Common Drilling Problems (e.g., no water, low water yield): Causes and Preliminary Diagnosis

Common Drilling Problems (e.g., no water, low water yield): Causes and Preliminary Diagnosis

After drilling is completed, problems such as no water or a water yield far below expectations sometimes occur. Understanding the common causes of these problems and learning how to make a preliminary diagnosis will help you communicate effectively with the contractor or guide subsequent remedial measures. The root causes of the problems mainly stem from three aspects: underground geology, construction techniques, and well structure.

First, the most common and fundamental problem is "insufficient groundwater in the encountered strata." This is a geological reason, meaning that the area where the borehole is located has inherently limited groundwater resources, or the borehole did not reach the main aquifer (water-bearing layer). Preliminary diagnosis method: You can inquire about the water well conditions of your neighbors. If nearby wells are generally very deep or have low water yields, it is likely a regional problem. If the drilling records show that the entire process mainly involved dry, hard clay or intact rock, without encountering obvious permeable strata such as sand or gravel layers, this also points to this reason.

Secondly, improper construction techniques are a key human factor leading to insufficient water or water quality problems. There are two main situations:

Misalignment of the well screen with the aquifer: The perforated well screen (slotted pipe) was not aligned with the actual water-bearing sand or gravel layer, but rather with an impermeable clay layer. Water cannot easily enter the well.

Incomplete backfilling or well development: The gravel (filter material) filled outside the well casing is substandard or uneven, or the well development process was insufficient in terms of force and time, failing to effectively clear the aquifer channels. This results in water slowly seeping in, but the volume is very small, and the water may remain turbid and sandy for a long time.

Preliminary diagnosis method: For the first case, you need to check the "strata record" from the drilling process to see if the well screen position matches the aquifer depth. For the second case, if the well produces water but the volume is small, and the water continuously contains fine sand during pumping, it is likely that there is a problem with the filter material or well development.

Furthermore, well structure or later maintenance problems can also lead to a decrease in water yield.

Well casing blockage or rupture: The filter holes of the well casing are blocked due to chemical scaling, bacterial growth, or long-term intrusion of fine particles. Alternatively, the well casing may crack due to quality issues or external forces, leading to muddy water and allowing good water to leak into other undesirable layers.

Improper water pump selection or placement: The pump's pumping capacity is too large, exceeding the well's water output capacity, causing the water level to drop rapidly below the pump's intake, resulting in a "dry pumping" phenomenon, manifested as intermittent water flow or low water volume. If the pump's intake pipe is positioned too high, it won't be able to draw water from deeper levels.

Natural sedimentation: After long-term use, sediment will naturally accumulate at the bottom of the well, reducing the water storage space.

Preliminary diagnostic methods:

For blockage/cracking: If the well initially had sufficient water flow, but it gradually decreases over time, accompanied by changes in water quality (such as rust color or odor), it may be due to blockage. If muddy water suddenly appears and the water volume decreases sharply, it may be due to a cracked well casing.

For water pump problems: Observe the pumping situation. If the water flow is normal at first, but stops after a short period of pumping, and then resumes after a while, it is likely that the pump's pumping capacity is too high or the water level is dropping rapidly (the well's water output capacity is insufficient). Check if the pump is installed at a sufficient depth.

For sedimentation: Use a rope to suspend a weight and measure the current depth of the well, comparing it to the depth recorded when the well was drilled. If it is significantly shallower, it indicates sedimentation.

When encountering these problems, the first step is to gather as much information as possible (drilling records, initial water volume, surrounding conditions) and perform the above preliminary diagnosis. This will help you communicate more professionally and efficiently with the construction company or maintenance personnel. Most process or structural problems can be remedied through professional methods (such as realigning the filter pipe, high-pressure well cleaning, repairing the well casing, sludge removal, etc.). Problems caused by geological reasons may require deepening the well at the original location or drilling a new well at a different site.