Water problem
Nitrates
Nitrate enters groundwater from fertiliser, manure, and septic systems. It carries a specific and serious risk for infants under six months, which is why the federal limit is set where it is.
What you might notice
- None. Nitrate is colourless, odourless, and tasteless
- A well in an agricultural area or downgradient of a septic field
- A shallow or older dug well
Why the limit is set where it is
The federal maximum contaminant level for nitrate is 10 milligrams per litre measured as nitrogen. That limit is driven by a specific risk to infants under six months, in whom nitrate interferes with the blood's ability to carry oxygen.
For that reason nitrate is one of the few water quality parameters where the correct response depends on who lives in the house. A result that warrants monitoring in one household warrants immediate action in another.
If there is an infant in the home, or someone is pregnant, do not use water above the limit for drinking or for making formula while you sort out treatment. Use bottled water in the interim.
How it gets into the water
Nitrate reaches groundwater from fertiliser applied to farmland, from manure, and from septic systems. It is highly soluble and moves readily with water through soil, which is why it is one of the most common contaminants found in private wells in agricultural areas.
Shallow wells, older dug wells, and wells with poor casing seals are the most exposed, because they draw from closer to the surface where nitrate concentrations are highest.
Concentrations can vary through the year, rising after heavy rain or after fertiliser application. A single clean test in midwinter is less reassuring than it looks, which is why annual testing at a consistent time is the recommendation.
What does not work, and what does
Boiling makes nitrate worse. Water evaporates and nitrate stays behind, so the concentration rises. This is worth knowing because boiling is many people's instinct for any water worry.
Carbon filters do not remove nitrate. Neither do standard softeners, sediment filters, or ultraviolet systems. A great deal of equipment can be bought that will have no effect at all on this contaminant.
Reverse osmosis certified under NSF/ANSI 58 does remove it, and ion exchange systems designed specifically for nitrate are used where whole-house treatment is needed. If the test is below the limit and there is no infant in the household, routine annual monitoring is the proportionate response rather than equipment.
How to confirm it
A laboratory test. The federal maximum contaminant level is 10 mg/L measured as nitrate-nitrogen. Public systems monitor for it and report it. Private well owners should test annually, and immediately if anyone in the household is pregnant or there is an infant.
The test that settles this is laboratory nitrate-nitrogen analysis. We include what we can measure on site in a free water test, and we will tell you plainly when a certified laboratory is the right next step rather than anything we can do at your kitchen tap.
When not to treat it
Boiling does not reduce nitrate. It concentrates it, so it makes the problem worse. Carbon filters and softeners do not remove it either. If a test shows nitrate below the limit and there is no infant in the household, routine monitoring is the appropriate response rather than equipment.
Treatment options that actually apply
These are the equipment types that address this problem. Each page states what the equipment does not do, so you can rule it out quickly if your situation does not match.
- Reverse osmosis, tank. A membrane system under the sink that produces treated water to a dedicated tap and stores it in a small pressure tank.
- Well water systems. A treatment train assembled around a current laboratory test, in stages.
What none of these will do
- Water at any tap other than the one it feeds. Showers and laundry are untouched.
- Hardness in the rest of the house, so scale continues elsewhere.
- Bacteria, unless the unit is specifically certified for it. Do not treat unsafe water with RO alone.
Getting it installed
Once a test has confirmed the problem and narrowed the equipment, the practical questions are access, space, and whether anyone's permission is needed. Those are covered on the installation pages, along with what a visit involves and how long it takes.
- Free water testing. 45 to 60 minutes.
- All installation services
- What installation costs
Other water problems
Sources
- Nitrate and Nitrite in Drinking Water. US Environmental Protection Agency, 2024.
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