1. DESIGN CONCEPT
Automated rain water system that helps to reduce drinking water usage in urban environments
Urban environment: schools (K-12), universities, hospitals, health care facilities, industrial factories, warehouses, shopping malls and apartment complexes.
Main enviroment challanges:
� High drinking water usage
� Very little outdoor space (mostly there is no free space)
� Strict construction rules, bureaucracy in construction terms and polices
Solution: Private rain water supply system that can be completly installed in the building
Rain water application in urban environment
Private rain water purifying technical solution for drinking purpose is complicated, very expensive, very high maintainance and operating costs, strict regulations and high health risks. Rain water is too dirty to be used as solvent in chemistry and construction material mixes (e.g concrete).
Conclusion: Private rain water purification solution in drinking and purposes is OUT. Rain water can�t be used in chemistry or construction with high standards.
Rain water application:
- Toilet flush (with antibacteria products)
- Fire sprinklers
- Low hygiene pressaure washers
2. SYSTEM DESIGN
The system must have following operating assemblies:
� Roof draining system (canals and pipes) to collect and direct tthe rain water into reservuar (s)
� Rain water reservuar (s) for storing the water
� Reservuar ventilation
� Option to drain the overflow water into sewer / second reservuar
� Pumps for circulating the water
� Valves to control the circulation
� Monitoring and control devices
� Piping network
� The system must have option to switch automatically to domestic towns water network
� The system must be fully automated with option to control manually
� The system components must be as standard as possible, in case they need to be placed with new ones
� The system must be designed so the regular maintainance can be done with ease
2.1 Key components design
Rain water reservuar must be installed to the building basement because:
1. Urban buildings (schools, hospitals, hotells) consist of many water consumers. One m3 water is just enough to flush toilet for 166 times. The system must be capable to store numerous m3 of water especially for the fire water purposes and fact that it does not rain every day to refill the reservuars. One m3 of water weighs a ton. So if the building rain water consumption is calculated to be 20 m3 per 10 days it states that the building structure must cope with 20 tons. It is very green to think how to let the gravity do the water pressure work but in fact not all urban existing buildings are designed to hold 20 tons on the 9th strore floor. In long term, maybe it is cheaper to pay for the pump electricity consuption than spending it on the extra construction materials and work costs
2. The water level drop in reservuar causes drop of the water potential energy. I do�nt think that it is nice spend five minutes for the waiting of toilet tank to be filled up. The fire sprinkel system needs to have continious pressure so the waterpumps are unevoidable
3. Many architects like to design buildings by using their favorite green materials like wood. Wooden building structure is not something that manages to hold rain water reservuar weighing several tons
4. The big reservuar can not be split into many smaller reservuars in hope to divide the gravity pressure on many surfaces- need for extra piping, reservuar construction and automation systems make the whole green system by extra cost very unattractive
5. Urban buildings are surrounded with dense network of streets, other buildings, power- gas and waterlines. The facilities literally sit on each other backs. There is no space to build reservuar tower outside the building
6. Towns water pipeline is mostly situated underground so it is very confortable to connect the pipeline through the basement wall to the rain water supply system
The reservuar tanks diameter (if installed horizontally) must be for example 1.5m so it with ventilation piping can fit between the basement celing and floor (ca 2.5m). Human access to the reservuar must be guaranteed for maintenance or need to access water.
There must be option to connect multiple reservuar tanks to the system in case it has economical potentional and the customer wants so. Customer must have option to choose between several tank sizes.
Reservuar material should be regular steel (Steel 25) with corrosion protection level C5. There is no need to �overkill� the design by multiple times more expensive stainless steel just because its polished surface looks great. Also we must keep in our mind that we are dealing here with industrial purposes rain water not with food industry cirups- no need to pay attention on clinical hygien.
Since liquids can not be compressed, all tanks that hold liquids need to have atmosphere access (they need to let air out when water level in tank increases). Water can not access to completely sealed tanks when the air is trapped inside.
There is always opportunity that after hard raining the reservuar will exeed its capacity and the overlow water needs to be guided to a) second reservuar or b) sewer.
Switching to towns water
It is nice to think about endless rain water supply, unfortunatelly real life sets many twists that need to be considered in design process. On poor rainseason or with high rain water consumption the reservuars will finally get empty and in that case the system needs automated switch to traditional towns water supply. Rain water supply system is alternative solution to decrease drinkable water consumption but like most weather conditions, raining is unstable. This switching systems asks for submerged water level sensor in reservuar and electrically controlled valve. After certain fixed water level rise in reservuar the valve automatically switches back to rain water supply. On the system maintenance period is also need for switch to towns water supply.
Like mentioned earlier, pumps have vital part in the water circulation system. Because of the importance of this link, 2 pumps (main pump and backup pump) are needed incase one has some kind of malmfunction or needs to be mainteined- the water must be under pressure all the time. This sets need for automated electrically controlled 2nd valve and waterflow sensor that is installed right after main pump.
The system must have monitoring devices such as individual reservuar water level indicators and manual valve to check the condition (purity) of the rain water in the reservuar.
Rain water filters
Rain water draining from roofs can bring many unwanted solid small particles (like sand and organic elements) to the system, causing malmfunction, wear and tear and piping clogging. Installed roof water draining pipe nets will catch only bigger parts like flying waste, tree leaves and their seeds but not smallest harmful particles. Rain water supply system must have atleast two industrial filters installed before reservuars. The first filter would catch bigger particles and the second one smaller particles. The smaller particles escape from the filters, the longer is the maintenance period and operation life expetation of the systems (pumps, valves and devices attached to the rain water supply chain).
Electrically controlled valves, pumps, sensors, their cabeling and circuit board must be isolated from the possible basement floor water accident. Author suggests to lift electrical application from the floor, this not only eliminates electrical failure but also helps to prevent damaging cabeling by steping on it, increases safety and makes system maintenance more comfortable (application is on the waste level).
�What if� situations
Automated control makes the system confortable to use but there should also be option to control circulation manually (incase of electrical failure)- system must be equipped with manual valves. The reservuars need to be taken individually so their drainage and ventilation should be independant from the others. If one reservuar needs to be maintained then the whole system should not be shut down. If one waterpump stops working then the system must not shut down. Mentioned problem was previously solved by additional backup pump and water flow sensor.