Building engineering
Water supply
Internal networks, pump stations and fire-water supply.
A building's water supply starts at the connection to the city main: the entry assembly, the water meter and, where the design calls for it, a storage tank. Inside the building the network divides — potable risers carry cold and hot water up to the fixtures on every floor, a separate main runs to the fire hydrants and the pump assembly, and gravity drainage takes waste water away. All three sit in the same building but work in different regimes: the potable network every day, the firefighting side waiting for years so that it can deliver its full flow in a single moment. That is why separating them is one of the first decisions in the design.
The critical point in the network is the furthest outlet on the top floor: that is where the pressure and the flow a fitting needs still have to be there, even while several outlets on the floors below are running at once. Pipe diameters, the duty and head of the booster set, its standby pump, the split into pressure zones by height and the pressure-reducing valves in the lower zone all follow from that one figure — enough water at the top, without excess pressure damaging the fittings at the bottom. Routing has to be agreed with ventilation, electrical work and the structure before slabs and shafts are closed; on the drainage side the falls and the vent stack do the same job, deciding whether the building later smells or gets noisy when a large volume comes down at once. A network sized too tightly shows it late: water hammer, swinging pressure, a pump cycling on and off, and a leak inside a wall that has already been finished.
Day to day, a water installation that was done properly is never noticed: the tap gives the same pressure morning and evening, hot water arrives straight away, the pump cannot be heard from the flats, and the pump station stays dry. The only parts that should stay visible are the ones that need servicing — isolating valves at the foot of every riser, the strainer, the check valve and the meter within reach, and rodding access along the drainage run. Alongside them sit the test and flushing records and the drawings any later repair will be worked from. Concealed pipework is the most expensive thing on a site to put right, so a day saved on calculation and testing comes back to the building as demolition.
What it covers
- Internal water supply network
- Fire pump stations
- Pressure calculation and pump selection
- Drainage networks
- System testing
Where it applies
- Multi-storey residential blocks
- Hotels and aparthotels
- Office buildings and business centres
- Shopping centres and supermarkets
- Clinics, universities and teaching buildings
- Plants, warehouses, underground car parks
Standards and regulations
The potable installation inside a building is described by the EN 806 series: how diameters are selected, which materials are admissible, and how the pipework is flushed and pressure-tested once installation is complete. EN 1717 sets where backflow protection is required, so that water from a technical or firefighting network cannot find its way back into the potable one. Falls, stack diameters and venting for gravity drainage inside the building are calculated to the EN 12056 series. On the firefighting side the pump assembly follows NFPA 20 for stationary fire pumps and hydrant and hose systems follow the EN 671 series, while EN 12845 governs the calculation wherever that pump station serves an automatic sprinkler network. Over all of it sit the building norms in force in Georgia and the technical regulation on fire safety, which set what water reserve and what pressure a given type of building requires.
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Frequently asked questions
What is the difference between potable and fire water supply?
The potable network is sized for everyday consumption, while the firefighting network is sized to deliver the flow and pressure the norm requires, for a defined duration, during a single event. That is why the two have different diameters, different materials and their own pump equipment, and why the norm requires them to be kept apart so that one cannot contaminate the other. Some sites also need a stored fire reserve, if the city network cannot supply the required flow.
Why is the water pressure weak on the upper floors?
Usually either the incoming pressure is not enough for the height of the building, or the riser diameter was chosen wrongly. The answer is not a bigger pump: it is a hydraulic calculation taken to the furthest outlet on the top floor, a split into pressure zones by height, a booster set with variable speed control, and pressure-reducing valves in the lower zone. Without that, the upper floors run short of water while excess pressure damages the fittings below.
Can a water supply system be reworked in a building already in use?
Yes, but the conditions are different: the routing has to fit the existing shafts or run exposed, the work is done in stages around a water shut-off schedule agreed in advance, and far more is demolished and reinstated. That is why work on an occupied site starts with a survey and an inspection of the existing network, so that it is clear what changes and what stays.
What determines the cost of a water supply system?
The main variable is the height of the building. While a building is low, the incoming pressure may turn out to be enough; as it gets taller, a booster set with a standby pump, variable speed control, a split into pressure zones and pressure-reducing valves in the lower zone all appear — and it is those assemblies, the plant space they need and their own power supply that move the cost estimate most. Added to that are the number of fixtures, how hot water is produced, the size of the firefighting section and the length of the pipework. How much each of them counts towards the cost is established by a survey: what pressure and flow the incoming main gives, where the pump assembly will fit, and what can stay from the existing network.
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