How often should you add salt to a water softener?

Short answer

Check every month, top up every 1 to 2 months. The salt lives in the brine tank, the big bin beside or inside the softener, and the rule of thumb is to keep it at least half full. A large household, or very hard water, goes through salt faster, so check every 2 weeks. A look takes a minute, and a top-up takes 5 to 15 minutes and $5 to $15 in salt.

Why it matters

A softener works by trading the calcium and magnesium in hard water for sodium held on a bed of resin beads. The beads fill up, and every few days the softener flushes them with salty water from the brine tank to recharge them. That's the whole system, and it runs on salt. When the tank runs empty, the resin can't recharge, and hard water goes through to the house as if the softener weren't there.

You'll notice within a week or so: spots on the dishes, soap that won't lather, scale creeping back onto the faucets. What you won't notice is the scale building inside the water heater and the pipes, which is the expensive part. A softener left without salt for a long stretch also lets its resin foul with iron and minerals, and fouled resin doesn't come all the way back when the salt returns. Keeping the tank topped up is the easiest job in the house, and skipping it undoes everything the softener was bought for.

When to do it more often

A large household uses more water, so the softener recharges more often and eats salt faster. Very hard water does the same, because the resin fills faster and needs more frequent recharging. In either case, check every 2 weeks until you learn how fast your tank drops, then settle into a rhythm.

The other thing to check for, more often in a humid basement, is a salt bridge: a hard crust that forms across the top of the tank with a hollow underneath. The tank looks full, but the salt isn't reaching the water below, and the softener is quietly out of service.

What you need

A broom handle, to break up a salt bridge
Water softener salt, in pellets or crystals, as the softener's manual recommends

Steps at a glance

Lift the lid on the brine tank and look at the salt level.
Push the broom handle gently into the salt in a few places. If it breaks through a crust into a hollow, that's a bridge, so break the whole crust up.
If the level is below half, pour in salt until the tank is a little over half full, without packing it to the top.
Wipe any salt off the lid's seal and close the tank.
Note the date, so you know the rate the tank drops.
Once a year, look in the tank for sludge at the bottom, and clean it out if the salt sits in gray mud.

You're done when the tank is at least half full of loose salt and the broom handle sinks into it without hitting a crust.

Signs it's overdue

The salt level is low, or a hard crust has formed with a hollow beneath it.
Water spots on dishes and glasses, back after they'd gone.
Scale on faucets and showerheads.
Soap that won't lather the way it did.

DIY or pro

Topping up salt is as easy as it sounds, and the bag is the only weight involved. Breaking a salt bridge takes no skill either, just the broom handle and some patience. There's no reason to pay anyone for either.

An annual service visit, at $100 to $200, is a different job. A technician checks the resin, cleans the brine tank and the injector, tests the water hardness, and adjusts the softener's settings for your actual usage. It's worth it every year or so on an older softener, or on any softener that's leaving hard water through even with salt in the tank. If salt is in the tank and the water is still hard, the softener needs the service, not more salt.

FAQ

How do I know if my water softener needs salt?

Open the brine tank. If the salt is below half, or you can see water above the salt, add more. Hard water symptoms coming back is the other sign.

What is a salt bridge in a water softener?

A hard crust of salt across the tank with an empty space below it. The tank looks full but the water underneath has no salt to dissolve. Break it up with a broom handle.

Can I use any salt in a water softener?

Use salt sold for softeners, in pellets or crystals as the manual says. Table salt, rock salt and ice-melt salt leave residue that clogs the system.

Why is my water still hard with salt in the tank?

A salt bridge is the usual cause. If the salt is loose and the water is still hard, the softener's settings, injector or resin need a service visit.