I covered the basics of setting up equipment and preparing for
acidizing domestic water wells and installation of the acid in my last
column. If you missed it, it may be beneficial for you to review the previous column before reading this one.
I will now cover the monitoring of the acid after installation, well
development, and other considerations when acid is used in well
Prior to installation of the acid into the well and during the setup
phase for acidizing, I recommend a hose be connected to the discharge
port on the side of the casing. The hose should be of sufficient length
(usually at least 20 feet) to get the hose away from the well casing a
good distance. The purpose of the hose is to allow pressure to be bled
off should the pressure rise significantly.
While the acid is working in the well, you need to monitor the
pressure developing in the well. We typically relieve the pressure if it
rises to 100 psi or higher. When this pressure is relieved, you may get
either a water discharge or gas discharge from the acid reaction, or
Of course, safety is always a priority so the hose should be downwind
of where everyone is working and should be tied down and tethered to
prevent it whipping around when the pressure is released. Everyone
should be wearing protective gear as well.
We typically monitor the pressure gauge for up to two hours after the
acidizing if it appears there is a large pressure increase. Otherwise,
if no pressure is indicated on the gauge after an hour, we will often
leave the site. The minimum time to leave the acid in the well, in our
opinion, is four hours—and often if we acidize late in the day, we will
leave it in overnight.
When it’s time to open the well back up, we cut off the wellhead cap
and take it back to our shop for cleaning so we can reuse the cap on
We then remove the 1-inch conductor pipe from the well. Wear rubber
gloves compatible with acid during this process. When the conductor pipe
is removed, we wash it down with water on site to remove any residual
acid that may be on the pipe. This pipe, by the way, will start to rust
We then install our drill rods back into the well and prepare for
airlifting the well to develop the well and remove the fines and
residual acid. Typically, we start by installing the rods to 20 feet
below the static and start to airlift slowly.
If in an area where there is no natural water (river, creek, stream,
storm sewer) slowly discharge the water and monitor the pH of the water
as it leaves the casing. It is not uncommon to see the pH start at 4 or
5, but typically it will rise fairly quickly. We sprinkle soda ash in
the water as it exits the top of the wellhead and monitor the pH
downstream to ensure it is in the 6.5 to 7 pH range.
If you are in an area where there is natural water in some form, you
need to make provisions to ensure the discharge water is well treated
and has a neutral pH before it is left to run off. Be sure to check your
local regulations regarding this issue.
As the pH starts to get back to normal and the water starts to clear,
we slowly lower the rods farther into the well until we have bottomed
out. Understand since acid is heavier than water, it may have a tendency
to go to the bottom of the well, so be sure to continue monitoring the
pH the entire time you are discharging. Once you are on the bottom, the
pH is back to normal, and the fines are diminishing, you can check the
pH less often.
When the well has reasonably cleared, I suggest surging the well a
couple times and seeing how the turbidity is, and the pH. Sometimes you
will see a spike in the pH or a surge of fines when surging the well.
The well should be surged until the pH does not fluctuate when surging.
Some other things to keep in mind:
In summary, we have found acidizing water wells to be a great aid to
us and our customers. As with any process, experience helps — but you only
get experience by doing it. Over all the years I was in the business,
the acidizing process we started with and evolved to has changed
dramatically, and will continue to evolve as we continue to learn.
Gary Shawver, MGWC, is president of
Shawver Well Co. Inc., an employee stock ownership plan company in
Fredericksburg, Iowa. He has been in the water well industry for 40
years and is a Master Groundwater Contractor. He has served as president
of the Iowa Water Well Association, the Iowa Groundwater Association,
and most recently served on the NGWA Board of Directors. Shawver is
semiretired, having sold his business to his employees. He can be
reached at email@example.com.
The views expressed in this column are the author’s opinions based on his professional experience.
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