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08 Aug PA 250

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Katherine Towers stands tall and green

By Benjamin Brits | All images Plumbing Africa

Another towering commercial building is the latest addition to Sandton’s mixed use precinct.

Located within the new Katherine Street precinct is a development within walking distance of Sandton City and the Gautrain Station that will become the new head office for Bidvest Bank.

Katherine Towers offers expansive views of its surroundings and will become a prominent Sandton landmark. The building was designed without an underground basement parking structure and therefore has nine floors of above-ground parking, with 11 floors of office space catering for 1 000 parking bays and more than 23 000m² of lettable area.

The project was started mid-2017 and is expected to be completed in full at the end of July 2019.

Each of the bathrooms both male and female are equipped with electronic washbasin taps and soap dispensersEach of the bathrooms (both male and female), are equipped with electronic washbasin taps and soap dispensers. Image: Plumbing Africa

Project challenges

Time was a challenge as deadlines were tight from the start, so the wet services team had to push to get things done. However, this is the nature of a project of this size and all the teams knew what needed to be achieved from the start.

As the building was still under construction during the plumbing installation, access to get the material to the higher floors was limited and the lifts were not yet in operation, so the various teams had to rely on having to walk up and down staircases or scaffolding, and if they caught a break they would get to use the hoist system.

Small bore copper pipes were installed as well as large bore galvanised pipes. HDPE drainage and rainwater systems were also installed. Image: Plumbing Africa
Small bore copper pipes were installed as well as large bore galvanised pipes. HDPE drainage and rainwater systems were also installed. Image: Plumbing Africa
The hot water installation is circulated by means of a ring main that re-connects with the hot water storage vessels to ensure constant hot water supply. Image: Plumbing Africa
The hot water installation is circulated by means of a ring main that re-connects with the hot water storage vessels to ensure constant hot water supply. Image: Plumbing Africa

Project design specifications

The client brief and subsequent design in terms of the wet service was to develop a robust system that facilitated ease of maintenance and one that employed Green Star principles as a minimum, regardless of whether the building would go through the Green Star process when completed.

Although currently there is no rainwater harvesting or greywater reclamation in place, the design catered for a dual water reticulation system where these systems could be implemented at a later stage. One of the reticulation systems (with an alternative source such as water re-use) would be for flushing toilets and urinals, and the other dedicated to potable water use.

Consideration was also included for a ground water source such as a borehole, so in future if there is a decision to implement an alternative water source or water re-use, the infrastructure is already in place to support it through the installed plumbing system.

Challenges of meeting design specification

One thing that proves a common challenge in development like Katherine Towers is that when you are dealing with tenants, the tenant criteria can change all the time. What also happens is that you may have different tenants per floor which can further complicate the plumbing work required, or forward thinking about the plumbing.

Your start is always a base design and hopefully tweaking the design can accommodate a tenant’s specific requirements. There may be the need for special pause areas, kitchenettes, a bar, a gym, and so on, so it may become tricky to easily satisfy all of the needs.

The base design is always quite simple, but where the challenges start is when construction is ongoing and then a tenant is thrown into the mix that needs to be accommodated. You should always try to make your base design as flexible as possible so you can manage the changes or special request by identifying the most likely positions for these.

It does sometimes happen that you get get the odd request for a bar in the middle of nowhere and then the closest drain is 50m away and you need to come up with a solution. The sooner you get this information the better, making it more likely you’ll find a solution, because as the construction progresses, the constraints will just get tighter and tighter.

Starting a building from scratch, you can really do anything – you can put in additional stacks, an additional drainage or duct – but once the building has been started you have a structure that can become compromised and then special evaluation and permission will be required from the structural engineer on how and where to core. When you have brick work and partitioning that comes up, you have to sometimes be very creative because you may have a different office set-up on the lower floors, and so on.

The wet services system

The wet services of the building involve the water storage and pump system, the hot water generation, the domestic water installation, and the internal drainage installation.

The water storage and pump system comprise of a complete concrete potable water storage tank together with a Grundfos variable speed MPC pump set, the requisite diaphragm tanks, valves and fittings that supply pressurised water from the bottom of the building (being the lower parking floor at ground level).

The cold water pump set also pressurises the hot water generation plant that consists of two 5 000ℓ horizontal mild steel boilers, or calorifyers, coupled to air-to-water heat pumps. All of the copper piping, both supply and return to the plant room, forms the hot water installation.

The design concept is that under normal operating conditions the heat pump provides water at 55°C into the tanks and builds up hot water overnight that would be ready for use during the day. Should the heat pump fail, there are electrical back-up elements in the storage tanks that would turn on automatically on a false signal from the heat pumps.

The hot water is circulated throughout the building, up one of the ablution cores, and then turns on the topmost level and down the next ablution core, and then returns to the boiler. There is a ring of circulating hot water with no dead legs longer than 12m as per the requirements of the national standards.

The domestic cold water installation consists mainly of large bore galvanised steel piping, typically from 50mm to 100mm. Small bore cold water piping as well as all hot water piping was plumbed using copper.

A common noting or complaint from industry is that plumbers want to stay away from copper because of theft, but according to Leon Tobias of Jazzman Plumbing, “in all reality copper is still a cheaper option – even considering the theft element. The cost difference in fittings is vast between copper and plastic piping systems, even though the pipe is more or less the same price. When you look at big installations like this, copper lands up being highly competitive. Other companies may argue that plastic piping is better and faster to install, but for the plumbers on site chasing of the walls is still needed, you still have to install the pipe, still have to crimp the fittings and so on, so the time spent is not actually less.”

Says Trinesh Chanka of Izazi Consulting Engineers, “We chose copper for the installation because we went to tender on alternate piping solutions, and what we found is that the overall cost to the client at the end of the day is still more expensive for the alternate piping solutions. You will get a lot of stories from a lot of suppliers telling you that alternatives are cheaper, but then you start investigating as we did, and the result is that on a project such as Katherine Towers, the entire system is cheaper in copper, and this needs to be factored in for the client at the end of the day because everything is price sensitive these days.”

Security on site is obviously important and should definitely be an element where no corners are cut.

All of the waste lines installed are the Valsir HDPE system and the rainwater system installed is the Valsir Rainplus system. Rainplus was selected because it was also a cheaper overall solution and because the systems are interchangeable, it was just easier to run with. In terms of the HDPE drainage system, it was selected simply because it is a more robust system than PVC and its longevity is superior. You also don’t have the risk of the issue of glue coming undone in a couple of years.

The drainage installation from the core toilet and ablutions facilities.
The drainage installation from the core toilet and ablutions facilities.

 
Each floor holds easily accessible ducts for maintenance and inspections.
Each floor holds easily accessible ducts for maintenance and inspections.
 
The main kitchens were also part of the installation and comprise various stainless steel wash-up sinks and drainage.
The main kitchens were also part of the installation and comprise various stainless steel wash-up sinks and drainage.
 

Product choices

Jazzman Plumbing contributed to the choices of sanitary and brassware, which specified the same products as the Sasol Head Office, which is two buildings down. The choice of products were based on an overall experience with the brands, that are reliable and available.

One particular thing about choosing copper and galvanised pipework was that for a maintenance service, this is readily available from any plumber, and you also don’t need any specialised fittings or tools to weld the piping, which is one of the advantages of using a standard copper or galvanised system. Also, if a leak is sprung at midnight, the chances of you finding someone who deals with copper or galvanised is much more likely than with any specialised pipe system.

Impact on efficiency and sustainability

The Katherine Towers project is on par with the Green Star rating system for water usage guidelines. There are low-flow fittings installed on all units, so all of the basins, taps, and WCs are low flow.

“One thing that proves a common challenge in development like Katherine Towers is that when you are dealing with tenants, the tenant criteria can change all the time.”

Unique system elements

One of the things that was initially a worry for the wet services team was the fact that building was 20 storeys high and the plant room was on the ground floor. If you have to estimate on a 20-storey building with each floor being 3.5m high, this equates to 70m tall, which then requires a 700kPa line pressure before you even start thinking about friction losses and residual pressure for your fittings. So essentially you require 700kPa to get the water to the top of the building. This meant that the hot water boilers also needed to withstand a 700kpa pressure. The hot water boilers supplied by SA Heat Pump, are rated at 950kPa, which is a greater requirement than the norm, which is around 600kPa, and so these units operate nominally at 950kPa and have been tested to 1 500kPa.

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Valsir


 


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