How PurAll Works
Schematic of installation of purall model for piped water supply schemes.
It is recommended that PurAll device be connected to the main raw water supply line as per Fig 1above. Only in rare case, if installation as per Fig 1 above is not possible, then PurAll be installed as per Fig 2 above. The valves used should be of the type that will not restrict the flow very much, such as ball valves or gate valves. During operation it will be necessary to take samples downstream of PurAll to check the chlorine residual. The sample must be drawn after the chlorinated flow has merged with the bypassed flow. A sample tap might be installed for this purpose.
In operation, the water flows by gravity through the bypass line (Fig 1) or in a pressurized bypass line (Fig2) through PurAll. In this arrangement adequately chlorinated water is mixed in raw water to have desired free chlorine The dose should remain relatively constant regardless of the rate of flow.
The chlorine dose so adjusted should be sufficient to satisfy the chlorine demand and provide a residual level in the distribution system. If PurAll adds more chlorine to the water than is needed for these purposes, the chlorine dose can be controlled by the amount of water bypassing PurAll. To increase or decrease the dose the bypass valve may be adjusted to divert more or less water through PurAll. During operation the bypass valve will normally be partially or completely closed for flow control and the isolation valve will be partially or wide open. The valves once adjusted are seldom required to be changed for a site, unless there is a marked change in raw water parameters- viz flow rate.
