How to clean iron out of softener resin

Best for

Well owners whose softener has slowly lost capacity or started passing iron stains, on water with modest dissolved iron.

Wrong fit

If the water comes out of the well already orange, has iron bacteria slime, or has iron well above the softener's rating, cleaning resin only buys time. Treat the iron before the softener.

Tradeoff

An ongoing resin cleaner is cheap and needs no extra tank, but it is one more product to keep stocked. An iron filter costs more and needs its own drain and power, but keeps iron off the resin.

Signs your resin is iron-fouled

Iron fouling builds up slowly, so the signs are easy to miss at first:

• The softener has salt and the settings are right, but soft water runs out before the next regeneration.
• Hardness creeps back at the tap a few weeks or months after install, then gets steadily worse.
• Orange or rust staining returns in toilets, tubs and laundry.
• The softener seems to regenerate normally but the water never tests fully soft.

Nebraska Extension notes that high concentrations of iron or manganese can affect the resin’s exchange capacity, and that the resin may eventually need to be cleaned or replaced.

Rule out the simple causes first. Check that the bypass valve is closed, the salt has not formed a hard bridge above the water, the brine tank actually has brine, and the hardness setting matches your water (including the iron allowance). See water softener settings. Then test the softened water for hardness and iron. If both are higher than they should be and the simple causes check out, the resin is the likely problem.

Why iron fouls resin

Softener resin can exchange dissolved (ferrous, or clear-water) iron the same way it exchanges calcium and magnesium. Penn State Extension puts the difference plainly: colorless, reduced iron is removed by the unit, but red, oxidized iron, meaning iron that has been exposed to air or chlorine, will clog the resin. Oxidized iron is a particle, not a dissolved ion, and regeneration does not reliably wash it out.

Fouling gets worse when:

• There is more iron than the resin is meant to take. ResinTech’s data sheet for a common softening resin says feedwater iron should be no more than 1 mg/L (ppm) for each 17 mg/L of hardness, or roughly 1 mg/L per grain per gallon. Nebraska Extension says excess iron above 5 mg/L can reduce a softener’s effectiveness.
• The water is not very hard. Virginia Cooperative Extension advises against using a softener to remove iron from naturally soft water.
• Iron bacteria are present. Virginia Cooperative Extension describes the signs: gelatinous slime inside the toilet tank and rusty slugs from the tap. Penn State notes that bacteria and fungi can form mats in resin that reduce its effectiveness.
• Salt settings are very lean. WQA’s best-practice booklet says high-efficiency softeners generally need iron under 2 ppm to reach their salt efficiency ratings.

Manganese causes the same kind of trouble; Nebraska Extension names it alongside iron as a cause of lost exchange capacity.

How to clean the resin

Penn State says that if the resin has already been fouled, commercial cleaners are available, and to check the manufacturer’s instructions for special precautions. The Minnesota Department of Health says that where iron is excessive, an iron removal additive is advisable, and to follow the manufacturer’s instructions.

The general process for a one-time cleaning:

1. Read the softener manual and the cleaner label. Use a product labeled for water softener resin on drinking-water systems. If the manual and the label disagree, ask the softener maker.
2. Make sure there is salt in the brine tank and the softener is in service, not in bypass.
3. Add the cleaner where the label says to, usually into the brine tank or the brine well, in the dose the label gives.
4. Start a manual regeneration so the cleaner is drawn through the resin with the brine.
5. Rinse as the label directs before drinking or cooking with the water.
6. Retest the next day. Softened water should be under 1 gpg (17.1 mg/L) of hardness, with little or no iron.

A heavily fouled bed may need more than one cleaning. If you cannot get hardness down after two or three tries, see the section on replacement below.

Ongoing cleaning. If your well sends iron to the softener every day, a single cleaning will not last. The alternatives are a cleaner added with each regeneration, as its label directs, or softener salt that already contains an iron-removal additive. WQA’s design course recommends that a softener working behind an iron filter be regenerated with a strong brine and a resin cleaning solution, which it says gives an optimum resin bed cleaning and years of trouble-free service.

Bleach is for bacteria, not iron

Bleach does a different job. Penn State says disinfecting the water before softening, or periodically cleaning the softener with chlorine bleach, will deal with bacteria and fungi that form mats in the resin. It also says to read the manufacturer’s instructions before adding any chemical to the unit.

Two cautions:

• Chlorine oxidizes iron. Penn State’s point that iron exposed to chlorine clogs resin applies here. Ask the softener maker whether to clean out iron first and in what order to use each product.
• Iron bacteria live in the well, not just the softener. Virginia Cooperative Extension says high doses of chlorine (200 to 500 mg/L, known as shock chlorination) may be needed periodically to control iron bacteria, and that the treatment must include the well and the pumping system. Bleaching only the softener will not fix a well problem.

Clean the brine tank and check the backwash

Fouled resin often comes with a neglected brine tank:

• Brine tank. The Minnesota Department of Health says to periodically clean and disinfect the brine tank. NDSU Extension says the owner’s manual will usually explain how to clean it with bleach, and that how often depends on how much salt you use and how pure it is.
• Brine valve and float. Nebraska Extension says to clean and inspect them at least once a year.
• Backwash. Nebraska Extension says adequate backwashing is important for efficient regeneration. On a unit with adjustable backwash time, it suggests setting it long enough to produce clear water at the drain. NDSU Extension says more frequent backflushing may be required to remove iron buildup.
• Sediment. Penn State says turbid well water can clog resin with mud and clay, and that normal backwashing sometimes clears it.

When to replace the resin

Penn State says that in some instances resin cannot be washed of contaminants and needs to be replaced, and that this should not be the case if the resin is regularly regenerated and maintained. It suggests consulting your softener dealer about replacement. Nebraska Extension says to consult a water treatment professional for guidance on cleaning or replacing resin.

Replacement makes sense when cleaning no longer restores soft water, or when the resin has been fouled for a long time. Before you rebed, fix the cause, or the new resin will foul the same way.

How to stop it coming back

Work through these in order:

1. Know your iron number. Test raw well water for iron, manganese and hardness, and look at whether the water is clear or orange when it comes out of the tap. Clear water that turns orange on standing is dissolved iron; water already orange or cloudy at the tap is oxidized iron. See iron and water softeners.
2. Compare it with the softener’s rating. Nebraska Extension says softeners may remove as much as 5 to 10 mg/L of iron and manganese, and that you should check the manufacturer’s rating. Published limits vary widely by model.
3. Set the softener for iron. Include the iron allowance in the hardness setting and use a shorter day override so iron does not sit in the resin. See water softener settings.
4. Use a resin cleaner on an ongoing basis if iron is within the softener’s rating but still causes buildup.
5. Put an iron filter first if iron is above what the softener should take, is already oxidized, or comes with manganese or a sulfur smell. Penn State says filtration before softening ensures oxidized iron is not processed in the softener. NDSU says excess iron or hydrogen sulfide can inhibit a softener and iron removal equipment may be required. A whole-house air-injection well water filter is one option; compare it with other setups in iron filter vs water softener and well water filter and softener combo.

If your well has iron bacteria, shock chlorinate the well and retest before buying more equipment.