FWIW . . . here is a great video, very simple, that does step by step instructions on how to disinfect a well. Honestly the best one I have seen. It does explain the formula to determine how much bleach to dump down the well, which includes knowing the total depth of the well, the pipe diameter, and the water level where the pump is located.
Safe, step-by-step guide to shock-chlorinate a contaminated well: dosage calculations, PPE, flushing, testing, troubleshooting, and when to call a professional.
waterwellowners.com
SANITIZING A WELL:
The well guy who came out to my house told me the water level is 45' but he did not know the depth of the well so he assumed the well was 100' deep because that is fairly common in the county. This company replaced my pump several years ago, so his records shows the depth of the pump, but it is not the same company that drilled the well 32 years ago, which is why he 'assumed' the well's total depth.
FWIW, he came with a test kit, some granulated chemical, which he said is "basically granulated bleach". He also came with a premixed jug, 5 gallons, that smelled like like chlorine bleach and I have a stuffed up nose. He said the jug was the same chemical as the granulated product, just mixed.
Given the amount of 'chlorine smell' and given the fact that I have a bad sense of smell, I would say that the concentration of that jug was probably the equivalent of 2 or maybe 3 gallons of bleach. It was strong smelling!
FIRST, after being assured NO WATER was running in the house, he dumped into the well, a healthy scoop of, granulated bleach chemical. He said some of it will fall past the pump and go all the way to the bottom of the well and dissolve from the bottom up. Said it was the easiest way to make sure the whole water cavity got sanitized.
* There are several brands of this granulated product. Well Safe, Chlor Safe Nuwell, Well Pro, and other brands can be found via a simple Google search. It appears to be more expensive than using a couple gallons of clorox, but if you were doing a lot of wells, it would likely be cheaper to buy BULK granulated product. For consumer use of disinfecting 1 well, it's roughly $30 for a kit of these products which all claim to do basically what the guy told me.
SECOND, we went inside and bypassed the water softener.
This could have been done first, but I met him outside when he pulled into the driveway. It needs to be done BEFORE any internal water is used.
THIRD, we went back out and he poured all 5 gallons of the chlorine liquid into the well. He let the solution sit in the well for about 10 minutes before turning on the outside hose. Apparently some people immediately turn on the hose, and just pump out the chlorine solution. Waiting 5 to 10 minutes allows some of the chlorine to sink down the water column and into the water pocket/aquifer. Then he ran the hose until he got a chlorine smell. At which point he did a chlorine test, using the test kit to confirm chlorine was coming out of the hose.
We then went inside and did the same thing at every sink. Using COLD water, ran the water while COUNTING just until the chlorine smell was obvious. As some faucets are closer and some faucets are farther away, the reason to "count" while running the COLD water is so that you know how much HOT water run. So at a close faucet it might be a count to 5, but at a distant upstairs faucet, the count could be 10, 15 or even 30 depending on your pipes, layout, etc. He said you are trying to draw enough chlorine into your hot water tank to make sure it is chlorinated. FWIW, by the time I got to the upstairs sinks, showers, I could actually smell some chlorine coming out of the hot water, but it was clearly a milder smell due to the fact that it was diluted with water in my hot water heater's tank.
FOURTH. Today, 24 hours since he departed, I get to flush out the whole system.
He suggested that 1 check my whole house filter to make sure it is clean. Mine is literally a few days old so it is clean. He said the water during the FLUSH period may be dark, may be dirty, the chemical often knocks iron, minerals, etc off of the various parts well column, pump, etc. So I should flush the system, STARTING with the
outside hose until there is no smell. Then as I flush the HOUSE pipes, but this is when it is important to double check the whole house filter. It may, or may not have to be changed during the flushing process.
At this point re-open the flow to the water softener, this will allow some of the chlorine water to run through the softener BUT he said you don't want to leave chlorinated water in the softener which is why you keep it in BYPASS when you start the process of putting chlorinated water into the pipes. The softer resin does not like long term contact with chlorine. But you need to pass chlorine thru the system so when you do the whole house flush you open the system, which allows the softener to also be sanitized.
* There are also softer sanitizing products you can buy separately, which you dump into your brine tube in your salt tank. Then run your system.
Finish flushing out the entire system. He said it's usually about 2+ hours for larger size home, especially with a large water heater tank
(mine is 80 gallons) and more than 3 bathrooms. Looking to get rid of all the visibly dark/black water from the entire system.
FIFTH. Change the whole house filter and start with a fresh filter. So to do it correctly you start with a clean filter, you may clog that filter, you may/may not have to replace that filter mid-flush. Maybe more than 1 time? But it all depends on your well. Then, no matter what, he said start again with a new filter. Simply put, you are going to use a minimum of 2 filters. One at the start, one at the end. Possibly 1 or more in the middle.
Theoretically the water is now safe to drink.