So, you are going to include a water feature in your project….
When you get a project that has a fountain in it, soon or later you will get asked by the engineers what you will need in the way of utilities. The list is very simple, but the implications of what you choose can be costly to the project and/or the maintenance cost of the fountain. The requirements will differ depending on whether the fountain is inside or outdoors and whether you have an equipment space within a building or if you are going to have an equipment space or vault outside.
Here is how it works out:
We most often ask for a 1-1/2” water supply with backflow protection. This means that the water source for the fountain is protected separately from the building or project potable water supply. An 1-1/2” pipe can fill a fountain at a flow rate of about 125 gallons per minute or 7,500 gallons per hour. If your fountain is small, you can probably live with a 1” water supply and if it is large, you may want to increase the size based on how long you are willing to live with filling the pool. Remember that these water supply sizes can sometimes affect tap fees adversely, so you have to weigh the value of fill time during maintenance and capital costs.
Once water enters the pool it is non potable and once you put chemicals in it, the water should be drained to sanitary. Any drain in the pool should be connected to sanitary, typically 3” will suffice. In the equipment space, you will also need a connection to sanitary for any nuisance water that spills during maintenance and for the filters to drain the backwash water to. Sanitary systems are gravity drains and engineers do not like pumping directly into the pipes, so filter systems that backwash have to discharge into tanks that trickle drain to sanitary. This requires you to design a tank in the equipment space with a drain in it to handle the backwash volume. For coordination purposes, if your fountain and equipment are outside, you will ask the Civil engineer for a 3” sanitary connection at the pool and at the equipment room or vault. If your fountain and equipment is inside, this would be asked of the MEP engineer.
Storm sewers are typically required for the overflow drains for fountains as municipalities do not like to charge their sanitary systems during a storm event. The eternal question however, has always been if it rains in your fountain does the rain water mix with the chlorinated water? Of course it does, and during a rain event you would be sending diluted chlorinated water to storm. Some municipalities like Los Angeles require you to connect your overflows to sanitary, some still want it connected to storm. In either case a 3” overflow is normal but you should ask your civil engineer what is allowed and design appropriately.
The power supply for your fountain installation is somewhat dependent on how big your fountain is and how many lights you have in it. For smaller installations, 120/240 Volt single phase power is enough to run a small pump or two and some lights. For larger projects, a typical voltage is 120/208 volt, 3 phase power. This will handle most pump sizes for medium to large fountains. On some projects the electrical engineer will require that all pumps run on 480 volts, 3 phase power and on these projects your designer will need to ask for a low voltage supply as well. While all of the pumps and most of the equipment can run at high voltage, the controls for the fountain almost always run at 120 volts or even lower 24 volts. It is always preferable to have the electrical engineer provide a secondary power supply or a stepdown transformer for control power.
Fountain pumps and controls generate heat and will require that the room be ventilated. If the equipment is inside, it is best if the room is air conditioned but in some cases they are not. We typically ask for 25 cfm per horsepower in the room. If the equipment is outside in a vault, we often add dehumidifiers. In extreme climates such as the middle east, we have used split unit air conditioners. A connection for the ventilation system to run when the pumps run, and a thermostat and humidistat would be good choices for a control package.
The most common “what if” is the project that does not have sanitary sewer close by or at all – typically a park or plaza. Your choices are somewhat limited to either designing an ejection system into a manhole that will pump your fountain water however far away it has to to reach the sanitary line, or design a holding tank to pump your water into for it to sit and dissipate the chlorine before ejecting it to storm sewer. Most chlorine will dissipate from water within 12 hours, so the hold time is not that great, but the tank and controls are expensive as is the manhole ejection system. You can design a fountain that does not use chlorine, but the likelihood is great that someone sometime will dump chlorine into it to get rid of algae.
Take all of these items into consideration, and you are off to a great start on a successful water feature design.