added through a 2- or 3-inch half-coupling (with brass plug), provided in the upper head of the shell or through the manhole cover plate.

3. Replace the ion-exchange bed with new resin whenever the inspection indicates the need, or when the exchange capacity has decreased and cannot be restored by cleaning and special procedures recommended by the manufacturer.

4. Quarterly, probe through the resin bed to determine the surface of the supporting gravel. The surface should be relatively even with a maximum difference of 4 inches between high and low spots. Any indication of shifting gravel bed, caking, or other difficulties, calls for repair efforts. Uneven gravel may be raked smooth, through the open manhole, during backwashing operations.

When gravel needs to be removed, it may be cheaper to install new gravel than to remove, wash, and regrade old gravel. New gravel should be lime-free (do not use ordinary river gravel). When old gravel is reused, screen out all resin particles. Spraying with water is the best method of removing the resin from the gravel on the screen.

Replace or add new gravel in four layers. Fill the shell with water to the depth desired, then add the coarsest grade first; level the gravel layer to fill low spots; next, raise the water level to the next depth required and add the next smaller grade. Repeat the process; then, add the resin to the desired depth and classify by backwashing the bed.

Annually, or as necessary, the condition of underdrains may be learned from the pressure drop across the underdrain system with a full backwash flow being discharged from the manhole. A greater pressure drop than existed at the time of installation shows plugging underdrains; a lesser pressure drop reveals displaced or corroded nozzles. Underdrains should be inspected, removed, cleaned, painted (where necessary), and replaced every 3 years

Manifold-type underdrains should be inspected when gravel is removed. Remove several laterals at random and check for clogging. Where clogging is evident, remove all laterals and clean mechanically, or treat with inhibited muriatic acid.

Plate-type underdrains should be removed, inspected, painted, and replaced every 3 years; make certain that the clearance space between the plate and lower head is the same at all points.

REGENERATION EQUIPMENT

For regeneration equipment, the maintenance procedures are as follows:

1. The salt storage tank should be cleaned at varying periods, depending on the amount of insolubles in the salt, tank size, and the salt usage. Rock salt contains more insolubles than evaporated salt. (The greater the salt usage, the more frequent the cleaning required.)

2. The brine-measuring tank should be cleaned every 6 months, and both exterior and interior surfaces painted.

3. At annual intervals, the brine ejector should be cleaned, disassembled, and checked for erosion or corrosion; any clogging of piping should be removed before the ejector is reassembled and replaced.

The maintenance operation frequency and schedule of inspections for ion-exchange softening units are shown in appendix III, table D.

Q8. The exterior shell of a water softener unit should be cleaned a minimum of what frequency?

Q9. Does a water softener need to be removed from service when multiport valves are lubricated?

Q10. When flushing ion-exchange beds with chlorinated water, the water used should be of what pH?.

Q11.Of the salts used in softening water, which contains less insolubles, rocksalt, or evaporated salt?

MAINTENANCE OF CLARIFICATION EQUIPMENT

LEARNING OBJECTIVE: Identify and understand basic maintenance procedures for clarification equipment.

Maintenance procedures for clarification equipment are discussed below. The equipment includes mixers, flocculator basins, and sedimentation basins. 8-7