Schools K - 12 Introduction
Implementing water conservation in schools offers two-fold benefits; water is saved at the facility, and the students receive practical education and experience on the merits of water conservation. The high person/fixture ratio results in very high frequency of use leading to a very fast payback on many conservation investments. While the savings potential is huge, implementation is sometimes impeded by budgetary restrictions of the schools. When selecting water efficient equipment, it is important to consider durability and tamper resistance wherever students have access to the fixtures, equipment and appliances. High schools are considered one of the most abusive environments for sanitary fixtures. The common water conserving opportunities are as follows.
Water savings can be achieved by replacing older model toilets using 3.5 GPF (13.2 LPF) or greater with new ULFTs (1.6 GPF (6.1 LPF)), HETs (1.28 GPF (4.84 LPF)), or dual flush toilets using 1.6 GPF for solid waste and 1.0 GPF for liquid waste. The frequency of toilet flushes per toilet is often greater in schools than many other CII facilities, although the frequency is highly variable from school to school. It is reasonable to assume an average of 2 to 4 flushes per student per school day. To calculate forecasted savings, the quantity of students per toilet is the most important factor. Faculty and staff often have separate lavatory facilities; requiring separate calculations.
When conducting benefit/cost analyses, it is important to separate the calculations for female toilets versus male toilets for two reasons: (1) the ratio of boy’s room toilets per male student is usually different than the ratio of girl’s room toilets per female student; (2) boys will most often use urinals (when available) rather than toilets. While it is reasonable to use average toilet usage estimates for program planning; performing toilet retrofit projections on individual school facilities requires calculations based on unique site data. A sample calculation might be:
Data: 180 school days per year
200 male students, 250 female students
5 male toilets, 15 urinals
20 female toilets
Male Toilet Flush Quantities:
180 days X 200 males X 0.5 toilet flushes/day = 18,000 toilet flushes/year
18,000 flushes / 5 toilets = 3,600 flushes/year/male toilet
Male Urinal Flush Quantities:
180 days X 200 males X 2.5 urinal flushes/day = 90,000 urinal flushes/year
90,000 flushes / 15 urinals = 6,000 urinal flushes/year/urinal
Female Toilet Flush Quantities:
180 days X 250 females X 3 toilet flushes/day = 135,000 toilet flushes/year
135,000 flushes / 20 toilets = 6,700 flushes/year/female toilet
Conclusion: This example shows replacing female toilets will garner more than twice the water savings compared to male toilets.
The predominant type of toilet in schools is flush-o-meter toilets (tanklesss). Both the bowl and the flush valve of the flush-o-meter toilets must be replaced to assure water savings and adequate flushing performance. The cost to replace a flush-o-meter type toilet usually ranges from $250 to $400, depending on the type of toilet required. Wall-mounted toilets are usually the most expensive to replace; and toilet models suitable for such retrofits are limited.
In addition, some schools provide child size toilets for kindergarteners; these are usually gravity tank type and very expensive (due to limited market). The high cost of replacement usually dictates these toilets not be part of the toilet replacement plan.
As with all toilets in the commercial sector, there are a few extras items to consider:
- To retain water savings, building maintenance staff must be trained to only use the proper parts when servicing the flush valves. Unfortunately, 3.5 GPF ( 13.2 LPF) parts often fit the new 1.6 GPF (6.1 LPF) flush valves.
- Replacement options include the 1.6 GPF (6.1 LPF) toilets, and there are now HET 1.28 GPF (4.84 LPF) models available.
- Sensor flush mechanisms often result in more frequent toilet flushing than manual flush valves. There is no evidence the sensors valves save water.
- If installing dual flush toilets, it is wise to post instructions for the students and provide classroom instruction on their use and benefits.
- Disposable seat covers and paper towels are the most common causes of clogged toilets. Consider alternate methods of hygiene (sanitizers, continuous roll seat cover dispensers, air dryers, etc.), or select new toilets models that exceed 500 grams (1.10 pounds) in MaP Testing.
- Flushing performance is very important for success. Refer the MaP testing before selecting new toilets.
The benefit of replacing urinals is highly dependant on frequency of use and the type of proposed urinal replacement. Frequency of use is determined by calculating the quantity of male students and school days per year, the average urinal flush per student (usually 2 to 4 per school day), and the quantity of urinals.
There are many options now for urinal replacements; from simply replacing the flush valve to reduced flows, to replacing the entire urinal to a zero water use model. All options vary in the costs and benefits. In many cases, minimal water savings can be achieved by simply altering the urinal flush valve to a lower GPF diaphragm, though some older urinals will not properly function at these reduced flows. Unfortunately, this type of valve retrofit can be easily and mistakenly reverted back to the higher flush volume during routine maintenance. Much consideration is needed to determine the best retrofit or replacement for any given school. To assure water savings are maintained over time, the best strategy is to replace the entire urinal and flush valve with a 0.125 GPF or 0.25 GPF (.47 LPF or .94 LPF) model urinal, or a non-water urinal.
As with all urinals in the commercial sector, there are a few extras items to consider:
- Maintenance staff must be trained to only use the proper parts when servicing the flush valves; or all water savings will be negated. Unfortunately, 3.5 GPF (13.2 LPF) parts often fit the new 1.0 GPF (3.78 LPF) flush valves.
- Sensor flush mechanisms often result in more frequent urinal flushing than manual flush valves. There is no evidence the sensors valves save water. There is no sanitary need for the urinal to be flushed after every use.
- Non water urinals are considered compliant by most plumbing code authorities. The Uniform Plumbing Code and the International Plumbing code allow the urinals, but some local cities and counties have not yet approved the devices.
- Urinals are one the favorite targets of vandalism in schools. Extra considerations must be made to assure the selected replacement urinals and the installations are durable to withstand the abuse. Some schools have chosen fiberglass non-water urinals as a means to combat vandalism and floor flooding.
Showering facilities are often found in schools for PE classes and sports teams of the school. The Energy Policy Act of 1995 set maximum showerhead flow rates rate at 2.5 gallons per minute (GPM)(9.5 LPM). Despite this federal mandate, some showers flows can still be found flowing in excess of 5 GPM (18.92). In addition, many showerheads are easily altered (removal of the flow restrictor disc) to higher flow rates. Replacing excessive flow showerheads is one of the most cost effective retrofits inside schools.
New, well-designed 2.5 GPM (9.5 LPM) showerheads offer a satisfying and effective shower experience for dorm residents. There are some models of showerheads that flow less than 2.5 GPM (9.5 LPM) and also have high levels of consumer satisfaction, but these are not recommended for safety concerns. As showerhead flow rates have decreased, the incidents of accidental scalding have increased; caused by the loss of thermal buffering in water volume when supply water temperature changes suddenly. Thermostatic mixing valves prevent this problem, and are now required by most plumbing codes. To date, thermostatic mixing valves are only tested and certified for flows of 2.5 GPM (9.5 LPM) or greater. Installing showerheads with flow rates below 2.5 GPM (9.5 LPM) is not recommended until thermostatic mixing valve requirements are amended to lower flows.=
Water savings projections can be easily estimated by measuring the flow rates of the pre-existing showerheads, determining quantity of showers/day, and calculating the water use differential. One variable is estimating the average duration of the showers. It is usually assumed that using private shower stalls result in longer showering times, compared to ‘gang shower stalls’ (large shower stalls with multiple showerheads) commonly found in school gymnasiums. Anecdotal evidence suggests showering duration at schools is far shorter than the measured average of 10.6 minutes/shower occurring in homes.
It is very important to choose replacement showerheads that are tamper proof. High schools are considered one of the most abusive environments for plumbing fixtures. Water savings will only be achieved if the new showerhead is retained and not altered to excessive flows. Most high quality showerheads cost $5 to $12 in bulk quantities. We do not recommend using price as sole criteria when selecting showerheads for dormitories.
Flow rates for wash basin faucets in office lavatories can reasonably be reduced to 1.0 GPM (3.78 LPM) or lower. Projected savings are usually based on usage frequencies similar to toilet and urinal use. Flow durations are often estimated to average 5 to 30 seconds per use. Retrofitting aerators on the faucets is the most common strategy, and relatively inexpensive. The water savings are small when compared to replacing toilets, but the cost of retrofit is minor; usually less than $1.00 per faucet.
Most school wash basins are fitted with mechanical metering valves (automatically shut-off after a preset time span) or negative shut-off valves (user must continue to exert pressure on valve handle to maintain water flow). These types of valves are required to deter vandalism of students purposefully flooding the lavatories. The valves are often adjustable for the duration of the flow. The flow should not exceed 5 seconds per activation.
It is never recommended these mechanical metering valves be replaced with infrared sensor type valves. There is no scientific evidence that sensor activated faucets save water. To the contrary, recent studies have provided valid evidence that sensor faucets use much greater water than manually activated valves. Sensor activated valves provide user convenience, but are now known to be wasters of water.
Most schools have extensive landscaping, especially recreation and sporting venues (playgrounds, football, baseball, soccer fields). Where local climate demands regular irrigation, there are often vast opportunities for water savings from improving irrigation systems and practices. Water efficiency measures often achieve water savings of 30% to 50% of all irrigation water. Artificial tuf is an option to reduce water use, but should be used cautiously. The Center for Disease Control has issued a preliminary warning of health concerns: http://www2a.cdc.gov/HAN/ArchiveSys/ViewMsgV.asp?AlertNum=00275
Many schools serve lunch to students; and this presents excellent opportunities to conserve water in the areas of food preperation and dish washing. Food is often heated in steamers using a central boiler; connectionless steamers are alternative equipment that saves thousands of gallons of water per year. Pre-rinse spray valves, using 4 GPM (15.1 LPM) are used to rinse dishes before placed in the dishwasher; new efficient spray valves use only 1.6 GPM (6.1 LPM) and save hundreds of gallons per day (depending on volume and type of meals served).
Some schools employ the use of a cooling tower in the HVAC system to cool the building. Cooling towers use the cooling effect of evaporating water to remove heat from water circulating through the HVAC chillers. There are numerous ways for the system to waste water when the system is not properly maintained. Depending on the climate zone and the cooling system, the water wasted can be greater than all the sanitary fixtures combined. Appropriate retrofits usually require a conductivity controller be installed and properly maintained to achieve water efficiency. Conductivity controller retrofits, usually cost less than $1,500 per cooling tower, can save more than $800 per year for a typical office building.
There are ample technologies available to greatly improve the water efficiencies of most cooling tower systems. Technology provides the tools for water savings, but does not guarantee water efficiency. Controller installations and retrofits must be part of an overall customer maintenance and education program to be effective.
Where the local wastewater treatment agency provides reclaimed water (wastewater treated to drinking water standards, though deemed non-potable), schools provide an opportunity to supplant potable water use with reclaimed water use. Landscape irrigation is the most obvious opportunity to use this water. Reclaimed water can also be used to supply water to toilets and urinals. Depending on the water quality requirements, many cooling towers can also use reclaimed water rather than potable water.
In all applications, the reclaimed water must be strictly separated from potable water sources and end-uses. This requires a clear separation of pipes supplying water to the end use (irrigation system, toilets, urinals, cooling tower, etc) from pipes supplying potable water to faucets, drinking fountains, etc. Irrigation systems are usually on separate meters and water supplies; thus, this is the most common application for reclaimed water use.
In existing buildings, the water supply pipes for toilets and urinals are often interconnected with faucets and drinking water fountains; requiring extensive plumbing system retrofits if reclaimed water is to be used. Retrofitting a pre-existing plumbing system inside a school is usually too costly to justify the use of reclaimed water to flush sanitary fixtures.
When constructing a school, the cost to separate the water supply pipes for sanitary fixtures is marginal. Many water agencies are now requiring new public buildings be designed with dual plumbing to separate the plumbing so reclaimed water can be used to flush sanitary fixtures, even if reclaimed water is not immediately available. Plumbing contractors this has ads less than 15% to the total cost of the plumbing system.
Storm Water Collection and Use
Collecting the rainwater on the building site (roof, parking lot, hardscape, landscape, etc.) is one of the fastest growing strategies in the water conservation industry and the “green” building efforts. There are three distinct advantages to storm water collection and use:
- The collected water can be stored then used to irrigate the landscape during dryer months.
- The water collected is prevented from entering the storm water system, which is often overtaxed in urban areas causing flash floods.
- The pollutants from the building site (fertilizers, herbicides, pesticides, animal waste, automobile fluids, etc) are prevented from being carried by storm water to streams, rivers, and other aquatic ecosystems. These pollutants are classified as ‘non-source point pollution’, and recent studies have shown the profound negative effect on local water quality.