What to do if your water tests positive

If you’ve recently done a water sample on your well and the results came back positive, here’s what you do next.

First of all, which test came back positive? If it was a bacteriological sample (bacti or Bac-T), read on. If it was another sample, skip ahead to learn more.

Bacteriological Sample Positive Result

What it looks like:  You receive the lab report, and under the “Sample Result” field it lists the word “PRESENT”.

What that means: Most of the time, a potability test on your well is testing for microorganisims that could cause illness. The “Total Coliform” test is checking to see if there are marker bacteria in the water, which would indicate that contamination is entering your well or water system. The “E. Coli” test is checking for the Eschericia coli bacteria, which can cause illness.

What can be done about it:  If you’re trying to sell your house, and the water has bacteria in it, you’ll need to make the buyer aware. You can probably expect to have to clean up the well, in order to make sure the water is potable. According to the Idaho Department of Environmental Quality, your private well is your responsibility to maintain.

Your options:

  • Hire us to clean up the well for you.  This involves three trips onsite – one to add high-strength disinfectant to the well, a second trip to flush the system out, then a third trip 48 hours after the flush to collect another bacti sample.
  • Treat it yourself.  You can dump a gallon of chlorine bleach down your well, followed by a gallon of water.  Turn the water on in the house till you smell chlorine, then let the water sit for 6-8 hours.  (Overnight is fine.)  After it sets, turn on all the water faucets and let them run until you don’t smell chlorine anymore.
  • Boil your water.  In the short term, boiling the water can kill bacteria and make your water safe to drink.  YOu can also get water filters that can clean out the bacteria.
  • If these don’t work:  We can rechlorinate and test again.  Sometimes, if there’s a problem in the aquifer or the well (such as mice falling down a hole in the well seal), disinfectant just doesn’t clear things up.  This might require a well drill to blow air down the well to try to clean out any material.  A contaminated well may even need to be replaced.

Nitrate Sample

What it looks like:  On your lab report, there’s a number in the results column for Nitrate.  It will usually look like 4.36 mg/L (milligrams per liter) or something similar.  1 milligram per liter is equal to 1 part per million (ppm).

What it means:  Nitrate, or NO3, is a chemical that’s found along with agriculture.  Dairies might produce nitrates in the form of animal waste, or farms might produce nitrates in the form of fertilizer.  When it rains, those nitrates can leach down through the ground, or can be washed down a poorly-sealed well.  According to the EPA, anything below 10 mg/L is not actionable.  So you may have nitrates in your water, but they probably won’t affect you unless the number is higher than 10.

If your water sample is higher than 10 mg/L, you’ll want to treat your water to reduce the nitrate levels.  Too much nitrate in the water can cause health problems, especially in infants and the elderly.

What can be done about it:  Boiling your water or running it through a filter won’t remove nitrates from your water.  You’ll want to look at installing treatment equipment as well.  An RO system (Reverse Osmosis) would work.  There are also devices that work like a water softener, which can remove nitrate from your water.

Typically, the EPA does not regulate Nitrate for private domestic wells.  So it’s not against the law for your private well to have a high Nitrate level.  However, if you’re on a public water system, the EPA does require that the water contain less than 10 mg/L Nitrate.  Some lenders will stipulate to the EPA limits if you’re buying, selling, or refinancing a home, so you may need to treat the water for a sale to go through.

Your options:

  • Consult your doctor, and have a conversation about how the levels of nitrate in your water can affect your health, and your family’s health.
  • Invest in a treatment system.


What it looks like:  The symbol for Arsenic is As, and it can be highly toxic in high concentrations.  Several small towns in Southern Idaho have tested high in Arsenic, and have had to spend a lot of money on treatment equipment to make the water safe to drink.  The EPA limit on Arsenic is 0.010 mg/L, which is equal to 10 parts per billion.  (With a B.)

What it means:  Arsenic is a naturally-occuring substance in the rocks underground.  Unfortunately, some places in Idaho just have deposits of Arsenic that formed when the rocks were cooling, and there’s not much to be done about it.  Some forms of Arsenic were used in pesticides, but most of those have been banned.  It may linger in the soil, or in old stockpiles of chemicals, so be careful.  Arsenic can be highly toxic, and can cause certain kinds of cancer.  You can read more about arsenic in groundwater here, (but please disregard the state-specific information).

What can be done about it:  Boiling your water won’t help.  It’s just like adding salt to water – you can boil it all day long, and it stays salty.  If the concentration of arsenic in your water is high, you’ll probably want to look at installing treatment equipment, much like Nitrate above.  Using a Reverse-Osmosis (RO) system can help, or an Arsenic reduction system that works like a water softener.  Make sure you keep the equipment maintained, by checking it or having it serviced yearly.

Your options:

  • Install treatment equipment, like an ion-exchange unit or a Reverse Osmosis unit
  • Consider drilling a new well, and consult with your well driller on a good location, and whether any arsenic-bearing deposits can be isolated by installing casing


What it looks like:  The symbol for Lead is “Pb,” and it can be hazardous in high concentrations.    The EPA limit for Lead is 0.015 mg/L, though in public water systems the sample is averaged over several sample locations.  Any lead results that are higher than 0.015 mg/L – or 15 parts per billion – can be hazardous to your health, especially to the brain development of children.

What it means:  Typically, Lead gets into the water from old pipes and older brass pipe fittings.  Most modern plumbing has eliminated lead in the manufacturing process.  Also, the groundwater in Idaho has a lot of hardness, which we see as white spots or buildup on faucets.  This hardness tends to accumulate in pipes, reducing the odds that lead can get into the water.

What can be done about it:  If you’ve got an older home, you should consider replacing the plumbing and faucets in your house, at least the ones you drink out of.  You can also install treatment equipment, such as a Reverse Osmosis system to reduce the levels of Lead.