By ion exchange. The tank holds 2.0 cubic feet of ResinTech SIR-100-HP, a nitrate-selective anion resin. As water flows through it, the resin swaps chloride for nitrate and holds the nitrate. When the Fleck valve has counted enough gallons, it rinses the resin with salt brine, sends the nitrate down the drain and readies the resin again. It works like a water softener, with a resin made for nitrate instead of hardness.

On calls I tell people to expect the nitrate to come out completely, and to test the treated water after it goes in so you see it on a lab report.

The 48,000 grain filter, 1.5 cubic feet of resin in a 10 x 54 inch tank, is the nitrate filter I recommend most, including for homes with 4 to 6 people and 3 or 4 bathrooms. The 64,000 grain filter holds 2.0 cubic feet, a third more resin, and handles high flow rates up to 15 gallons per minute; it goes longer between regenerations, so it also makes sense when nitrate or sulfate runs high. Send me your water test and how many people and bathrooms you have, and I'll tell you which one fits.

If your water is hard, yes. Hardness and iron have to come out before the water reaches the nitrate resin, and on hard water the brine and rinse water should be softened too (ResinTech). The order is a sediment filter, then the softener, then this filter, and a UV light last if the well has bacteria. With low pH or iron, I set where the neutralizer or iron filter goes from your test. See our water softeners.

Yes. Nitrite is also an anion and the same resin takes it out. The EPA limits are 10 ppm for nitrate and 1 ppm for nitrite, both measured as nitrogen. Test for both before and after the install.

Not for nitrate, if this filter is treating the whole house. An under-sink RO treats one faucet, the kitchen sink, and I tell nitrate callers to expect it to take out about half, up to 70 percent, so at 20 ppm the RO water can still be at the limit. If you only need drinking and cooking water, the Pure-75 RO is $595; test the RO water after it goes in. With a baby under 6 months in the house, Minnesota's health department recommends bottled water for the baby even with treatment, in case the treatment fails.

The Vortech tank (empty), 2.0 cubic feet of nitrate resin in separate bags or boxes, a fill funnel, the Fleck 5600SXT valve with the bypass pre-installed on it, and the brine tank. The resin is loaded into the tank at install. It ships unassembled and can arrive in more than one shipment. Drain tubing, fittings and salt are not included.

We recommend one. It installs like a water softener: an inlet, an outlet, a 1/2 inch drain line with an air gap, a brine line and an outlet for the valve, and the drain line is the part that takes planning. Plan on about 2 to 3 hours of a plumber's time. I support your plumber by phone at 800-460-5810. If you'd rather do it yourself, you can; text me at 443-277-2204 with any questions.

It uses pellet salt the way a softener does, drawn from the brine tank each time it regenerates. Use plain pellet salt, not rock salt; a 40 lb bag is about $8. How often it regenerates depends on your nitrate, your sulfate and how much water you use, so send me your test and I'll give you an estimate.

Sulfate takes up room on any nitrate resin. SIR-100-HP is made to prefer nitrate, so it will not release captured nitrate back into the water the way generic anion resins can, but high sulfate still means it regenerates more often. If your report shows high sulfate, call or text me the numbers before you order.

I tell callers the nitrate resin lasts about 10 to 15 years. It is rinsed with salt every cycle instead of being used up. If nitrate shows up in your treated water, call or text me first so we can check the salt, the valve settings and the bypass. If those are right, you rebed the tank with replacement SIR-100-HP ($545 per cubic foot) rather than replacing the system.

Yes. Nitrate has no color, taste or smell, so only a test gives you the number, and I size this filter from nitrate, nitrite, sulfate, hardness and iron. Our $199 well water test covers all of them; the $139 nitrate test gives the nitrate number only. The EPA says to test a private well for nitrate every year. If you already have a report, send it to me.

New, unopened and uninstalled equipment can be returned within 30 days of delivery, with our approval first: call 800-460-5810 before you send anything back. A 25% restocking fee applies (waived on an exchange of equal or greater value), and you pay the return freight. Full terms are in our Refund Policy.