mbar.
The unique shape of the fitting increases the capacity of the stack. The soil and waste flow from the higher floors smoothly converges with the flow of the lower floor. Push-fit sockets can be used for floor connections and also create the possibily to make a transition to other materials. The unique snap-sockets available in Akatherm HDPE even create a pull-tight connection.
The Akavent principle: Akavent installation movie for Akatherm HDPE:
- Akavent system design
An Akatherm soil & waste system for high-rise doesn't have any height restrictions: the dimensions are only determined by the number and types of drain fixtures that are connected to it. The Akavent system is preferably always equipped with one Akavent for each floor.
Follow the guidelines in this chapter in order to design the Akavent system for high-rise. Detailed calculations and examples of such designs can be found in the download area.
The basic Akavent system for high-rise consists of the following elements:
- Akavent branch on every floor
- A down pipe with Akatherm pipes and fittings
- A vent pipe through the roof of the same diameter as the down pipe
- A vent pipe on the first floor
Akavent branch in the down pipe
An Akavent down pipe branch fitting must be installed on each storey with a waste water connection. When the distance between two Akavent down pipe branches is larger than 6 m, a double offset must be placed in the down pipe (see illustration).
Zone division for each Akavent down pipe
If the building design requires more than one down pipe or the maximum capacity of a single down pipe will be exceeded, the storeys must then be divided into zones, each draining into different Akavent down pipes.
Deflecting the Akavent down pipe
The axis of an Akavent down pipe can be deflected without use of an equalisation pipe if the transition is constructed as shown in the illustration at the right. The angle of the offset must be 45° or less and the length of the offset pipe shorter than 1,5 m. No joint can be installed closer than 0,5 m above the offset and 1,0 beneath it.
If the axis of the Akavent down pipe can't be deflected in accordance with the illustration here above, the offset must be equipped with an equalisation line, to be designed in accordance with the illustration at the right.
If collectors have to be connected at this point, these connections can be made on the equalisation pipe, which is also called a diverter. There are also joint-free zones on the diverter pipe as indicated in the illustration at the right. The equalisation or diverter pipe must have the same diameter as the down pipe.
The maximum length for an unvented floor connector (or collector pipe) is 4 m at an incline of at least 1,0% (1:100) with no more than three 90° bends. The floor connector must be sized in accordance to national standards and guidelines.
Floor connectors that exceed these limits must have connections to the down pipe involving secondary pressure-relief pipes (vents). The joint of the relief pipe to the down pipe must be slanted downward at 45°, as shown in the illustration at the right.
Connectors are pipes that link a single drain fixture to the floor connector. According to EN 12056-2, the maximum length of an unvented connector is 3,5 m (without any specification of slope or number of 90° bends). If the 3,5 m is exceeded, the connector must be provided with secondary pressure relief as illustrated inthe illustration at the right.
All toilets must be connected to the Akavent down pipe branch using a 110 mm pipe. Directly opposing connections on the Akavent are not permitted.
Details about maximum total and per-storey drainage flows that may be handled by an Akavent down pipe can be found in our Specification Manual, paragraph 1.2.7 'Akavent system calculation'.
End of the Akavent down pipe
At the bottom of the Akavent down pipe, there must be an equalisation line in order to release all the built-up pressure. Fixtures can be attached to the equalisation line outside the joint-free zones. This equalisation pipe must be designed in accordance with the illustration at the right.
Venting the Akavent down pipe
The diameter of the down pipe must remain the same without reduction until roof level is cleared. Exceptions to this rule involve the construction of multiple down pipes with a combined pressure-relief pipe. The pressure-relief pipes may be joined together beyond a point 1 m above the highest joint. For the Akavent system, this is only permitted if the internal surface area of the combined pressure-relief line is equal to or larger than the sum of the internal surface areas of the individual pressure-relief lines.
The maximum number of combined down pipes is 8 x 110 mm or 3 x 160 mm, as long as the combined pressure-relief pipe has a diameter as specified in the table. The illustration at the right provides an example of 4 down pipes ø 110 mm with combined vent pipes.
The flow opening must be at least equal to the surface area of the connected pressure-relief pipe. The position of the opening for the roof duct on the roof must be designed in accordance with national standards and guidelines, so that moisture and waste material is not allowed to enter.
From down pipe to underground pipe
One or more down pipes may be connected to an underground pipe provided that the capacity of the underground pipe is great enough. The maximum capacity of an underground pipe is described in EN 12056-2, and depends on the diameter and incline. The total drainage flow is the simultaneous flow from all connected drain fixtures. The relevant calculation for an underground pipe will be performed in our Specification Manual, paragraph 1.2.7.
- Akavent fixing system and floor connections
For fixing the Akatherm soil and waste system for high-rise to the building structure the standard guidelines for fixing apply. The Akavent aerator needs to be fixed to the building on the top and bottom with an anchor bracket.
HDPE connection to Akavent branch
The connection to the Akavent can best be performed using Akatherm snap sockets. This unique push-fit socket joint with additional snap ring has the following advantages:
- Firm tensile joint if a snap groove exists in the pipe to be connected.
- The pipe is centred in the seal, offsetting any extra load on this seal as a result of the weight of the pipe.
- Prevention of any soiling of the seal due to 'scraping' it over the pipe.
A top joint can best be accomplished with an expansion socket in order to compensate for any
expansion of the down pipe (see illustration at the left). A side joint is made using the standard snap socket (see illustration at the right).
- Akavent duct size
The minimal duct size that is needed for an Akavent system can be found in the table below. The branch possibilities 1 and 3 are not to be used simultaneously for connecting soil and waste systems (see illustration at the right).