CT Well Driller common mistakes
CT Well Driller · Understand the traps and how to avoid them.
Mixing up grout volume calculations by using the borehole diameter instead of the annular space between the borehole wall and the casing, leading to overestimating or underestimating the required grout quantity.
Candidates often memorize a single formula (e.g., volume = π × r² × depth) and forget that grout fills only the annulus, not the entire borehole. They may also overlook that the casing occupies volume, so the correct formula is π × (R_borehole² - r_casing²) × depth.
What to do instead
Always compute annular volume: V = π × (R² - r²) × h, where R is borehole radius and r is casing outer radius. Practice with realistic numbers: a 6-inch borehole with 4-inch OD casing gives an annulus area of π × (3² - 2²) = 5π ≈ 15.7 in². Convert units consistently (e.g., to gallons: 1 gallon = 231 in³).
Misapplying Connecticut setback distances for wells relative to septic systems, property lines, and other features, such as using the state minimum for septic tanks (25 ft) when the required distance to the actual leaching field is greater (75 ft).
Candidates memorize a single number (e.g., '50 feet from septic') without distinguishing between tanks, distribution boxes, and leaching fields. They also confuse recommended distances from other states or older codes with current Connecticut Public Health Code requirements.
What to do instead
Create a table of Connecticut setback requirements from the PHC (Section 19-13-B51) and RCSA 25-128-1 et seq., noting separate distances for septic tanks (25 ft), leaching fields (75 ft), property lines (10 ft), and surface water (25 ft). Verify the latest amendments and practice applying them to site plan scenarios.
Confusing the definitions and required actions for a 'well' versus a 'geothermal borehole' under Connecticut regulations, such as failing to recognize that geothermal boreholes must be grouted but do not require a pump test.
Candidates lump all drilled holes into the 'water well' category and overlook the separate provisions for geothermal systems in RCSA 25-128-1 et seq. They may also miss that geothermal boreholes require a different permit and grouting standard.
What to do instead
Study the definitions in RCSA 25-128-1: 'well' means a hole drilled for the purpose of obtaining groundwater; 'geothermal borehole' is defined separately. Note that geothermal boreholes require grouting to protect groundwater but do not require yield testing. Review the permit application forms for each type.
Assuming that a well's yield is equal to the pump's discharge rate during a pump test, instead of measuring the stabilized drawdown and specific capacity.
Candidates observe a pump producing 10 gpm and conclude the well 'yields 10 gpm', ignoring that the well may be capable of more or less depending on drawdown. They also forget that yield is determined by the safe yield at a specified drawdown, not by pump capacity.
What to do instead
Learn the step-drawdown test method: measure static water level, then pump at increasing rates and record stabilized drawdown. Calculate specific capacity (gpm per foot of drawdown) and use it to estimate yield at a permissible drawdown (e.g., to the top of the screen or pump intake). Practice with sample data.
Ignoring the requirement to maintain a minimum 50-foot distance between a new well and an existing well on the same or adjacent property, unless a variance is obtained.
Candidates focus on setbacks from septic systems and property lines but forget the well-to-well isolation distance. They may also think the distance is 25 feet or that it only applies to public water supply wells.
What to do instead
Memorize the Connecticut well isolation distance: 50 feet between a new well and any existing well, unless a variance is granted by the local director of health. Review RCSA 25-128-1 and PHC 19-13-B51 for exceptions. Practice site plans with multiple wells.
Selecting a pump based on horsepower alone without matching the pump curve to the well's yield and total dynamic head (TDH), resulting in a pump that either runs dry or cannot deliver the required flow.
Candidates often choose a pump by 'rule of thumb' (e.g., 1 HP for a 4-inch well) and neglect to calculate TDH, which includes static water level, drawdown, elevation difference, and friction losses. They also overlook the pump curve's efficiency range.
What to do instead
Practice calculating TDH: TDH = static water level + drawdown + elevation rise + friction loss. Then select a pump whose curve intersects the desired flow rate at that TDH, ideally near the best efficiency point. Use manufacturer pump curves and verify that the pump will not upthrust at low flow or run dry.
Failing to recognize that grout must be placed from the bottom up using a tremie pipe, and instead pouring grout from the surface, which can bridge and leave voids.
Candidates may have seen surface pouring on shallow wells or assume that gravity will carry the grout down. They underestimate the risk of voids and contamination when grout is not placed under pressure from the bottom.
What to do instead
Study the grouting procedure in AWWA A100 and Connecticut regulations: use a tremie pipe lowered to the bottom of the annular space, pump grout continuously until it returns at the surface, and verify the volume placed matches the calculated annular volume. Never drop grout from the top.
Misinterpreting drawdown as the difference between static water level and the pump intake, rather than the difference between static and pumping water levels.
Candidates confuse drawdown with the available water column above the pump. They may also forget that drawdown is measured in the well, not in the pump column.
What to do instead
Define drawdown clearly: drawdown = static water level (before pumping) minus pumping water level (during pumping). Practice with field data: if static level is 50 ft and pumping level is 70 ft, drawdown is 20 ft. Use this to calculate specific capacity and to set the pump depth safely below the pumping level.
Overlooking the requirement to disinfect a new well with a chlorine solution of at least 50 ppm and to allow a contact time of at least 2 hours (or 24 hours for high-turbidity water) before flushing and sampling.
Candidates may remember 'chlorinate the well' but forget the concentration and contact time, or they may use household bleach without calculating the dose. They also may sample too soon after disinfection, leading to false negative bacteria results.
What to do instead
Memorize the disinfection protocol: calculate the volume of water in the well and use the formula to achieve 50–100 ppm chlorine (e.g., 1 gallon of 5.25% bleach per 500 gallons of water gives ~100 ppm). Circulate, then let stand for at least 2 hours (24 hours if turbid), flush, and wait at least 7 days before sampling for bacteria.
Failing to properly abandon a well by not removing the casing to at least 5 feet below grade or not filling the entire well with approved grout, leaving a conduit for contamination.
Candidates may think that simply filling the well with sand or drill cuttings is sufficient, or they may leave the casing in place and cap it. They underestimate the risk of vertical migration of contaminants through an improperly abandoned well.
What to do instead
Follow Connecticut well abandonment requirements: remove the casing to at least 5 feet below grade, fill the entire well with approved grout (e.g., neat cement or bentonite), and cap the top. For artesian wells, use a grout plug at the top. Document the abandonment with a well abandonment report.