Did I disinfect my well or not?

[Dorrough]

We have a deep (400 ft) well, drilled last year. Water has always been crystal clear, but hard. We haven't really used much water until recently installing a shower and toilet (talk about luxury living! big improvement over the last three years). When we first tested the water about a week after it was drilled, it had 120 grains hardness and 11 coliform colonies/100 ml. This spring, one year later, we found out the well had never really been disinfected after drilling - the driller told us to pour a couple cups of bleach down the pipe.

So we downloaded some information online and tried cleaning the well cap, pouring a gallon (diluted) of bleach down the well, attaching a hose to the hydrant by the well and washing the walls down for about 20 minutes. We never did smell bleach coming out of the hose. Is there so much water standing in the well that we never got it to recirculate? Or is there such a high flow rate in the aquifer that the bleach just gets washed away before it can be recirculated?

Anyway, waited a week and took another sample at the hydrant. Hardness is now down to 80, coliform bacteria colonies to 2. So we are wondering: maybe our well water is clean - man, it's so deep - and we are just picking up contamination from the hydrant? Or maybe we didn't fully disinfect the well the second time either? Does anyone have experience disinfecting these very deep wells?

Thanks for all the help!

[valveman]

It depends on how much water is in that 400' well. If the water level is close to the surface, you may have 600 gallons of water standing in the well to chlorinate. If the water level is at 380', then you only have about 30 gallons of water in the well to chlorinate. It shouldn’t flow away in the well if you are recirculating the same water back down the well with the hose. If there are 600 gallons in the well, you may have to circulate for an hour with a 10 GPM pump before you smell anything but, you need to have enough to smell in the first place. However, chlorine that is too strong can eat away metal parts in the system, so don’t put more than you need.

[Gary Slusser]

If you have a sand and gravel screened well, yes the chlorine can exit the well into the aquifer but, one gallon probably wasn't sufficient.

So mix 1.5 gal of regular nonscented bleach in like 5-10 gallons of water and pour it down the well. Then run a hose from the boiler drain valve on teh pressure tank down the well for like 20 minutes and smell water from the hose sprayed into a 5 gal bucket every few minutes during the 20 minutes, to see if you smell bleach. Do not splash the water on you or your clothes or in your eyes. If you don't smell bleach, add another 1/2 gallon dilute it and repeat. Repeat adding more until you smell it or get to 3 gallons down the well, then I wouldn't add more than another half gallon to one gallon.

I've shocked many wells as deep as yours. Bleach is heavier than water and will separate and settle to the bottom of the well. That is why you run the hose, to suck it up and then back down to the pump's inlet. 20 minutes is the minimum contact time to kill bacteria but once you smell bleach you run cold water in the house to every fixture. Do the hydrant too. Then run one hot faucet for like 2 minutes. Then Fill a washing machine Cold/Cold for like a minute. Then every 10-15 minutes you run the cold water only at all faucets and hydrant for 10 seconds and shut off the faucet and go do the next.

Repeat at all cold water faucets every 10-15 minutes for like 2 hours. Then run off the well to get rid of the chlorine and then flush all fixtures of chlorinated water in the house. Wait a week after the last time you smell bleach and retest.

[Dorrough]

Thanks Gary, you are the best. This post should get a sticky note because I am sure other people have the same problems as I do, and the directions we find on most state web sites are not nearly this detailed. I'm keeping my fingers crossed that we can in fact disinfect this well and the water will be clean and not require a sanitizer ...

[99k]

As a general rule, 100ppm of chlorine is sufficient ... 1 gallon of bleach should treat 500 gallons of water. I wouldn't go crazy adding more and more bleach if you still have a problem after this next attempt, you need to address the problem

[master plumber mark]

Immagine that your well pump is sitting in a giant swimming pool down there some 400 feet....

no matter how much bleach you pour down it , over a small amount of time it will dillute into the massive amount of water around it... usually within 24 hours...

as long as you bypass the water softener, generally about two gallons of bleach seems to work fine around here to dis--infect both the well and the plumbing pipes in the water system of your home...


we have had to re-shock wells before with increasing amounts of bleach to kill off everything to pass inspections...

never had a problem.....