Water and sewerage challenges for major hotels
Architects today are creating some unusual building designs in order to capture the imagination of their clients and the attention of the public.
The initial concept of many of these buildings can present unique challenges to the plumbing engineering design, which is required to ensure function follows form.
One of the aims of World Plumbing Review is to provide readers with an inside view of a collection of the most interesting and challenging projects from around the world as we talk to the engineers who are tasked with making these buildings ‘work’.
In the Brazilian city of Sao Paulo, a spectacular example of upmarket boutique accommodation designed by Brazil’s Ruy Ohtake forms an inverted arc flat on top and supported at each end by concrete pillars 82 feet (25m) high.
The 215,000 square feet (20,000m²) constructed area of the appropriately named Hotel Unique (otherwise known as the Watermelon Hotel) consists of six floors, 95 rooms, two restaurants, pools and a gymnastics academy. On the roof is a presidential suite complete with gymnasium and garden, as well as the Sao Paulo Sky restaurant and a swimming pool.
A full floor – which covers 54,000 square feet (5000m²) and is almost 20 feet (6m) high – is designed for events, conferences and exhibitions, and it can accommodate 1200 people.
Of the 95 rooms, only four are on the narrow first floor, and the top floor has 30 rooms that benefit from sweeping city views. Rooms at the end of corridors on each level feature a wooden floor that curves into the wall to take account of the outer arc.
All hydraulic and mechanical services for Hotel Unique were designed by the Sao Paulo consultancy MHA Engineering. MHA civil engineer Marcia Brandao Da Silva says that from the outset there was a strong focus on utilising the most modern technology and maximising clientele comfort.
“The aim was to construct a hotel that is different and could become a ‘postcard’ for Sao Paulo, not only for its facade but also for its infrastructure,” she says.
“The water reticulation system utilises PEX flexible polyethylene pipe connected to a manifold that is connected to cold and hot water risers in the central services shaft. This PEX system is very advantageous from a labor point of view because the material is light and can be easily transported and installed.
“Water is distributed directly to consumption points without intermediate connections, and all tubing passes inside a dry wall to facilitate maintenance without damaging the masonry. The whole plumbing system was pressurised about 2kgf/cm² (28.4psi), and the fire protection system was also pressurised and supplied from the same tank reservoir that is used for consumption. Due to the ceiling height, side-wall sprinklers were selected instead of a standard ceiling system.”
Water to feed the 4230 cubic feet (120m3) sprinkler system and similar capacity fire hose system is stored in the hotel’s 12,700 cubic feet (360m3) reservoir. Both systems use two kinds of pumps: jockey pumps to maintain the pressure at the wet standpipes, and fire pumps to provide pressure in the system when it drops below a preselected value.
“In Brazil there are codes relating to the design and installation of these systems,” Da Silva says.
“All drawings must go to the Fire Department for approval before installation proceeds. When installation is completed, the Fire Department carries out an inspection of the building.”
Hot water is provided by two operational gas heat exchangers in a manifold format, and a third heat exchanger is held in reserve. Recirculation pumps enable the water to be maintained at the required temperature at outlets.
The mains water supply is supplemented from an artesian well underneath Hotel Unique. This water is filtered regardless of its final destination and is from the same source that supplies Parque Ibirapuera’s lake.
“Water is pumped from the artesian well to the reservoir to assist in servicing all consumption requirements of the hotel. Extensive tests have shown that the artesian water is of excellent quality and a filter is only installed on the line to remove any possible solid material. The Brazilian health code requires water quality tests to be carried out every month.
“Water conservation was an important consideration when the architect specified the fixtures. For example, toilet cisterns have a maximum flush capacity of 1.6 US gallons (6L) and the air-conditioning system is also designed to save water. In addition, the recirculating hot water system provides water at a good temperature in a few seconds. A major challenge was to design a system that ensured all the showers worked simultaneously at the same temperature and pressure.”
Design of the hotel’s sewerage system was also a challenge because of the many interfering structural elements of the building. A detailed interference study was done due to the ceiling height, and all risers were deviated to the sides to allow for the unusual architecture of the building. Sewage is sent to the basement, where it is connected to the public network. All wastewater discharge goes directly to the authority sewerage system with one exception: wastewater from the kitchen proceeds via a box to remove the grease.
Subsoil drainage, with local grated drainage in the pedestrian areas, caters for the rooftop garden areas of the presidential suite and the Sky restaurant. Collection and disposal of the run-off water from the garden and any excess rainwater around the local area is via a series of gravity system downpipe stacks in the central core down to ground level.
“One floor below the rooftop there is a technical floor, which includes a junction of the pipes in a shaft nearest the central elevators,” Da Silva says.
“Eight 150mm cast-iron pipes go down to connect with PVC pipes in the basement.
“Over-splash water from the rooftop pool is collected in grated outlets, then treated and put back into the pool recycling system via pumps and filters. Backwash wastewater from the pool treatment system discharges into the building’s sewerage system.”
Water supply for the rooftop plant and equipment is pumped up to provide suitable pressure. At the hotel there is one 12,700 cubic feet (360m3) reservoir from where the water is pumped to a secondary 2825 cubic feet (80m3) reservoir, then distribution occurs by gravity. At the technical floor there is a pump to increase the pressure at the roof, and separate pumps to service the swimming pool.
“A key factor in dealing with the challenges of this unusual project was the weekly meeting between the architects, engineers and builder,” Da Silva says. “This enabled any difficulties to be discussed and the best solutions to be adopted.”
Established in 1975, MHA Engineering provides specialised engineering consulting services for the public and private sectors in Brazil and internationally. The company has completed about 2000 projects covering more than 4200 acres (1700ha) of civil works, plumbing, fire protection, mechanical, HVAC and electrical installations. Services include systems design, management and supervision of construction, and preparation of structural calculations for challenging architectural projects including hospitals, shopping centres, industrial complexes and hotels.