How Long Does it Take to Get Chlorine out of Well Water?

Shock chlorination is a common practice used to prevent the build-up of bacteria and viruses in homes on well water.

Wells may be shock chlorinated if they become contaminated due to runoff from a storm or flood, when there’s a contamination event in the local environment, or after fixing a crack in a well casing or lid.

This type of disinfection involves circulating large amounts of chlorine through a well and pumping it up the well pipe, throughout a home’s plumbing, faucets, and fixtures.

Because the amount of chlorine used during well shock chlorination is much higher than the levels regularly used to disinfect city water, it may not be safe to drink or use water from a freshly chlorinated well.

You may also notice a strong chemical smell coming from your faucets after shock chlorination.

Illustration of Chlorine element and bottle

So how long does it take for the shock chlorination process to finish, and when can you safely return to consuming and using your well water?

How long does it take to for chlorine to leave your plumbing after shock chlorination?

Once the chlorine has been circulated through a well the flushing process has begun, it will take between an hour and an entire day for all of the chlorine to leave the well. The wide discrepancy between times is due to the many differences between individual wells—mostly their depth. A very shallow well can flush in as little as 30 minutes, while deep wells can take up to 24 hours.

During shock chlorination, the chlorine will also pass through a home's entire plumbing system. Most plumbers will turn on every faucet and fixture until chlorinated water runs out, before turning them off to let the chlorine sit in contact with that part of the system.

Once the chlorine smell has vanished from the well and the appropriate amount of contact time has passed, you'll need to begin opening each faucet in your home and running water until the chlorine smell has dissipated This process should only take a matter of minutes if done correctly.

Sometimes, it will be necessary to run the hot water faucets for much longer than the cold ones. It's also possible that you'll need to drain the water heater as well.

How long should you wait to use water after you chlorinate a well?

As said above, it might take anything from 30 minutes to 24 hours to remove all of the chlorine from a well. After that, you'll need to wait a little longer to ensure that chlorine has had enough time to circulate and flush from your home's plumbing.

Once the process is finished, check each faucet to make sure there is no longer any chemical scent. Don't forget outside faucets and showers.

According to the CDC, safe chlorine limits in drinking water max out at 4mg per liter. At this concentration, water will have none or very faint chlorine odors, so a smell test is normally sufficient to judge.

The most accurate way to check your chlorine levels is with test strips, which can be bought from any large hardware store.

If you or your family are particularly sensitive to chlorinated water, it may be advisable to avoid taking long showers or baths for a few days after shock chlorination.

With a chlorinated well, we recommend waiting at least 24 hours after the entire chlorination process (including flushing) is complete before you do any sensitive task—for example, doing delicate laundry or bathing youngsters.

Adding this time buffer is an especially good idea if you don't have chlorine test strips.

Test your well water to determine when you can resume normal use

One or two weeks after chlorination, it's important to retest your well water for coliform bacteria.

The water is safe to drink if the tests confirm that coliform bacteria are absent. This is the true date at which you can resume normal use of your well water.

Until you have your water re-tested, it's safest to assume that some contamination remains. Practice safe habits such as boiling or correctly filtering water before drinking. Here's a list of our favorite well water filtration systems for more on that.

A licensed well driller/contractor can recommend a continuous disinfection treatment system if test results show that shock chlorination had no effect on coliform bacteria in the water.

5 Well water chlorination Don'ts:

  • Chlorine can create a strong burning sensation in the eyes and irritate the skin. Be careful when handling chlorinated water or standing near a well undergoing shock chlorination.
  • Don't forget to inform all members of your household that your water is undergoing chlorination treatment. Drinking water that has just been shock-chlorinated can result in serious illness or death.
  • A smell test to check for chlorine levels is good, but don't forget that chlorine test strips are accurate, widely available, and relatively cheap.
  • Gardens, wildlife, and septic tanks can be damaged by highly chlorinated water. Don't flush your well onto lawns or flower beds, near tanks, or into waterways that lead to aquatic ecosystems.
  • You must test your well after shock chlorination to check whether bacteria have returned. Do not assume that the treatment was effective.