Well Disinfection?

[Bradsky]

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?

[Mr.Whyso]

I don't but good luck. Sounds like a serous may need to call a plumber issue. The only problem I see is how could a gallon of dilluted bleach disenfect a 400 ft well? I just don't know.

[bradthebard]

Last well I had dug we ran it for something like ten hours after shocking it with chlorine. It was a 750' well, so it needed a bit more time but I would say 20 minutes probably wasn't enough. On the other hand, if it cleared it up, good on ya!

[speedbump]

More bleach may be in order. For a 400 foot well, I would use about 5 gallons of bleach (unscented) and a bag of Sodium Hypochlorite. The Sodium Hypochlorite will dissolve slowly and keep bleaching after the liquid bleach is long gone.

After pouring the bleach down the well, rinse the walls of the casing with at least 10 gallons of fresh water to wash all the bleach off the pipe, wire etc. Run water in the building until bleach is smelled in each faucet (cold only) then let sit for at least 4 hours. Over night is better. Then flush until clear. Wait a few weeks and take another sample.

One thing about sampling: Be sure to disinfect the faucet to be sampled from with alcohol, let run for ten minutes, then be very careful with the sample bag so as not to touch the inside parts of the bag with your hands. They have more germs on them than the well ever did.

Good luck.

[Nuthin]

The thing about bleach is: you don't need much and it's way heavier than water so it all settles to the bottom. If you're pumping from above the bleach, you'll likely never smell it.

[Driller1]

The stuff we use is 90% chlorine. Much stronger than bleach.

That being said, the best thing to get a clean BT test is to pump it. I like to let them pump three days straight before we try a test.

Do you have a sample tap on your pressure tank? If so, take the test from there. Be sure and flame the tap/hydrant before taking the sample.