Questions & answers on how to shock or disinfect a drinking water well: set No. 4.

These questions & answers on well shocking, disinfection, or chlorination will help troubleshoot the procedure for building owners or service providers who need to disinfect a water well.

This article series explains how to shock a well, when, why, and exactly how to chlorinate a drinking water well.

We provide a table explaining the quantity of bleach needed to disinfect a well, and a table comparing the 3 Common Well Water Disinfectants: Chloramine, Chlorine and Chlorine Dioxide.

Page top sketch illustrating both deep and shallow water well construction and depths is provided courtesy of Carson Dunlop Associates, a Toronto home inspection, education & report writing tool company [ carsondunlop.com ].

Questions & Answers on How to Shock or Chlorinate a Well

Recent questions & answers on how to sanitize a well, posted originally

at WELL CHLORINATION & DISINFECTION - be sure to see the procedures and advice given there.

On 2017-05-03 by Chris - results of well shocking

Preliminary results of a total coliform bacteria test came back positive a week or so *after* that arbitrary half-gallon-of-bleach treatment that DEC recommends.

Water ran clear of the cloudiness I described for a while but kept producing and is still producing black sediment that I'm told is iron.

Cloudiness returned shortly after I collected the sample that tested positive for coliform bacteria. I'm planning to first chlorinate the well with scent-free household bleach in quantities determined according to the procedure you describe here.

The level of the well has been near the surface, as the spring thaw is just ending after two weeks and the ground is snow free but just starting to fall below saturation.

I can't really conclude that the well has a persistent source of bacterial contamination until I chlorinate it correctly, so that's what I plan to do first. I'm still suspicious that the saturated groundwater causes surface contamination of the well, and I need a sanitary well cap.

Thanks again for all the information.

On 2017-04-12 by (mod) - Alaska water well disinfection

Do keep us posted, Chris. What you learn will help other readers.

With due respect to the Alaska DEC's pamphlet on "water purification", those instructions are for small quantity disinfection and by absolutely NO means do they produce "pure" water that could be assured to be free of all contaminants or pollutants.

Disinfecting water addresses specifically bacterial contaminants only.

On 2017-04-12 by (mod) - re-posting advice from Alaska DEC on water purification

RE-posting

I understand now. I was operating on general advice from the Alaska DEC according to this document [Alaska DEC on "water purification], but it makes sense that I would want the amount of bleach to correspond to the amount of water in my well.

After running the water for an hour after letting the bleach sit in the system for a day, the water has returned to its light brown/yellow color. I also noticed some sediment in the bottom of a glass I poured, which of course makes sense since I temporarily removed the sediment filter

I will try running the water again this evening for awhile in an effort to stabilize the water before I test, then let you know what i come up with. Thank you!

 

On 2017-04-11 by (mod) - do I need regular well chlorine treatments?

Chris,

I don't think anyone is suggesting that regular "chloronation" of a well is required in the way that you describe, nor that it would be effective.

If it's necessary to shock a well the quantity of bleach that's needed depends on the volume of water in the well.

Arbitrarily using a half gallon does not procedure that would make me confidence that the water was safe to drink

Color contamination of well water can be from any other variety of sources besides bacterial contamination which would be the target of bleach.

My suggestion is to collect a representative sample of your water and have it analyzed by your local water test lab. Let me know what you're told and we can take it from there.

On 2017-04-11 by Chris

Before shocking my well tonight, I failed to consider that I can't smell anything at all with the cold I currently have. I even tried smelling the bottle of bleach afterward and could not smell it.

That said, after living here for four years without understanding that I should have been treating the well twice a year with a half-gallon of bleach, the problem became apparent when my water turned brown/yellow and changing the whole house sediment filter didn't fix it.

So I poured the half gallon of bleach down the well casing, per Alaska DEC guidelines

. I ran water from the garden hose back down the casing until I heard the well pump kick on a second time.

I flushed the toilet and ran cold water from all faucets until the water turned rusty brown. (Water in back of toilet was a dark, rusty brown as well.)

My question is about the hot water faucets. I ran a 1.5 gpm sink faucet nearest the incoming water until the well pump kicked on to fill the pressure tank three times, but the water is still not nearly as dark rusty brown as it is coming out of the cold water faucets.

Is it safe to say I should run the hot water faucet until it's the same rusty brown as the cold water faucets, which incidentally are all still producing this dark rusty water up to this point? My concern is that I'll flush too much of the bleach without treating. Thank you.

On 2017-03-23 by (mod) - I did a well water treatment 2 days ago and after running all the chlorine out the water is now brown. What should I do?

Jennifer


It's possible that a volume of water that you ran to flush out the bleach or will sanitizer was so great that you've exhausted your well. That can cause the water if the water in the well is causing the sediment pick up.

I would suggest waiting 24 hours, and seeing if the brown clears up. If it does not I would have a sample analyzed by a water test lab. If you do that let me know what you're told and we will think about the next step.

On 2017-03-23 by Jennifer

I did a well water treatment 2 days ago and after running all the chlorine out the water is now brown. What should I do?

On 2017-03-06 by (mod) - When should we re-test our well water?

Quoting from the article WELL CHLORINATION & DISINFECTION

Retest the well water after all the Clorox or chlorine is out of the system and the water has been used for 5-7 days (typical health department guideline) or 7-10 days (my suggestion) after the disinfection.

The longer you wait until the well water retest the more valid will be the results, because you are giving time for a remaining bacterial contaminating colony to reproduce. We elaborate on this point at "When to re-test your well water" below.

On 2017-03-04 by Anonymous

We treated our well 10 days ago I was fixing to test our water & husband told me he smelt bleach 2 days ago but none since. When should we test our well water?

On 2016-12-15 by Sarah-Lee Terrat

After shocking a well, how long do you wait until you re-test your water?

On 2016-06-23 by (mod) -

Curious; I'd flush the well to clear water;

On 2016-06-23 by Kieran

The water is 50' deep in a 6' pipe, I used normal household bleach.

When I ran the taps it was smelling so strong I was having trouble breathing, in the morning there was no smell at all. Previous to the treatment the water turned brown and settled into stringy bits at the bottom with an oil like slick on the surface and a smell a bit like battery acid.

The water now turns brown, it settles a little and has a slight film on the surface, it is pretty much as it was only much less severe. Maybe I haven't fully killed it?

On 2016-06-23 by (mod) - I put a gallon of bleach in my well, today there is no chlorine smell

I can't guess Kieran, since we don't know how much water received that gallon of bleach nor the bleach concentration strength. Bleach in water is volatile and will dissipate, but in a well casing, at a quantity sufficient to disinfect, typically you'd smell bleach until flushing the well.

On 2016-06-23 by Kieran

Last night I put a gallon of bleach in my borehole, circulated the water until it was stinking and left it for the night. Today there is absolutely no smell of chlorine, is that normal, does the chlorine evaporate?

On 2016-05-17 by (mod) - how do I disinfect my water heater?

If you are just treating the water heater, and put it on bypass, the other plumbing system components won't be involved nor affected. I'd try that.

Also see the details at WATER TREATMENT EQUIPMENT DISINFECTION

On 2016-05-16 by Anonymous

I have a oil hot water heater which of course is my hot water, (summer winter) do i need to bypass the heater all together and also the water softener, and whole house water filter?

On 2016-05-10 by (mod) - how much chlorine to cure a torten egg smell

Anon:

If the rotten egg smell is due to a temporary bacterial infection of the well follow the tables given at WELL CHLORINATION & DISINFECTION.

The amount of disinfectant needed depends on the volume of water in the well, so there is not one single "right" answer.

if the rotten egg smell is from sulphur in the water supply, shocking the well won't fix the problem.

On 2016-05-10 by Anonymous

How much coring would you put in your well at one time time rid your water of the rotten egg smell

On 2016-04-13 by (mod) -

OK

Indeed plumbing materials are not kept in sterile conditions before they're inserted into a well, that's why SOP is to shock a well after working on it.

If the only contaminant source was one introduced by working on the well

1. it should be cured by proper well shocking procedure

2. it would be odd for that to be causing a dead animal smell

On 2016-04-13 by Kathy

Yes we have been happy with the hand pump and it meets our needs but I believe we may have introduced the contaminates when we installed the pipe for hand pump.

The well was capped with no pump when we bought the place. We installed the simple pump ourselves and then had water tested. It was not stinky water that we recall when we were doing this.

We had it tested for sulfate which was 10 mg/L, fluoride, chloride and some other inorganics, also tested metals ( aluminum,calcium, magnesium, manganese, potassium, sodium, and zinc) and then the microbiological which was the total coliforms and e-coli.

Also nitrogen, solids and pH. Solar pump for the simple pump setup will not pump deep enough.

I think we will have to have a professional probably come shock it. I do not know if our Berkey water filter would take care of what we need to be able to drink it without doing something to the well

On 2016-04-13 by (mod) -

OK so the bore depth is 405 ft. and water rises in the bore to a top height of 278 ft from the bottom.

Thank you for the reference to Sunshine Works - I stand CORRECTED: I was mistaken about the limits of hand pumping. According to Sunshine, their hand pump can lift water from depths. Quoting:

"With the standard 24 inch handle, the hand-operated Simple Pump requires very little force to operate and easily pumps 5 gallons per minute from depths to about 200 feet, delivered at normal household water pressure of about 50 psi."

www.sunshineworks.com/stainless-steel-deep-well-hand-pump.htm

Sunshine also provides solar powered pumps.

Keep in mind that the flow rate of any pump, hand or powered, will diminish as the depth is increased.

Good to have no e-coli, but coliform in the well is still not acceptable, and in my opinion it's also a hint that any other contaminants on the ground surface could be in the well, since coliform in wells most-often gets there from surface runoff entering the well or its aquifer. If you only tested for "bacteria" you might find just coliform but you're not testing for other things like sulphur.

So we have two concerns: bacteria and odor. You might check with your test lab to cover just what was the scope of testing you had done, and whether the lab can test for common odor sources like sulphur or iron-loving bacteria.

Have you also inspected the well and well cap to convince yourselves no critter fell in?

On 2016-04-13 by Kathy

We actually purchased a simple pump from Sunshine Works - the pipe drops down about 325'. According to well log, static water level was 278'. Total depth is 405' not 465' I stated earlier. We had water tested and the only concern was coliforms present per 100ml - no e-coli. The pH is 7.3.

On 2016-04-13 by (mod) -

Kathy:

Thoughts on smells in water in an off-grid water well.

Stinky well water may be due to any of a variety of causes: sulphur, a dead animal, iron-loving bacteria, something else. Start by having your water tested for common contaminants; otherwise one cannot possibly know what are the hazards of, nor the remedies for smelly drinking water.

As you can read in WELL CHLORINATION & DISINFECTION, you will need to calculate the proper amount of bleach to properly and safely sanitize a well. Doing a half-baked guess increases the risk of either illness from bacteria or trouble getting rid of excess chlorine in the system.

Your water filter itself can become contaminated and serve as an odor or bacteria reservoir.

Although your well is 465ft deep, you cannot possibly be pumping by hand from that depth. A hand pump cannot lift water more than about 25 feet.

It does sound as if the pump is working well enough for you to deliver water. But if you are only drawing from the top 25 ft. or so of a deep well and you chlorinate the well using normal means, it may be difficult to remove the chlorinated water as circulation and mixing of chlorine between the bottom 440 ft and the to 25 ft.of water

(IF the water column in your well is really of that depth) will be virtually nil.

Search InspectApedia.com for WELL STATIC HEAD to read about the column of water in a well and its relation to the well bottom and ground surface.

If I were in an off grid property with a deep well I'd consider a solar-operated well pump system, and if my testing and well shocking found a water quality problem (bacteria, smell, other) that needed treatment, I'd add a treatment system.

No simple point of use water filter can handle all contaminants nor high volumes of usage that occur over time.

On 2016-04-12 by Kathy

We have a well on our off-grid property that we installed a hand pump on to get water. We must have introduced some bacteria as it is quite stinky now.

We only are at the property sporadically but would like to Shock it if possible. We have no way to adequately pump the chlorinated water out of the well and am wondering if it will eventually dissipate.

I do have a Berkley water filter that removes chlorine but am just wondering if pouring chlorine down the well without flushing it completely out would be a problem or how long we should wait before we use the water. The well is about 465' deep and we have a deep well hand pump that we use.

It takes about 13 strokes to get water and probably about 20-25 strokes for a gallon of water.

...

Continue reading at WELL CHLORINATION & DISINFECTION or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see WELL DISINFECTION FAQs-5 - more-recent questions and answers about solving problems when or after shocking a well

WELL CLEANING PROCEDURES to address clogged well screens, blocked foot valves, or debris in the well bore.

Or see these

Recommended Articles

• WATER WELL SAFETY & SANITATION, 6 STEPS-EPA
• WELL CHLORINATION & DISINFECTION
• WELL CLEANING PROCEDURES to address clogged well screens, blocked foot valves, or debris in the well bore.
• WELL DISINFECTION PROCEDURE, POST FLOODING
• WELL CONSTRUCTION INFORMATION SOURCES

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