The instructions will specify an amount of salt to use (pounds/kilos) to recharge the particular capacity of your unit. You run water through until all the salt has dissolved and percolated through the resin bed, completing the ion exchange which charges the resin to then soften the water through the reverse ion exchange.
Every 2-3 recharges usually necessitate that you also "backflush" to clear out any "tunneling" of the water flow through the resin bed. Backflushing involves flowing water though the softener in reverse flow for a few minutes. Some softeners have a plumbing valve that permits backflushing without physically reversing your inlet/outlet hoses. The simplest manual units do not have this valve, and you have to backflush by switching inlet & outlet hoses and running the water for a time specified in your instructions guide.
Here are the manual directions for the AC39 Manual Unit
Manually recharge your Hydro-Soft water softener; the following procedure should be followed:
1. Shut off feed water pressure to the system.
2. Remove black fill plug on the top of the black tank adapter.
3. Pour in, pre measured by weight, 10-15 lbs of coarse rock salt through the fill hole and replace the fill plug.
4. Remove the outlet hose line and replace with drain line that can be run directly to a drain.
5. Allow a small trickle, about the size of a pencil, approximately 1/4 gallon a minute, to flow through the unit. Allow the water to run for 30 minutes.
6. After 30 minutes the system will be recharged and may be set up for normal operation.
7. IMPORTANT: Every second recharging, before the above procedures, switch the inlet line to the outlet side of the blue tank adapter and turn the water on, allowing water to flow in the opposite of normal direction, at approximately 2 gallons a minute. This will back flush the resin bed and insure that non- channeling will occur. Run this back-flush cycle for 10 minutes.
