rehabilitation/
Field Diagnosis of Well and System Problems
Solving issues in the well is more important than ever before.
By David Hanson
T
he day is coming all too soon when drilling
new wells will become less of an option. It’s
critical to your survival to understand different directions that complement your business now.
Customers today are demanding more and better
answers, and it’s our job to understand and provide
solutions. Customers want more water and better
water. And when having problems, they want good,
solid answers.
This requires some education on our part. Part of
the problem is water chemistry; part may be biological (slime or odors), and part may be physical issues
with the well casing or piping. It will require some
work and it’s a little different than pulling levers
behind a rig, but this is an emerging market and you
need to be aware of it.
Some of the customers’ issues include coliform
bacteria, discolored water, odors, iron bacteria, corrosion. All are problems that can be understood and
solved. My intention here is to give you tips to use
in the field to understand what to look for and where
to look, and therefore give you a better chance to
solve your customers’ problems.
Odors in a New Well
Odors in potable water are most often caused by
bacteria, assuming there is no contamination present.
The most common complaint is the “rotten egg”
odor, normally caused by sulfate-reducing bacteria.
SRB are anaerobic only, which means they thrive in
low-oxygen or no-oxygen environments and require
some sulfate or gypsum as a nutrient.
They are naturally occurring soil organisms most
likely found in clay or shale lenses. These formations provide the low-oxygen environment and necessary nutrient. If screens are placed through clay
lenses or if an open hole is completed exposing open
shale lenses, this odor may be noticed immediately.
In the initial design, use shorter lengths of screen in
only clean sand/gravel areas. This will minimize or
eliminate the problem. If drilling in sandstone or
limestone formations, set and grout casing through
the deepest shale lenses and drill the clean part of
the formation, open hole.
If this problem already exists in a new well, do
not shock chlorinate as it will not solve the problem
more than short term. Plus, large amounts of chlorine causes corrosion to any metal in the well and
may even cause nonmetal parts like PVC to become
brittle.
When field testing a customer complaint:
● Check if odor is present in the hot water only
in the system. If in the hot water only, take the
anode rod out of the hot water heater.
● If odor is present in the cold water, pour a glass
of water. Let it set for 10 seconds. If the odor
goes away, it’s a gas probably caused by SRB.
If a bladder pressure tank was installed, the bladDavid T. Hanson, the 2003 NGWA McEllhiney Lecturer, is the
owner of Design Water Technologies, a company dedicated to
understanding and treating wells for iron bacteria and coliform.
You can contact him at designh2o@aol.com.
24/ April 2007 Water Well Journal
der contains this gas, so the first atmospheric
condition is at the faucet. Install a bladderless
tank, an open tank, or an air injection to an iron
filter. All allow oxygen contact to the water and
dissipates the odor. Over time there may be a
minor amount of sulfate powder that will accumulate in the bottom of the tank.
Odors Suddenly Appearing
in an Older Well
If this happens within a couple of weeks to years
of operation, you have to suspect that there may be
changes of environment in the well. A “rotten egg”
odor may be caused by SRB. Musty, oily, fishy, or
metallic odors can be caused by other slime formers
or iron bacteria.
Odors that suddenly appear when there is:
● Slime formation in the well can harbor anaerobic, odor bacteria beneath the polysaccharide
debris. Odors can vary in severity with time.
Check inside any piping for the presence of soft,
sludgy debris. For domestic systems, check at
the “union joint” by the pressure tank. For larger
systems, check a gasketed water meter or check
valve. You can also do “timed tests” to determine
the presence of hydrogen sulfide gas in the casing and aquifer.
● A sump in a well. A sump is a pipe below the
screen that allows sediment to collect, but is a
nonproductive zone that can harbor anaerobic
bacteria. This same condition can happen in the
bottom of a rock well in a nonproductive zone.
Look at the original drillers log for either condition. Either provides a low-oxygen environment
for anaerobic (odor). In some cases, you can
install an airline or water flushing tube into this
zone to automatically flush this area during
pumping.
● A simple change from a bladderless pressure
tank to a bladder tank in an older system.
A standard bladderless tank allows direct water to
air contact which releases the gas, and the odor is
dissipated within the tank. When a new bladder
tank is installed, the first atmospheric condition
occurs and the odor “suddenly” appears when it
was not present with the old tank.
● Potential for corrosion in the casing allowing
debris to fall into the well, creating potential
odors and discolored water on a continuous
basis.
Recommendations for Diagnosis
or Questions for Customers
Consider asking the following questions as well
as performing the following actions:
● Was a new bladder tank recently installed on a
domestic system?
● Look inside piping for the presence of slime
debris. Check union joints by the pressure tank
on domestic wells as well as gasketed water
meters, check valves, etc. on large diameter
wells.
●
●
Check the well log for the possibility of dead or
sump areas in the bottom of the well.
Test at the wellhead for presence and severity of
the odor in a timed test. Measure for hydrogen
sulfide gas on a timed test. For domestic wells,
test for hydrogen sulfide for one to two minutes
of pumping and at three hours of continuous
pumping. If hydrogen sulfide gas levels remain
the same or rise, the problem is in the aquifer.
If odor declines drastically, there may be a slime
growth in the well.
General Corrosion
Most ground water is not corrosive to a point of
major problems, but the majority of problems will be
caused by certain conditions. Some of these can be
caused by improper grounding.
Most water chemistry tests can be done by a
local lab or with a test kit. Check for:
● Total dissolved solids greater than 600 ppm
● Chloride greater than 500 ppm
● pH lower than 6.0
● Carbon dioxide greater than 50 ppm, but test
has to be done on-site
● Dissolved oxygen greater than 2 ppm, but test
has to be done on-site
● Hydrogen sulfide odor (rotten egg) caused by
sulfate-reducing bacteria
● Massive presence of any of the iron oxidizing
bacteria (iron bacteria).
Total dissolved solids greater than 600 ppm can
cause electrolysis between two different metals in
water that is highly conductive to energy. When any
dissimilar metals are placed in this type of water,
the lesser metal will show corrosion, and the nobler
metal may show deposits. The higher the TDS, the
greater the potential for issues.
Some examples of lesser metals are cast iron and
mild steel. Examples of more noble metals are stainless steel and hardened metals.
You may even see problems within the same
material, as simple differences can occur in the
metal itself. The rolling of metals, forming/shaping,
or the cutting of threads change the structure of the
metal. You will often find debris on the inside of
piping. For domestic systems, look inside the union
joint at the pressure tank. In large diameter systems,
look under a gasketed water meter or check valve
for debris. Scrape some debris and dry. Crush debris
into small particles and put on a piece of paper. Run a
magnet under the paper to understand the percentage
of particles that are magnetic. Magnetic debris is most
often a corrosion byproduct. Most mineral deposits
(iron, manganese) are not magnetic. A small percentage of dried bacterial deposits can be magnetic.
Recommendations for Normal
Corrosion Conditions
This is a condition that cannot be changed by
treatment. Simply move the corrosion issue to a
field diagnosis/continues on page 26
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field diagnosis/from page 24
replaceable metal at the well. This will require a
lesser noble metal, say magnesium.
This can simply be done by:
1. Strapping a magnesium wire to the pump column
pipe.
2. Burying a magnesium rod as a sacrificial anode
by the metal well casing. Dig a 3 to 4-foot-deep
trench near the well and place this rod horizontally. Attach one end of this rod with a cable
attached to the casing. You might be able to
increase conductivity by adding 3 to 4 inches
of bentonite chips below and above this rod.
Then simply check every three to four years and
replace when necessary. Call an oil pipeline or a
buried tank company to buy these magnesium
anodes.
Massive or Early Corrosion
Severe corrosion within a short period of time
(less than three years) may be resulting in more than
simple chemistry. Just one millivolt of stray DC voltage can dissolve 12 pounds of steel per year. If you
have reviewed the water chemistry and don’t find any
issues, try looking at stray DC voltage. This may take
the form of replacement pumps or drop pipe in a very
short period of time. If you see severe or early signs
of corrosion in a well or piping, check any hard
wiring in the area for stray DC voltage. This is done
with a “C” clamp-type DC voltmeter.
Sources of DC voltage may be phone lines, some
low voltage lighting systems, electric fences, and
corrosion protection of buried tanks or pipelines.
Stray DC voltage can even happen through ground
surfaces. Voltage will follow water that is highly
conductive. Clay lenses or shallow ground water
containing high TDS water may allow conductance
from miles away. You can use ground stakes in a circle around the well and measure resistance between
the stakes. If the source is within a household or
building through wiring, the ground must be
changed. See an electrician for this.
Coliform
There are potential problems with samples that
show multiple samples with “present” for coliform.
Some of the issues include:
Where the sample was taken. If you are taking a
sample at a house or somewhere in the system,
you must assume the problem can be from that
point backward to the well. Do not assume the
well is always the problem unless you are testing
at the wellhead. If problems persist, test at the
wellhead. Install a sample tap in the basement of
a new house to separate the well system from the
house piping.
Shelf life of liquid chlorine. Liquid chlorine (common bleach or industrial sodium hypochloride)
will lose up to 20% effectiveness every month.
Natural pH of water. If standard chlorine is used,
pH will rise as all liquid and granular chlorine is
an alkaline which causes a rise of pH. The more
chlorine you use, the higher the pH, and therefore the less effective it becomes. If natural pH is
7.0 or greater, consider using ChloraPal or similar chemistry to control pH with chlorine at
between 5.5 and 6.0 to make the chlorine 200
times more effective.
Placement of chlorine. Chlorine will not automatically mix evenly to the bottom of the well if
you pour it into the well from the surface. What
really happens is chlorine hits the static level,
causing a tremendously high pH (ineffective but
26/ April 2007 Water Well Journal
minutes. Minor MPN is less than 10 colonies/
100 mL. Major MPN is greater than 20 colonies/
100 mL.
● IF MPN is high in the “casing” sample and
low or zero in the “aquifer” sample, the
problem is probably contained in the well
and should be treatable.
● IF MPN is high in the “casing” sample and
high in the “aquifer” sample, consider a
continuing source of organisms, such as
failed grout allowing a continuous source
outside the casing from an upper level
source, a failure in the casing allowing a
continuing source inside the casing, a
source in the aquifer itself. You cannot get
a safe sample in this case until the physical
problem is fixed.
If you are testing in the system and continue
to get “presence” of coliform even with the
timed test, install a pressure gauge on the well
side of the pressure tank.
Allow the pump to build to shutoff pressure
(50 psi) and monitor pressure. If there is a leak,
the pressure will drop drastically within a few
seconds. Then you must lift the pump discharge
to make sure the check valve in the submersible
pump is holding. If the check valve is holding,
the leak is in the buried line and needs to be
replaced.
Just one millivolt of stray
DC voltage can dissolve
12 pounds of steel per year.
If you have reviewed the water
chemistry and don’t find any
issues, try looking at stray
DC voltage. This may take the
form of replacement pumps
or drop pipe in a very short
period of time. If you see
severe or early signs of
corrosion in a well or piping,
check any hard wiring in the
area for stray DC voltage.
highly corrosive), and very slowly sinks to lower
levels, but will not seek out bacteria. Pellets
placed in the well will sink to the bottom, but
will lie there undissolved for years. Consider
using two volumes of the well in a tank at the
well. Mix the desired chlorine into this tank and
pour or pump into the well. You will first displace the volume of water in the well, and the
second volume will flow into the formation.
Surge the well with either pressure from the surface or movement of the pump up and down to
create some movement for additional contact.
Presence of bentonite hiding coliform. If no or
little development was done in the well and
bentonite was used in the drilling process, the
blockage must be removed. To break bentonite:
(1) calculate the volume of the screen in gallons;
(2) multiply that volume by five; (3) have a tank
at the surface with that volume of water; and
(4) mix 0.03 gallon of common bleach per gallon
of water in that tank. This will create a pH of 10
and the oxidation process will break the polymer
chain of the bentonite. Place this equally throughout the screen with a tremie pipe. Surge the well
screen with a surge block. Let it set overnight.
Airlift the well from the bottom of the well for
removal. Dechlorination may be required.
Severity of problem, not just present/absent. If
you have had more than two “present” samples,
then ask your lab to do a “counts as MPN (most
probable number) of coliform.”
Understanding the location of coliform. If you
want to separate a well problem from a potential
aquifer problem, do timed testing. Here is the
procedure: Let the well set overnight with no
pumping. Sample at the wellhead for a “casing”
sample if possible. Let the pump run for 50 times
the volume of the well for an “aquifer” sample.
In domestic wells, take a “casing” sample at
one minute to two minutes of pumping and the
“aquifer” sample in three hours.
In large diameter wells, take the “casing”
sample at two minutes after water vacates the
pump and calculate the volume of the well and
divide by gallons per minute for sample time in
E. coli or Fecal Coliform
If E. coli or fecal coliform bacteria are present in
the sample, it means there is probably a physical
source causing the problem, which can be dead animals, fecal material, or sewage contamination. Do
not chlorinate the well, as chlorine will not remove
the physical source or fix problems with failed grout
or physical problems with the well.
If E. coli was present in a system, test at the
wellhead first. If present at the well, set an airline
to the bottom of the well. Airlift all debris out of the
well until the water is clear.
Chlorinate and retest. If you are still getting
“present” for E. coli, consider doing a timed test,
following the procedure that was explained earlier.
If there is a “present” in both the “casing” and
“aquifer” samples, consider the potential for a physical problem with the well casing (failed grout,
improper seating of the casing to rock, failed fittings
in casing). Understand the source before treating the
well. If negative at the well but positive somewhere
in the system, there is a problem in the system.
Plugging in line filters or pipelines, sudden
discoloration, sudden odors, or debris present on
pumps during routine maintenance. First, any
plugging or sudden discoloration, especially on
startup of the pump, may be caused by a mineral
buildup, slime created by bacterial activity, or
silts/fine sand. First, inspect piping. For domestic
systems, look into piping at the union joint by the
pressure tank for debris. For large diameter wells,
take off the covers on gasketed water meters or
check valves and inspect any residue on the inside.
This diagnosis is critical, as successful treatment is
based upon the problem.
Mineral Deposits
●
●
Debris inside piping is hard and will be scrapable in chunks or plates.
Coloration may be red/brown (iron), black and
brittle (manganese), light tan/brown (calcium),
or green (sulfate).
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field diagnosis/from page 26
●
●
Video of well will show flakes that will float
but sink to the bottom with camera movement.
Debris will be more noticeable in the screen area
or open hole only.
Check water chemistry, pH > 7.0, iron > 1.0
ppm, manganese > .02 ppm, sulfates > 40 ppm,
hardness > 200 ppm. Water chemistry should be
consistent over long periods of time. Compare
iron and manganese with past samples. If there
are major increases, see as follows.
Iron Bacteria, Slime Bacteria
●
●
●
●
●
●
●
●
Debris may be slimy, soft, granular sludgy.
Dried debris may be dusty or break apart easily
because of high oxygen content.
Color of debris may be brown, red, black, green,
or in some cases, clear.
Odors may be noticeable within debris.
Sudden odors may appear in the system and may
be rotten egg, fishy, oily, metallic, or musty.
Notice increasing or fluctuating levels of iron or
manganese.
Change in chlorine or phosphate injection rates
in a system.
Video may show stringy debris, fluffy debris, or
gelatinous masses. Puffiness may occur with
camera movement. Debris loosened will most
often float during camera movement. Debris will
be very noticeable from static to pumping level
and throughout the screen.
28/ April 2007 Water Well Journal
Low or Changing Yields
Finale
Customers may complain of air in the system
when plugging occurs in wells. A plugging of the
screen or fractures in an open rock well will not
allow normal flow of water to the well.
This will require more drawdown to attempt to
pump water. It is critical to understand the specific
capacity (SC) of the present well condition and compare to the original SC. If the original SC was 8
gpm/ft of drawdown and it’s now 3 gpm/ft of drawdown, the yield has declined 62% and needs some
attention. In some cases, the SC is never calculated
originally when the well was drilled. You have to
pump the well, so why not record the static level,
pumping level at a given time (say, 30 or 60 minutes
in domestic wells and three hours in a large diameter
well). You don’t even have to make the calculation
when the well is drilled; it can be done at any time.
It doesn’t take any more time but does require a
drawdown gauge.
A reduction of yield will be caused by either:
● Mineral deposits
● Slime or iron bacterial deposits
● Fine sand filling in a screen or caving formation
into an open borehole
● Changes in the static level in a water table aquifer drastically reducing the pumping capability
of the aquifer
● Changes in flow conditions within an aquifer due
to other wells in the area conflicting with flow or
even seismic changes restricting flows to a well.
That’s it. If you are stumped, seek out a lab service. It is critical to be correct on the diagnosis to be
successful.
When it comes to well rehabilitation, you have to
be a doctor of sorts to diagnose and solve the problem. The problem may be due to water chemistry,
microbiology, or physical issues with either the well
or the system. These physical issues can include
failed grouts allowing a continuing issue outside the
casing into the intake area of the well, failed well
casing allowing a continuing issue inside the casing
into the intake of the pump, or failed buried piping
where the problem occurs in the system but not the
well.
If you are looking for something more exciting
in your career, look at water treatment and well rehabilitation. The problem? Misdiagnosis will result in
failure. For example, if your customer has a slimy
growth in their system and you shock chlorinate the
well, you know it’s only a short-term fix. The problem will come back, but in a shorter frequency.
Do you treat again or solve the problem?
Mistreatment will result in continued problems.
But you can make more money if you solve problems. There isn’t much competition for someone
who solves the problem.
Why is this an emerging market? Regulations
will make it difficult to continue to drill wells.
Customers demand more water and better water
quality. Will you look at new directions? Are you
up to the challenge? Will you stand apart from the
crowd? I hope so. WWJ
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