Questions & answers on how to shock or disinfect a drinking water well:

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 2022-12-17 by InspectApedia (Editor) - green water drinking safety?

@Dennis,

Thank you for the "green water drinking safety" question.

I won't bet your health and safety on guessing when we have not a shred of information about your water supply and its chemistry.

Greenish tint in water might be from algae, from copper oxidation or corrosion products (including from new copper plumbing).

I don't assume that the green is what you're calling biomass.

My advice is to take a water sample to your local water testing lab and ask them what tests are appropriate for "green-tinted water" or what packaged collection of tests they recommend.

Bacteria testing, alone, such as you might have had performed when you purchased your home, does not detect any other sorts of water contaminants.

This COLOR OF WATER FACT SHEET [PDF] from the California State Water Resources Control Board may be of help

There are also some less common causes of greenish stuff in water, such as aluminum hydroxide - as discussed at this

ALUMINUM HYDROXIDE in WATER - AO SMITH TECHNICAL BULLETIN

On 2022-12-17 by Dennis

We moved into a house and the owners hadn’t done any maintenance on the well in a couple years, so we had it sanitized. It’s been a couple days, the chlorine/bleach smell is gone but our water is still slightly green.

I’m guessing this is biomass still coming free from the system. I’ve flushed the system at least 3-5 times. Is my water safe to use/drink?

On 2022-07-21 by InspectApedia-911 (mod) - fine air bubbles in water supply

I find air bubbles in the water supply is not likely to have anything directly to do with having shocked the well unless the shocking process left a leaky pipe connection somewhere.

Please use the on-page search box search for the phrase

Fine air bubbles in water supply

And you will see that we have several articles on this topic including the cause of fine air bubbles in hot water, air discharge at fixtures in general, and ways to cure the problem.

If you notice that the fine air bubbles are particularly present in the hot water supply you could go directly to this article

https://inspectapedia.com/water/Air-Discharge-at-Hot-Water-Faucet.php

On 2022-07-21 by diane

We had our well shocked two weeks ago. There is no smell of bleach and chlorine now has tested negative. We have a submersible pump that is only 3 years old along with our water softener system.

Now our water from all our taps is cloudy and there are bubbles in it. It clears quickly in a glass and there isn't any sediments at the bottom. What could cause this and how do I clear this. It's has never been like this.

On 2022-06-16 by InspectApedia-911 (mod) - attempting to disinfect a water system after working on plumbing is a reasonable practice

@David,

Of course knowing nothing about your building, I can't provide an absolutely certain answer,

Attempting to disinfect a water system after working on plumbing is a reasonable practice although I'm not sure that what the plumber did is the best approach.

Nevertheless, it's not likely that what the plumber did has damaged your building plumbing nor the pump.

More likely it was the installation of the new pump combined with a period of no water flowing in the pipes and then suddenly flowing again that stirred and displayed sediment from your piping system.

Can you tell me if pipes in your building are galvanized iron?

On 2022-06-16 by David

Our plumber poured a half gallon of undiluted clorox into our new jet pump to sterilize it during installation. Then about a half hour later, he finally started up the pump to circulate the bleach through the system. A lot of red water and sediment came out of our faucets.

We're worried that the strong bleach may have damaged the pump. Is that possible? Thanks.

On 2021-08-23 by inspectapedia.com.moderator - you have not successfully flushed the well

@Deb,

Sounds like you have not successfully flushed the well.

And why on earth are you using pool shock in a well?

And how did you compute how much disinfectant to use? 1 Gallon sounds arbitrary.

See procedures and proper type and amount of disinfectant to use in a well at

WELL CHLORINATION & DISINFECTION - topic home -

and let me know what questions remain

On 2021-08-22 by Deb

Chlorinated well 1 gallon. When run hot water in tub upstairs it’s light orange. The tub downstairs is grey black looking. I ran all faucets about 10 minutes after 24 he. setting w-pool shock.

On 2021-06-16 by mak.church (mod) - orange water and iron smell is back

@Hillary Middleton, You need to start by having your water tested to ensure that the red stain is coming from the water source and not from algae or bacteria in any of your water treatment equipment. If the stain is from the water source, then when the type of material is identified, such as iron, we will know what treatment is needed.

Let us know if you have additional questions and we'll be interested in hearing the outcome of your testing.

On 2021-06-16 by Hillary Middleton

Hi okay so we've always had really orange water, 2 months ago we got a new softener and the water was great!...that only lasted a few weeks, we thought maybe something caused a bacteria bloom but it wasn't going away,

so about 3 weeks ago we poured 2 gallons of bleach into our well let it sit for a few hours ran the faucets till we smelled it then let it sit again for a few hours, and then ran faucets till we no longer smelled it which took a whole day.

The water clear and felt great in the shower, well starting last week the orange water and iron smell is back full force, it seems to come out clearish but if let to sit it turns really orange ... What is going on? What do we do now?

On 2021-05-12 by danjoefriedman (mod) - poured 1 gallon of bleach into well

@Carla, "1 gallon" may have been arbitrary; to do this right see the procedures described at

Continue reading at WELL CHLORINATION & DISINFECTION

where you'll find a live link - near the end of the article below.

Then you should take a look at the diagnostics at WATER PRESSURE INTERMITTENT LOSS

On 2021-05-10 by Carla

We poured 1 gallon of bleach into well. Ran water and could smell slight bleach. 2 days later water pressure is intermittent and flow stops all together for a few minutes; stronger smell of bleach noticed now than first 2 days. Well pump and bladder are 4 years old .

On 2020-11-22 by Frank

my well is drilled but the head is buried and I want to sanitize it . how do I get the bleach into the well?

On 2020-10-28 by danjoefriedman (mod)

Please See your question and my answer posted at.

https://inspectapedia.com/plumbing/Water-Softener-Sanitize-Resin-Tank.php

On 2020-10-28 by Anonymous

I shocked my well an we ran water till we didnt smelled bleach anymore but now I am smelling it again but just not strong and I did a home test an sayes the chlorine is like 3ppm an I can still smell bleach what to do now

On 2017-08-25 by (mod) - how do I disinfect new plumbing work?

You could simply review the well sanitizing procedure given

at WELL CHLORINATION & DISINFECTION, allowing the bleach solution to sit overnight in the water system to disinfect everything, or you could try to chlorinate the water downstream from the UV system, at a sufficient concentration and for a sufficient time.

Watch out: Beware that if you over-dose the well and then fill a water tank and water heater you may need to drain them during flushing out of the bleach solution.

If I were just sweating in a replacement pipe section in a water supply line I'd probably not worry about it, or if I had a reason for concern I'd find it easier to chlorinate the new pipe before installation.

Chlorination won't harm the UV system.

BUT Watch out: a well water system that has sediment needs filtration and might if the water is hard also need softening - to slow the accumulation of debris on the UV light that will render it ineffective.

Also most UV lights come with instructions recommending an annual replacement of the bulb.

Also, and this is most important, while the "no-e coli" suggests that your well water isn't contaminated with effluent from a sewage or septic system, to me (and your water lab should confirm this view), when we find coliform in a well we know that the most-common source is surface water or surface runoff that is entering the well.

In that case ANY contaminant on the surface (road salt, pesticides, etc) that is or was nearby can be in the well. The coliform test is a high-level screening test. It is absolutely not a guarantee that there are no other contaminants in the well. Further water tests are probably in order.

On 2017-08-24 by mongo

I recently bought a home, well failed for total coliform..no e coli or fecal..sellers to install UV and retest before closing..

I have some simple plumbing repairs to do myself. replace a leaking copper pipe and a galvanized drain line.

.how do I disinfect my work as not to contaminate the system ? also I can have the well chlorinated with the uv system ..with by passing the uv..then put the uv back on line ?? thanks.

On 2017-08-25 by (mod) - chlorine by weight?

Linda: at WELL CHLORINATION & DISINFECTION we give recommended bleach concentrations for this process.

Watch out: though. The simple "depth" of the well is not the key number, it's the height of the water column or the static head (search InspectApedia for WELL STATIC HEAD if that's not a term you know about)., Consider that your well could

be 600 feet deep but just have 30 feet of water in it.

On 2017-08-04 by Linda

How many gallons of 5% sodium hypochlorite will be used to disinfect a well 200 feet deep if the weight of the chlorine is .5 pounds?

On 2017-07-16 by Miriam we are not smelling bleach even though we poured some into the well

We have a 515 ft well. As best we can tell, the water level is 485 feet (we hit water when using a weighed string at 30 feet).

We put approx. 2 gal of household bleach into the well and let the hose at the well house run for over 30 minutes. Still no bleach smell.

Our water pH is between 7 & 7.4. Why can't we smell bleach in the hose yet? Is the pH too high or did we just not put in enough bleach?

We used the amount that was recommended by the University of Tennessee extension office.

On 2017-05-11 5 by (mod) - plumber bleached our well due to a bad taste in the water, now we can't get rid of the bleach smell

Warren:

You may need to drain your water pressure tank and water heater (don't turn the heater back on until it's full of water or it may be destroyed or even dangerous), then flush the plumbing system.

But, if the plumber (stupidly in my OPINION) dropped solid chlorine tablets or pool tablets into the well it's much more difficult to flush the well until those are fully dissolved. So find out what she did.

On 2017-05-11 by Warren

A plumber bleached our well due to a bad taste in the water. Since then there is a bad bleach smell and taste and a soapy foam in the water.

We have run the water for hours to clear out the bleach smell and taste, both inside the house, the cold and hot water, and outside the house through a hose.

Nothing helps. As a matter of fact, it seems to be worse after running the water. What should we do to correct the problem?

On 2017-04-28 by (mod) - cause of yellowing of white clothes and tubs

Did you check the iron level of the water?

On 2017-04-27 by SUE

Thanks!
Don't have an odor or taste problem, just yellowing of white clothes and tubs. There wasn't a problem when I had a jet pump,

but when the submersible was installed, it seemed to pull up a lot more TDS. I have only had to disinfect twice, once after incompetent plumbers installed said pump, then again, as incompetent ME had not read this website, and was too timid to add enough bleach!

My set up is: Pump, pressure tank, sediment filter, acid neutralizer then softener. So far, so good. I am waiting for the ambient air in my house to warm up a bit before I do a bacteria screening, which I perform every year.

On 2017-04-27 by (mod) - are my sediment filters interfering with the chlorine?

Sue

Sediment filters should not affect dissolved disinfectant such as chlorine, but the order of placement of water treatment equipment is important.

Typically installers use first a sediment filter then an activated charcoal filter. Reducing sediment makes disinfection, such as by a UV light (downstream) more effective and more durable. Charcoal filters will remove odors and tastes including of chlorine disinfectant. They can also breed bacteria if kept too long in the system without changing.

If your filters clog quickly and are in the proper sequence, then you probably want to install a larger, higher capacity filtering system than you're presently using.

See details at WATER FILTERS, HOME USE

Also see CHLORINATORS & CHARCOAL FILTERS

On 2017-04-27 by Sue

I have very heavy iron and clay sediment, which I use a filter to remove post pressure tank.

When I have chlorinated my well in the past, I have put a fresh 10 micron filter in during the recycling process. The logic is to keep as much sediment out of my pipes and water heater tank, as the water gets stirred up and becomes quite muddy.

The first time I did this, I actually had to stop the process and change the filter, as it became so clogged no water would come from the hose bib.
The filters are simply poly and string-wound types; am I reducing chlorine by doing this?

My well is 70 foot, and chlorine seems to disclose itself fairly quickly. I also run off the pressure tank after everything is back to normal, until it runs clear again.
What are your thoughts on this? Am I doing this right, or wasting a filter or two?

On 2017-01-18 by (mod) - Typical fee for paying a water treatment or well company to sanitize your well

Handy and John:

Typical fee for paying a water treatment or well company to sanitize your well is $80. to $200. U.S.D. - depending on where you live, well depth, ease of access, and other variables.

On 2017-01-17 by johnthorson13@gmail.com

What would it cost me to have a Well Company chlorinate my well?

On 2017-01-17 by handyjack

to have a well co.clorinat my well should cost me how much? ??

On 2017-01-17 by handyjack

handyjack, to have a well co. clorinate my well should cost me how much? What should I charge to clorinat my customers well so she can pass inspection?

On 2016-10-21 7 by (mod) - how long does well decontamination last?

Seriously: it depends - on the source of contaminants. For example: a single event such as changing out a well piping: the shock treatment may be reliable for a year or longer. But if there is a persistent contaminant source such as surface runoff leaking into a well, then the well contamination will reappear in days.

Glibly: Until your truck reaches the end of the driveway;

On 2016-10-19 by Jeff G

Once I've completed the decontaminating procedure with bleach and it was successful, how long is the treatment good for? 6 months? year?
Thanks.

On 2016-10-18 by Christina

We shocked our well, 2 gal of bleach for approximately 300 gallons of water. I think we may have over chlorinated.

I borrowed a high end Chlorimeter from work to test my water. The levels go down and have been as low as 0.30 ppm but then go back up sometimes over 2ppm after my outside hose has been off a while.

Why does the chlorine keep coming back like that? I have my hose stretched out all the back in the woods away from the well casing,

I thought maybe it was just running back into the well. It's been 2 weeks now of running a hose outside almost 24/7. When is the chlorine going to go away?

On 2016-08-19 by (mod) - having trouble flushing out well after decontamination

Curious, Katie. Perhaps so much water was run out to flush the well and piping that you're pumping silt. But 10 days later I'd hope the silt would have settled out.

That leaves us thinking, as do you, iron. Have you tested tis brown water?

On 2016-08-18 by Katie

We had our well shocked approximately three weeks ago.

The testing strips confirmed no more chlorine roughly 8-10 days later but our water still has a brownish orange tint to it, which it did not have prior to shocking. Can it take more than three weeks for iron discoloration to resolve or does this indicate some other issue?

On 2016-08-06 by (mod) after chlorination our water is fizzy

I'm not sure what is the cause nor cure of the problem you describe; I'd first flush the system thoroughly, second be sure that the water softener or other treatment is in bypass as that will tell us if the problem is within a piece of equipment or in the water source.

On 2016-08-05 by Anonymous

after chlorination our water is fizzy and has a almost white film build up but no smell of bleach.

On 2016-04-08 by (mod) - shocked the well with a gallon of Clorox bleach - doesn't seem to have worked

Anon:

Shocking a well with one gallon of bleach is rather undetermined in its effect. To be effective you need the proper concentration of disinfectant in the well. When that is reached you can flush out the well and all piping 24 hours later. But you need to know how much water you're treating and put in the proper quantity of bleach.

If you used liquid bleach and are having trouble getting it flushed out it may help to drain your water tank and hot water tank.

On 2016-04-08 by Anonymous

It's been over a week Shocked well with 1 gallon Clorox bleach . Waited 3 hours ran water and outside spigots for almost an hour but never smelled the bleach. Now a week later there is still bleach smell in our water. How do I get the bleach out if my well water. It's been over screen and I can still smell it.

Question/complaint: My well ran out of water during the well-shock and flush-out procedure

you need to WARN people = re water discharge/well shocking. i ran my well out of water and made the situation WORSE.

Tell people not to run the water outside only for a half hour or so at a time!!!! NOT until Chlorox smell is gone - can take forever o get rid of Chlorox smell.... well needs to recharge. Now, listening to you folks, I have an even BIGGER problem. - M.P.

Reply:

Thank you for sending an important note of concern. We're on it.

Please see the warnings and procedures at WELL CHLORINATION & DISINFECTION and please let me know if any of that seems unclear or is missing anything.

Question: how do I get rid of chlorine in well water after shocking the well?

We shocked the well, it was 425 ft deep so we used 1 1/2 gal of bleach, it did not smell right away like it said. ran water in house for about 20 min and nothing, let set over night and then ran hose to recycle water. then we started smelling so we let it set again.

When flushing out we ran directly from where water enters home to outside plus rand faucets to clear out. Still strong chlorine, when I test it is orange when chlorine tester only has yellow.

We do get a lot of sediment from our well, ( brown Water) if used a lot. Any Idea how much longer it will be to clear out. Getting tired of having chlorine showers and smelling it all day long. - P.D., property manager, Harrisburg PA 8/27/2013

Reply:

IF (and this is not quite the case) your 425 ft. well were completely full of water and assuming it's a 6-inch casing, that's about 640 gallons of water in the well, plus additional water volume in the piping system.

According to CHLORINATION WELL SHOCKING PROCEDURE

1.5 gallons of household bleach was a stronger concentration than needed (1 gallon would treat about 500 ft. of water in a 6-inch well casing). Considering that if your well's total depth was just 425 ft. and that most likely the static head of water in that well was less than 425 feet total, the well was overdosed.

Overdosing with chlorine can indeed make for some extra trouble in flushing out the chlorine or bleach later.

Flushing out the well needs to run more than that volume, however, since you cannot by running water just draw out the static water that was treated with bleach; rather, water running into the well dilutes the bleached-water already therein;

You'll need to use water for several days to fully flush out the chlorine bleach; the exact volume and rate of flush-out also depends on the flow rate of the well.

Further, as you've run chlorinated water into a water pressure tank and water heater tank, those too need to be flushed, or simply drained and refilled - a step that can speed the flushout procedure. Try that and keep me posted.

Reader follow-up:

I believe [the chlorine concentration in our well water] is at 10ppm  

Reply:

The maximum residual disinfectant level goal (MRDLG) and also the maximum residual disinfectant level (MRDL) set by the U.S. EPA for chlorine in drinking water is

4.0 mg/L or 4 ppm or 4.0 mg/L or 4 ppm as an annual average respectively. [1]

I would - shut off water to the building, drain the water heater tank and pump pressure tank, run water outside - straight from the well via an outdoor faucet - and check the chlorine level there. That will help sort out chlorine remaining in the well water supply from chlorine that may have been left in water tanks and piping in the building.

If bleach was introduced into the well by pouring it directly into the well casing, it might help the flush-out procedure if you used a garden hose to recirculate some of the well water back to the well, using it to wash down the casing sides and center piping before continuing with the actual flush-out of the well itself.

Keep me posted; send along photos of your well equipment, tanks &c as that may permit further comment.

Citation on limits of chlorine in drinking water:

• [1] US EPA, "Water: Basic Information about Regulated Drinking Water Contaminants", retrieved 8/27/2013, original source http://water.epa.gov/drink/contaminants/basicinformation/disinfectants.cfm
• [1a] DRINKING WATER FROM HOUSEHOLD WELLS - PDF, U.S. EPA, Original source last retrieved 2/13/2013, original source: http://www.epa.gov/privatewells/pdfs/household_wells.pdf

Question: shocked the well, sat 13 hours, bad water pressure now

(May 14, 2011) Martin said:

We shocked our well today, we let it set for 13 hours plus when we turned the pump back on and started to flush the system out the water pressure dropped and is not coming back up and the water flow itself has slowed down alot. We turned the faucet and the pump back off. Now what do we do? Thanks for the help.

Reply:

I SPECULATE that your well shock procedure has disclosed a second, separate problem, loss of well prime due to a leak that you had not previously noticed. As long as the well pump was left with power on, a slow leak, such as in the well piping or at a check valve, would result in water pressure dropping until the pump turned back on. But with power to the pump turned off for 13 hours, the leak may have been enough to lose pump prime.

In such cases you can usually get water pressure back by re-priming the pump, but you'll need to find and fix the leak to avoid repeating this problem, to stop wasting water and electricity by unnecessary pump cycling, and to protect the pump and pressure control switch from early failure due to well pump short cycling.

Question:

(June 9, 2011) Becky said:

How long does it take for the chlorine to get out of the system?

We had our well pump replaced 2 days ago, there is a chemical smell and taste to the water, it is not getting any better over time.

Should I be concerned that the taste/smell are so strong so long after? How long should I wait to get the water tested?

Reply:

After 24 hours of disinfection you should be able to flush out the chlorinated water in less than an hour, unless there are unusual conditions in the well itself.

You'd have trouble flushing out the chlorine if

- some fool threw solid chlorine tablets into the well - they'll sit on the well bottom for quite some time

- there were large water tanks or water heater tanks that need to be drained

Watch out: Yes remaining bleach after well sterilization is a concern: too-high a concentration may be unsafe to drink (boiling the water may help drive off chlorine), and doing laundry with high-chlorine water may bleach clothing that you 'd prefer to have left alone.

Question: putting chorine in a well where I see electrical wires

(Aug 21, 2011) Pat said:

I see electric wires in my well....do I still put clorene in the casing and then flush with a hose to make sure the bleach is off the wires?

Reply:

Pat if you follow the chlorox bleach dilution recommendations and wash down the casing interior and wiring by recycling water from a hose bib back into the well you should be ok.

If you see open electrical splices stop and have those fixed first.

...

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-4 - more-recent questions and answers about solving problems when or after shocking a well

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

Suggested citation for this web page

WELL DISINFECTION FAQs-3 at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to WATER TREATMENT SYSTEMS

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