Fluoride Action Network

Recommendations for fluoridated school public water supply system

Morbidity and Mortality Weekly Report | September 29, 1995

From: Engineering and Administrative Recommendations for Water Fluoridation, 1995, MMWR, September 29, 1995 / 44(RR-13);1-40



  1. Administration

School water fluoridation is recommended only when the school has its own source of water and is not connected to a community water system. Each state is responsible for determining whether school water fluoridation is desirable and for effecting a written agreement between the state and appropriate school officials. A school water fluoridation program must not be started unless resources are available at the state level to undertake operational and maintenance responsibilities. For example, one full-time school technician should be assigned to every 25-30 schools. The following recommendations should be implemented for a school water fluoridation program:

  1. The state must take the primary responsibility for operating and maintaining school fluoridation equipment. School personnel should be responsible only for monitoring fluoride levels and minimal operation and maintenance of equipment.
  2. For each school being considered for water fluoridation, appropriate state personnel should evaluate and prioritize the following criteria:
    1. Number of students who will benefit;
    2. Natural fluoride level in the school’s drinking water;
    3. Recommended fluoride level of the community water systems in the geographic area where the students live;
    4. Whether the water system for the entire school system (the elementary, middle, and/or the high school) will be fluoridated;
    5. Technical feasibility of fluoridating the school’s water system; and
    6. Evaluation of the fluoride content of water drunk at home by students attending a school being considered for fluoridation. That evaluation must occur before school is selected. In general, if greater than 25% of the children attending the school already receive optimally fluoridated water at home, the school’s water should not be fluoridated (31). None of the existing research on school water fluoridation covers prekindergarten children (63-68).
  3. At a minimum, state personnel should visit annually each school system and provide a thorough inspection and overhaul of the equipment (usually during summer recess or when school is not in session).
  4. The state must provide school administrative officials with operating procedures to follow should an overfeed occur. These operating procedures should address the following:
    1. Shutting down the equipment;
    2. Preventing the consumption of high fluoride concentrations (greater than 10 mg/L) in the drinking water;
    3. Notifying appropriate state personnel; and
    4. Other emergency procedures.

Monitoring and Surveillance

  1. For each school that has a fluoridated water system, a sample of the drinking water must be taken and analyzed for fluoride content before the beginning of each school day. Samples may be taken by appropriate school personnel. This sampling will not prevent fluoride overfeeds but will prevent consumption of high levels of fluoride.
  2. School personnel must divide at least one sample per week, with one portion analyzed for fluoride at the school and the other portion analyzed at the state laboratory. The weekly state test results should be compared with test results obtained at the school to ensure that school personnel are using the proper analytic techniques and that their daily samples are being tested accurately for fluoride.
  3. Optimal fluoride levels in a school water system should be established by the state (Table_5). (State regulations supersede recommendations provided in this report.)

Technical Requirements

  1. General
    1. School water fluoridation systems should be installed only where the water is supplied by a well pump with a uniform flow because varying flow rates can cause problems in consistently maintaining optimal fluoride levels (31).
    2. All school water fluoridation systems should be built with a bypass arrangement so that the fluoridation equipment can be isolated during service and inspection periods without shutting off the school water supply. Most states use a pipe loop, with gate valves isolating such devices as the injection point, meters, strainers, check valves, make-up water, and take-off fittings.
    3. Fluoridation equipment should be placed in an area that is secure from tampering and vandalism.
    4. A routine maintenance schedule should be established. Items to be checked include pump diaphragm, check valve, Y-strainers or sediment filters, injection points (for clogging), flow switch contacts and paddles, saturator tank (for cleaning), pressure switch, solenoid valve, float switch, and foot valve.
    5. All hose connections within reach of the fluoride feed equipment should be provided with a hose bibb vacuum breaker.
    6. Cross-connection control, in conformance with state regulations, must be provided.
    7. State personnel should keep records on the amount of fluoride used at each school.
  2. Sodium Fluoride Saturator Systems
    1. Manually filled saturators should be used in all school fluoridation systems. Upflow saturators generally are recommended because less maintenance is required. Make-up water (i.e., replacement water for the saturator) should be added manually for the following reasons:
      1. Greater protection from an overfeed will be provided because only a finite amount of solution is available and no continuously active (i.e., “hot”) electrical outlet will be necessary; and
      2. Potential problems with sticking solenoid valves are eliminated.
    2. The metering pump must be installed so that it cannot operate unless water is being produced (interlocked). For example, the metering pump must be wired electrically in series with the flow switch and the main well pump.
    3. The metering pump must be plugged only into the circuit containing the overfeed protection; it must be physically impossible to plug the fluoride metering pump into any continuously active (“hot”) electrical outlet. The pump should be plugged only into the circuit containing the interlock protection. One method of ensuring interlock protection is to provide on the metering pump a special, clearly labeled plug that is compatible only with a special outlet on the appropriate electrical circuit. Another method of providing interlock protection is to wire the metering pump directly into the electrical circuit that is tied electrically to the well pump or service pump, so that such hard wiring can be changed only by deliberate action. These methods are especially important with an upflow saturator installation because a solenoid valve requires the continuously active (“hot”) electrical connection.
    4. A flow switch, which is normally in the open position, must be installed in series with the metering pump and the well pump so that the switch must close to activate the metering pump. Flow switches should be properly sized and installed to operate in the flow range encountered at the school. It should be installed upstream from the fluoride injection point.
    5. Metering pumps should be sized to feed fluoride near the midpoint of their range for greatest accuracy. Pumps should always operate between 30%-70% of capacity. Metering pumps that do not meet design specifications should not be installed in schools. Oversized metering pumps should not be used because serious overfeeds can occur if settings on the pump are too high. Conversely, undersized metering pumps can cause erratic fluoride levels.
    6. The fluoride metering pump should be located on a shelf not more than 4 feet (1.2 m) higher than the lowest normal level of liquid in the saturator. Many manufacturers recommend that metering pump be located lower than the liquid level being pumped (i.e., flooded suction). However, a flooded suction line is not recommended in water fluoridation.
    7. The priming switch on the metering pump should be spring-loaded to prevent the pump from being started erroneously with the switch in the priming position.
    8. Two diaphragm-type, antisiphon devices must be installed in the fluoride feed line when a metering pump is used. The antisiphon device should have a diaphragm that is spring-loaded in the closed position. These devices should be located at the fluoride injection point and at the metering pump head on the discharge side. The antisiphon device on the head of the metering pump should be selected so that it will provide the necessary back pressure required by the manufacturer of the metering pump.
    9. All antisiphon devices must be dismantled and visually inspected at least once a year. Repair or replacement schedules should follow the manufacturer’s recommendations. All antisiphon devices should be vacuum tested semiannually. Operation of a fluoridation system without a functional antisiphon device can lead to a serious overfeed.
    10. Sediment filters (20 mesh) should be installed in the water make-up line going to the sodium fluoride saturators, between the softener and the water meter.
    11. A flow restrictor with a maximum flow of 2 gallons (7.6 L) per minute should be installed on all upflow saturators.
    12. In an upflow saturator, either an atmospheric vacuum breaker must be installed or a backflow preventor must be provided in accordance with state or local requirements for cross-connection control. The vacuum breaker must be installed according to the manufacturer’s recommendations.
    13. A master meter on the school water service line and a make-up water meter on the saturator water line are required so that calculations can be made to confirm that the proper amounts of fluoride solution are being fed. These meters should be read daily and the results recorded.
    14. A check valve should be installed in the main water line near the wellhead (in addition to any check valve included in the submersible pump installation). The check valve should be tested at least annually for leakage.
    15. The water used for sodium fluoride saturators should be softened whenever the hardness exceeds 50 ppm (or even less if clearing stoppages or removing scale becomes labor intensive). Only the water used for solution preparation (i.e., the make-up water) needs to be softened.
    16. Unsaturated (i.e., batch-mixed) sodium fluoride solution should not be used in water fluoridation.
    17. Only granular sodium fluoride should be used in saturators because both powdered and very fine sodium fluoride can cause plugging in the saturator.
    18. The minimum depth of sodium fluoride in a saturator should be 12 inches (30.5 cm). This depth should be externally marked on the saturator tank. The saturator should never be filled so high that the undissolved chemical is drawn into the pump suction line.
    19. All sodium fluoride chemicals must conform to the AWWA standard (B-701) to ensure that the drinking water will be safe and potable (43).
  3. Testing Equipment
    1. The colorimetric method (SPADNS) of fluoride analysis is recommended for daily testing in school water fluoridation. If interferences are consistent (e.g., from iron, chloride, phosphate, sulfate, or color), the final fluoride test result can be adjusted for these interferences. State laboratory personnel and the state school technician should reconcile the interference and make the appropriate adjustment.
    2. Distillation is not needed when the colorimetric method (SPADNS) of fluoride analysis is used for testing daily fluoride levels.

Safety Procedures

Fluoride remains a safe compound when maintained at the optimal level in the water supplied to a school water system; however, the school technician could be exposed to excessive levels if proper procedures are not followed or if equipment malfunctions. Thus, the use of PPE is required when fluoride compounds are handled or when maintenance is performed on fluoridation equipment. The state should develop a written program for schools regarding the use of PPE.

  1. Operator Safety
    1. The state school technician should wear the following PPE:
      1. A NIOSH/MSHA-approved, N-series particulate respirator (i.e., chemical mask) with soft rubber face-to-mask seal and replaceable cartridges (49-51);
      2. Gauntlet neoprene gloves with cuffs, which should be a minimum of 12 inches (30.5 cm) long;
      3. Splash-proof safety goggles; and
      4. Heavy-duty, acid-proof neoprene apron.
    2. An eye wash solution should be readily available and easily accessible.
    3. Exposure to fluoride chemicalsIf the operator gets dry chemicals on the skin, he or she should thoroughly wash the contaminated skin area immediately and should change work clothing daily no later than the close of the work day (51).
  2. Recommended Emergency Procedures for Fluoride Overfeeds
    1. Fluoride overfeedsWhen a school system fluoridates its drinking water, a potential exists for a fluoride overfeed. Most overfeeds do not pose an immediate health risk; however, some can be high enough to cause immediate health problems. All overfeeds should be corrected immediately because some can cause long-term health effects (52-55).
      1. Specific actions should be taken when equipment malfunctions or an adverse event occurs that causes a fluoride chemical overfeed in a school public water supply system (Table_6).
      2. When a fluoride test result is at or near the top end of the analyzer scale, the water sample must be diluted and retested to ensure that high fluoride levels are accurately measured.
    2. Ingested fluoride overdosePersons who ingest dry fluoride chemicals should receive emergency treatment (Table_3) (10,56-62).


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