Skip to content

Well Chlorination – The Process

If you have tested your water and gotten a positive coliform / e.coli test, you have ruled out the issues that I have discussed in my “Now what??” article, AND you have collected the information in my “Well Chlorination 101” article, you are ready to consider attempting to do this process yourself. Anyone who is reasonably handy with a tool can do this, but some people may not want to risk creating expensive damage that they don’t want to have to fix. There is that risk – as there is with many home improvement projects.

Please be aware that I am making the assumption that you want to chlorinate the well AND the house piping. Our belief is that if you have only chlorinated the well piping, then the job is only half-done and any bacterial contamination has an even chance of coming back. Most well drillers will only chlorinate the well and will NOT touch the house piping. So, be sure to understand exactly what is being chlorinated and YOU decide if that is sufficient to your needs.

What I have indicated below is a GENERAL discussion only. The detail is explicitly listed out in our well chlorination kit that is available for $69.95 plus tax. If you try to use the following information as an actual procedure, you will need some plumbing and electrical knowledge and some additional supplies to accomplish this without substantially damaging your appliances. You will also be without drinkable water for the entire procedure, so be sure to have sufficient bottled water on hand to drink and an alternate location to shower for the duration.

The first part of the chlorination starts with draining the water heater and the pressure tank. The draining may be difficult to do in an older home or a house with untreated, hard water that has calcium or other deposits in the water heater. If this is difficult to do, then you may want to consider replacing the water heater completely – in which case, you have already made a start on the replacement by draining the old water heater down.

You will need to bypass any water treatment equipment and remove any filter cartridges during this process. After the well is flushed (see below), you will need to disinfect the water treatment system according to the manufacturer’s suggestions and install new filter cartridges and O-rings. This is very important as chlorine can damage water treatment media.

While the water heater is draining, you will need to add chlorine to the well. One method uses a combination of pellets and granulated chlorine because the pellets fall to the bottom of the well to dissolve and the granulated chlorine dissolves on the top of the water column – chlorinating the well from the top and from the bottom. The second method involves dissolving the pellets/granulated chlorine into water and pouring the highly chlorinated water into the water column. We generally do not use bleach to chlorinate a well because liquid bleach is less stable (it loses its efficiency faster).

Once you have done this, then you will need to circulate the water that is in the well from the well to the house and back to the well until you test 100 ppm of chlorine at the hose. Be sure to drain and flush the pressure tank  several times before bringing the chlorinated water into the house. Fill the water heater with chlorinated water, then fill the water lines within the house. Once you have 100 ppm of chlorine at all of the faucets, turn off the water at the pressure tank to the house lines and continue recirculating the water to the well for at least two hours – giving the chlorine contact time to do its job.

Once you are ready to start flushing your well, you will need to minimize the amount of chlorinated water that flows into your septic system. It is inevitable that some will get there, but if you are careful there will be less chlorine than what goes into your septic during an afternoon of cleaning the bathroom shower stall / tub / toilet / sink. You will want to have a long enough hose that will stretch from the house to the area that you want to drain the chlorinated water. Please avoid drainage locations that would place the chlorinated water directly into a body of water such as a stream / pond / river. The chlorinated water will also kill vegetation – which can be to your benefit.

Flushing the well can take anywhere from 2 hours to 2 days and more. If you have a low-production well, then you will need to be very careful that you do not burn up your well pump. If the water stops flowing, turn your well pump off at the breaker until the well recovers. If you have iron in the water (ferrous or ferric), the water that comes out will be varying shades of rust. Keep running the water because the chlorine is causing the iron to oxidize and the water will not clear up until the chlorine is gone.

Once the chlorine in the well water is below 1 ppm of chlorine, you can start flushing your house. If your house is valved properly, you should be able to mostly drain the house piping (hot and cold lines AND the water heater) thru a hose at a location at the lowest point in the house. If you do not have the proper valving, then the job is still doable, but a bit more difficult.

Anytime that you create this much disturbance in an old house’s plumbing system, you are likely to find other problems that were not critical, but may become immediate problems – such as needing to replace a water heater or a pressure tank, faucets that won’t shut off, leaky pipes / joints, or valves that won’t close. These are problems that may require a plumbing service call to fix so budgeting for the additional work to be done at the same time may not be a bad idea.

Once you have completed the flushing and your well water has less than 1 ppm of chlorine in it, we suggest that you re-test your well water for bacteria approximately a week or more later. This will give you a good indicator whether or not your well chlorination is a success. If you get a clean result, then we suggest that you re-test at six months. If you get another clean result, then once a year. However, if something in the well changes (well pump or pitless adaptor is replaced, blasting is done nearby, extended drought, extended rainy period, flooding around the wellhead, etc), then we would suggest going back and re-testing the water.

If you do not get a clean result from your well chlorination, then two things might be the problem. There was an error in the chlorination or the water source is contaminated. Go back over the specific line items listed on our well chlorination procedure and if there were no major deviations, we would encourage you to install an ultraviolet light on the water line. There are things that you will need to know about UV lights that we talk about in other locations on our website.

Please feel free to call us to discuss the issues in depth.

-Andrea D. Jones
Laboratory Director