Direct answer: To regenerate a North Star NSC22, NSC31 or NSC42 now, press and hold RECHARGE for 3 seconds until “RECHARGE,” “Serv” and “Fill” flash; the manuals say the regeneration takes about 2 hours. To schedule one for the next recharge time (2:00 AM by default), press and release RECHARGE so “RECHARGE TONIGHT” flashes, and press it again to cancel. In normal use the controller decides on its own, from metered water use, and picks a salt dose at each recharge. Optional settings change that behavior: Salt Efficiency, the Clean feature, maximum days between regenerations, and the 97% feature, which lets a regeneration start at any hour.
Publisher boundary: Water System Guide is an independent research publisher, not North Star support. This guide covers manual 7393624 (NSC22 and NSC31) and manual 7393632 (NSC42), both Rev. H dated January 7, 2026, reviewed October 15, 2026. It does not cover NST two-tank models, the NSCWC and NSCWHC systems, or Wi-Fi app controls.
How the controller decides to regenerate
North Star softeners have a demand initiated regeneration (D.I.R.) feature, and “the salt dose is selected by the electronic controls at regeneration time based on the amount needed” (NSC31 manual, PDF page 3). The controller counts gallons through a turbine meter and compares use with the programmed hardness. The rated capacities show how the dose changes what a regeneration restores:
| Salt dose point | NSC22 | NSC31 | NSC42 |
|---|---|---|---|
| Lowest | 8,700 grains at 1.9 lbs. | 12,300 grains at 2.4 lbs. | 12,400 grains at 2.5 lbs. |
| Middle | 18,500 grains at 6.2 lbs. | 26,200 grains at 7.7 lbs. | 33,300 grains at 9.5 lbs. |
| Highest | 22,100 grains at 10.4 lbs. | 31,300 grains at 12.9 lbs. | 42,100 grains at 16.3 lbs. |
| Water per regeneration at maximum dose | 30.4 gallons | 31.1 gallons | 45.9 gallons |
Sources: NSC22/NSC31 specifications; NSC42 specifications.
The recharge time, 2:00 AM by default and adjustable in one-hour steps, is when a needed regeneration starts. The manual’s reason: “Hard water bypasses the softener if the household draws water during the recharge cycle” (NSC31 manual, PDF page 13).
Recharge Now
The manuals name two situations for a manual regeneration: heavier water use than normal, such as guests, or running out of salt. In the second case, “add salt to the softener before regenerating” (NSC31 manual, PDF page 14).
- Check that salt is touching the water and there is no salt bridge.
- Press and hold RECHARGE for 3 seconds until “RECHARGE,” “Serv” and “Fill” flash.
- The softener enters the fill cycle immediately. “This regeneration will take about 2 hours to complete. Then, you will have soft water again.”
If the Clean feature is ON, the normal cycle is preceded by an extra backwash and rinse; “CLEAN” and “Bkwsh” or “Rinse” flash with the minutes remaining.
Avoid hot water during the regeneration. The troubleshooting table lists hot water use during regeneration as a cause of intermittent hard water, because the water heater refills with hard water.
Recharge Tonight
Press and release RECHARGE without holding. “RECHARGE TONIGHT” flashes, and regeneration starts at the next preset recharge time. Press and release again to cancel; the flashing stops. Use this after refilling salt in the evening.
Reading the display during a regeneration
While recharging, the display shows a valve position indicator: Serv, Fill, Brine, Bkwsh or Rinse. “RECHARGE” flashes, and beginning with Brine the minutes remaining replace the time of day. When the valve moves between cycles, both indicators flash (NSC31 manual, PDF page 17). If power is lost mid-regeneration, the manual says the softener “will now finish the cycle” when power returns.
The manual’s regeneration check walks through those positions (NSC31 manual, PDF page 22):
- Fill: fill water visibly enters the salt tank through the brinewell.
- Brining: a slow flow to the drain while the brinewell liquid level drops noticeably.
- Backwash: a fast flow from the drain hose.
- Fast rinse: another fast flow that flushes remaining brine.
- Service: back to soft water.
If brine is not drawn, the manual’s list is: dirty nozzle or venturi, nozzle and venturi not seated on the gasket, a restricted drain, an ineffective nozzle and venturi seal, or another inner valve problem such as the rotor seal, rotor and disc or wave washer. Valve faults that stop the motor raise an error code; see our North Star error code guide.
Optional settings that change regeneration
Hold SELECT for 3 seconds until “000” shows, then press SELECT to step through the optional screens (NSC31 manual, PDF page 15). All of these appear in both manuals.
Salt Efficiency. When ON, the softener runs at 4,000 grains of hardness per pound of salt or higher and “may recharge more often using smaller salt dosage and less water.” It ships OFF. Installations in California must turn it ON.
Clean feature. For water with iron or high sediment, a backwash and fast rinse run before the normal regeneration. The default is OFF, and the manual says to keep it OFF when there is no iron or sediment, to conserve water. Clean minutes default to a model-dependent value and can be set from 1 to 15.
Maximum days between regenerations. The controller normally sets frequency itself, and “under most conditions this feature will be left in its default mode.” You can force a regeneration every set number of days, up to 15, for example to keep a resin bed clean on water with iron.
97% feature. This “can save salt and water by regenerating when 97% of the softener’s capacity has been used up.” With it ON, “the regeneration can occur at any time,” not just at the recharge time. The default is OFF (NSC31 manual, PDF page 16). The trade-off is the hard-water bypass the manual warns about: a daytime regeneration sends untreated water to the house while it runs.
Backwash and fast rinse times. Default times depend on the model and can be set between 1 and 30 minutes each. The manual warns that times set too low “may result in salty tasting water after regeneration.”
Write down each value before changing it. Our North Star settings guide covers time, hardness and the NSC42’s salt-type screen.
Salt and brine
Regeneration depends on brine. The manuals recommend “nugget, pellet or coarse solar salts with less than 1% impurities” and list rock salt, block, granulated, table, ice-melting and ice-cream salts as not recommended (NSC31 manual, PDF page 18). Check the salt every two or three weeks until you know the pattern, and add salt whenever the tank is less than 1/4 full. In humid areas, keep the level lower and refill more often to avoid bridging.
The NSC42 has a salt-type screen for NaCl or KCl that “adjusts the regeneration cycle times to compensate for the different rate at which KCl dissolves” (NSC42 manual, PDF page 13). The reviewed NSC22/NSC31 manual has no salt-type step.
After adding salt, press SET SALT LEVEL until the bars match the number on the brinewell scale. The manuals note that “the salt monitor system estimates salt levels, and accuracy will vary with different salts.” Our salt guide compares salt types.
Regeneration during sanitizing
After installation or service, the manuals suggest sanitizing: pour about 3 oz. (6 tablespoons) of household bleach into the brinewell, make sure the bypass is in service, and start a Recharge Now so the bleach is drawn through the softener. When it finishes, run a cold faucet downstream until 50 gallons pass, which “should take at least 20 minutes” (NSC31 manual, PDF page 11).
After the salt runs out
Running the tank dry is the most common reason owners regenerate by hand. The troubleshooting table’s first row is “No soft water: no salt in the storage tank,” and its correction is “Refill with salt and then use RECHARGE NOW feature” (NSC31 manual, PDF page 20). In practice:
- Add recommended salt and level it.
- Set the salt level so the low salt light stops flashing.
- Start Recharge Now and avoid hot water for about 2 hours.
- Retest soft water after the regeneration.
If one regeneration does not restore soft water, check for the causes the table lists next, a salt bridge, a bypass valve left in bypass or a plugged nozzle and venturi, before starting another cycle or calling the contractor.
Frequently asked questions
How do I manually regenerate a North Star water softener?
Press and hold RECHARGE for 3 seconds until “RECHARGE,” “Serv” and “Fill” flash. The manuals say the regeneration takes about 2 hours.
What is the 97% feature on a North Star softener?
An optional setting that starts a regeneration when 97% of capacity has been used, at any time of day. The manual says it can save salt and water. It is OFF by default.
How long does a North Star regeneration take?
About 2 hours, according to the NSC22/NSC31 and NSC42 manuals. With the Clean feature ON, an extra backwash and rinse run first.
Will a North Star softener finish regenerating after a power outage?
Yes. The manuals say that if the softener was regenerating when power was lost, it will finish the cycle when power returns. Reset the clock only if it is flashing.