Guide to Chlorinating Your Well

If you are a well owner someday you will want to disinfect or chlorinate your well. The most common reason is because coliform bacteria was found in the well water. But there are other reasons:

• the well is new
• the well has been repaired
• the well has been flooded
• the well exposed to bacterial contamination in another manner, such as a crack in the well cap  

Chlorination properly done can not only disinfect, but also rehabilitate the well. As a water well ages, the rate at which water can be pumped (commonly referred to as the well yield) tends to fall. This can be caused by:

• Incrustation from mineral deposits (including iron and manganese) or 
• Bio-fouling by iron bacteria

You disinfect a well and plumbing system by circulating a concentrated chlorine solution throughout the system. The level of chlorine to use is between 100 ppm and 600 ppm (parts per million) depending on your intended purpose and which University extension office is asked. To disinfect a well, I use 200 ppm as recommended by the Virginia Cooperative Extension. On my own well I typically use about 400 ppm or more, about twice what is recommended by the Extension because I am always pushing back the iron bacteria problem in which case a much higher concentration of chlorine is necessary. Be aware that too concentrated a solution or too weak a solution will not be effective.

There are no drinking water standards for iron bacteria so water is very rarely tested for it. Confirmation is usually based on visual symptoms in the water, including the slimy brown/red appearance (often most noticeable in the toilet tank) and an unpleasant musty odor. Over time as iron bacteria takes over the system the perceived quality of the well water declines as iron bacteria produce unpleasant tastes and odors commonly reported as: "swampy," "oily or petroleum," "cucumber," "sewage," "rotten vegetation," or "musty."

The iron bacteria usually discolor the water causing a slight yellow, orange, red or brown tint to the water. The standard protocol for treating iron bacteria is to chlorine shock the well at a recommended chlorine concentration of 500-1,000 parts per million unless the well is already fouled then the pumping equipment in the well must be removed and cleaned, which is usually a job for a well contractor or pump installer.

I have had iron bacteria problems and coliform bacteria in the past. I chlorine shock my well every few years simply to maintain water quality and knock back the iron bacteria. This practice was until recently fairly radical in the private well sector, but is common in small public supply wells and is currently recommended by the Pennsylvania extension and Canadian Provinces.

Two weeks ago I chlorine shocked my well to push back the iron bacteria that was starting to build up in the toilet tank.  Given my arthritic hands I am fairly useless with a wrench, but I borrowed my husband’s ratchet set . Here is how you do it:

First you need to know how deep your well is to calculate how much chlorine to use. Also, the flow rate on the well will give you an idea on how long it will take to clear the well of chlorine. Get a copy of the Well Completion Report from the county. They will make a copy for you, but if you ask nicely they will just email it to you saving you a trip to the department of Health.

Depth of well tells you how much water is stored in the well boring. The typical 6 inch diameter well stores 1.47 gallons per foot, so you multiply your well depth by 1.47 and then add about 110 gallons for the hot water heater and household plumbing . You will need about 3 pints of chlorine per 100 gallons. If you have a very large hot water heater and lots of treatment equipment you will need to add another half a gallon of chlorine. Buy extra- you might need it.

A few days before disinfecting your well you need to purchase all your supplies. You will need:

• a plastic tarp or several green trash bags, 
• 3 -5 gallons of plain unscented Clorox bleach (you need 3 pints for every 100 gallons of water with standard bleach to reach 200 ppm), 
• an 8” diameter funnel, 
• rubber gloves
• a relatively new scrub brush 
• a white 3 gallon bucket (I can’t easily lift a 5 gallon filled with water and chlorine and trying to is how I ruined several pair of pants over the years), 
• lots of chlorine test strips sold for swimming pools 
• a clean and relatively new hose or hoses at least long enough to reach the well from the spigot
• a pair of safety glasses or goggles or sun glasses (don’t want any of those chlorine splashes in your eyes)

In addition, you will want to purchase 10 gallons (or more) of bottled water (to carry you while we have no water to use and make sure that your coffee and tea do not have any chlorine residue to spoil the taste), new refrigerator filters, and coliform home test kits for use in a couple of weeks.

When you are ready to disinfect your well, you need to have about 24-30 hours when you will not be able to use the water. Shock chlorinating a water supply system can potentially damage  pressure tanks, water softeners, filters and filter media, and other treatment devices, but the only way to kill the bacteria is to run the chlorinated water into the components and let it sit in the system. Virginia Cooperative Extension always recommends that you check with component manufacturers before shock chlorinating your water supply system to determine how to bypass or protect this equipment if necessary. With my components I consider this wear and tear. 

Before I begin, I put on old clothes and grab my cheap sun glasses, fill a couple of bathtubs with water that I will use to flush the toilets, then I fill my bucket with some water and chlorine leaving them outside by the well and go into the basement and turn off the power to the well. Then turn off the power or gas to the hot water heater and drain it, and close the water intake valve. (Note, that you need to open a faucet to burp the hot water heater to drain it.) Once the well is fully chlorinated you will refill the hot water heater, but keep it cold (and turned off) during the hold time. Hot chlorinated water is dangerous. Don’t do it.

Now it is time to unbolt and remove the well cap. Examine the well cap to make sure it is in good condition and the screen on the base is sound. Next take your brush and clean off the well cap using the chlorinated water from your bucket. Once the well cap is good and clean place it on the plastic tarp or wrap it in a clean plastic bag. Next scrub the edge of the well casing to remove any dirt and take a rag dipped in chlorine water and wipe down the wires in the well examining them for any damage. Get the wiring nice and clean and push them aside.

• Run your nice new hoses from the house to the well and place on the tarp
• Fill bucket with half water and half chlorine. 
• Turn off power to the well
• Drain the hot water tank and turn off power and close the valve.
• Remove well cap
• Clean well cap with chlorine and water solution and place in clean plastic bag
• Clean well casing top and well cap base using brush dipped in chlorine water
• Pull wires in the well aside if they are blocking the top of the well and clean them with a rag dipped in chlorine water mixture. Make sure there are no nicks or cuts in the wires. 
• Put the funnel in the well top and pour in the chlorine and water mixture
• Now pour in the rest of the chlorine SLOWLY to minimize splashing
• Go back to the basement and turn the power to the well back on (the well is still open).
• Turn on the hose and put it in the well 
• Sit down and wait for a couple of hours

recirculating the water to mix the chlorine- just put the hose in the well

What you are doing is recirculating the water. It is running from the bottom of the well to the pressure tank to the hose into the top of the well and back again. This effectively is mixing the chlorine into the well water. The deeper your well the longer this takes. Also, if you have any treatment tanks installed ahead of the pressure tank they are also being included in this cycle. After a couple of hours the water should look orange and test strongly for chlorine. 

when the chlorine is mixed you will see brown water 

 Special note: If you have an older well and you have never chlorinated it, the mixing of the chlorine and water is going to not only turn orange or brown, but also bring up all the gunk that had accumulated in your well. During well disinfection, free chlorine is introduced into the well water; an adequate amount of chlorine will flush the mineral build up, iron in solution in the water and reducing bacteria out of the well. There could be a lot more than a gentle brown tinge and you might want to consider running off the water for a couple of hours and adding more chlorine then recirculating again. I did that the first time I chlorinated my well. I did not want all that orange gunk in my plumbing. Also, the oxidizing all that gunk consumes the chlorine, so make sure that your final concentration of chlorine is 200 ppm and before you seal up the well: 

• Use the hose to wash down the inside of the well casing
• Turn off the hose
• Carefully bolt the well cap back in place
• Fill your hot water heater with water (keep it turned off)
• Draw water to every faucet in the house until it tests positive for chlorine then flush all your toilets. Turn off your ice maker. 
• Then it is no water for 12-24 hours 
• Set up your hoses to run to a gravel area or non-sensitive drainage area. The chlorine will damage plants.

After 16 hours turn on the hoses leave them to run for the next 12-24 hours unless your recharge rate is low enough to run your well dry. In that case let the well recharge for hours between flushings. The time is dependent on the depth of the well and the recharge rate. Deeper wells with a faster recharge rate take a long time because you cannot run your well dry-it recharges faster than I can pump so the chlorine just keeps diluting.

After about 12 hours of running the hoses begin testing the water coming out of the hose for chlorine. Keep running the hose and testing the chlorine until the water runs clear and chlorine tests below about 10 ppm.

• Now it is time to drain the hot water heater again, refill it and turn it back on
• Open each faucet in the house (one at a time) and let run it until the water tested free of chlorine. Be aware the hot water will sputter- big time- until all the air is out of the system. Flush all the toilets
• Dump all your ice and turn your ice maker back on. * I do not change my refrigerator filter for at least another week. I use the filter to remove any traces of chlorine left in there water. There will be some.
• You are done. 

There are a few twists and turns that can come up, remember that you have merely poured an oxidizing agent into the well. Ultimately, it will flush out along with all the iron, mineral buildup, reducing bacteria gunk, etc.  If you have treatment tanks in your basement, you also want to drain them after the chlorine has been flushed out of the system. Do not drain them into your septic system. Good luck.