Maintain
How to Sanitize a Water Softener
To sanitize a water softener, pour a measured dose of plain household bleach into the brine well, run a regeneration so the brine carries it through the resin, then rinse and flush the house lines until the chlorine smell is gone.
Quick answer
- Dose: roughly 1 to 2 fl oz unscented bleach per cubic foot of resin.
- Pour it into the brine well, never into the resin tank.
- Run a regeneration with about an hour of contact time.
- Rinse again and flush a cold tap until the chlorine smell clears.
- Sanitize when the water tastes or smells off, or every 6 to 12 months.
When to sanitize
Sanitizing kills bacteria and organic growth inside the softener. It is different from a resin cleaner, which removes iron and other fouling (see resin cleaner), and from cleaning the brine tank, which removes sludge.
According to Pentair's 5600SXT manual, a softener picks up organic matter or bacteria from the incoming water over time; the result is water that tastes or smells off, and the manual's remedy is disinfection. Sanitize when:
- The softened water, or the brine tank, smells musty or of rotten eggs. Our softener smell guide helps you rule out other causes first.
- You have just cleaned the brine tank after mushing or a bad odor.
- The softener has sat unused, for example after a long absence. See vacation mode.
- It is time for routine care. Quality Water Treatment suggests a bleach treatment every 6 to 12 months.
On a septic system, keep sanitizing to what your manual calls for. The WQA's septic guidance says to avoid excess bleach and strong disinfectants; our septic guide has more.
Before you start
Find your resin volume. The dose is set per cubic foot of resin. That figure normally appears on the model label or in the manual; Pentair's 5600SXT, for example, is sold with 1.0, 1.5 or 2.0 cu ft of resin.
Work out the dose. Plan on roughly 1 to 2 fluid ounces of plain, unscented household bleach for each cubic foot of resin, following your manual (Pentair's figure is 1.2 fl oz; SoftPro and QWT use about 2 fl oz). Pentair's figure is for 5.25% bleach and polystyrene resin. For a 1.5 cubic foot softener that works out to about 1.8 fl oz on Pentair's figure or about 3 fl oz on the store figure. Pentair also gives about 0.1 oz per cubic foot for 70% calcium hypochlorite as an alternative.
Check the brine tank has water. The bleach must mix into water in the brine well. Pentair says there must be water in the salt tank when you add it.
Gather supplies. Plain unscented household bleach, a measuring cup marked in fluid ounces, gloves and eye protection. Do not mix bleach with vinegar or other cleaners, and do not put vinegar in the brine tank at all.
Sanitizing steps
The steps below combine Pentair's manual and SoftPro's bleach procedure. Where your manual differs, follow it.
- Note the time and settings. You will run a manual regeneration, so check the display shows the correct time of day. On a Fleck 5600SXT you start one by holding Extra Cycle for 5 seconds (see the Fleck 5600SXT manual guide).
- Put the house on bypass. SoftPro says to bypass the softener so bleach does not reach your taps during the cycle.
- Start with a backwash. Pentair's procedure begins by backwashing the softener. On most valves, starting a manual regeneration does this as its first step.
- Add the bleach. Pour the measured dose into the brine well, the tube inside the brine tank, not onto the salt and never into the resin tank. SoftPro is explicit on this point.
- Let the regeneration draw it in. The brine draw pulls the bleach solution through the resin. SoftPro and QWT both aim for at least one hour of contact time. A manual regeneration takes 60 to 90 minutes, according to SoftPro.
- Run an extra rinse. SoftPro adds a second rinse, and QWT runs an extra regeneration to flush the bleach out. Run a second manual regeneration if your valve has no separate rinse.
If you are not comfortable with the regeneration controls, read our regeneration guide first.
Rinsing and checking
- Return to service. Turn the bypass back to service slowly.
- Flush a cold tap. SoftPro says to run a cold tap for about 20 minutes, or until there is no chlorine smell.
- Flush the other taps. Briefly run each cold tap in the house. SoftPro's bypass guidance is to run cold taps for a few minutes before using hot-water appliances after a bypass change.
- Retest after a few days. SoftPro suggests retesting in 5 to 7 days. If the odor comes back, the cause may be elsewhere, such as the water supply.
- Confirm softening. Check that softened water still tests soft with a hardness test.
Chlorine is one of the things that shortens resin life, which is why the manuals give a measured dose rather than "a splash". Stay within your manual's figure. Keep sanitizing on your regular schedule from the maintenance checklist.
Related guides
Common questions
Can bleach damage softener resin?
The manuals give a measured dose for a reason. Pentair's 1.2 fl oz per cubic foot and the stores' 2 fl oz are small amounts designed for occasional use. Chlorinated city water already wears resin faster, so extra bleach beyond the stated dose is not worth it.
Is it safe to drink the water right after sanitizing?
Keep the softener in bypass until the regeneration and rinse are done, then flush a cold tap for about 20 minutes as SoftPro advises. Once there is no chlorine smell, normal use can resume.
Does sanitizing fix a rotten-egg smell from every tap?
Only if the smell comes from the softener. If hard-water taps outside the softener also smell, the cause is in the water supply or elsewhere in the plumbing, and sanitizing the softener will not cure it.
Can hydrogen peroxide or a commercial sanitizer replace bleach?
Pentair's manual lists household bleach and calcium hypochlorite. For any other product, follow the product's label and your softener maker's guidance, and do not mix products together.
Should the resin tank be opened to pour bleach in?
No. SoftPro says the bleach goes into the brine tank, never the resin tank. The regeneration carries it through the resin for you.
More help: see our water softener guide.