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We then moved on to the restricted flow of FCD problems faced by communities with full Aguaclara water treatment plants. As is discussed in the flow control precipitation experiment Calcium Carbonate Settling Observations laboratory, the higher the concentration of calcium hypochlorite(Ca(ClO)2), the larger the concentration of precipitate that initially settles out. If the solution of Ca(ClO)2 is created and left to settle, it was observed that the amount of precipitate stops forming after three days, as long as the solution is not flowing or being mixed with the atmosphere. As was observed in the Final Restriction of Restricted Flow of Hypochlorinators experiment, if the Ca(ClO)2 solution comes into contact with the atmosphere even after initial settling, mixing, or as the result of being forced through a small orifice (such as the one located in the float valve), the precipitate will continue to be formed. It is believed that this is the result of the solution coming into contact with CO2 in the atmosphere which results in the formation of CaCO3 (Equation 1).

Equation 1. 2Ca(ClO)2 + 2CO2 → 2CaCO3 + 2Cl2 + O2

As was observed in the Carbonate Settling Observations laboratory experiment, more precipitate can form after a concentrated solution of Ca(ClO)2 is diluted with non-distilled water as the result of the calcium's interaction with CO2 (Equation 1). Precipitate could also form as a result of its interaction with other chemical species located in the dilution water.

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As was examined in the Final Restriction of Restricted Flow of Hypochlorinators experiment, if there is a solid material present like plastic or metal when the Ca(ClO)2 solution comes into contact with the atmosphere, the precipitate will form on the surface of the plastic or metal (Figure 3).

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If precipitation forms in the stock tank or at the surface of the constant head bottle over time after the initial settlement, it would flow out of the tanks with the rest of solution or settle out at the bottom of the containers, as was observed in the Final Restriction of Restricted Flow of Hypochlorinators experiment. If it continued through the system with the flow of solution we are confident that this small amount of precipitate would not build up, or impede flow at any point in the system. This leaves us with the float valve orifice. Every instance where we were able to restrict flow from the orifice in the float valve there was a buildup of precipitate all over the surface of the float and the arm holding the float to the rest of the valve. It appears that precipitate is slowly forming in the orifice where the solution first comes into contact with the atmosphere after leaving the tube that flows from the stock tank, eventually restricting flow (Figure 4).

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