What is down the hole construction drilling? A complete guide
Down The Hole (DTH) drilling is a key technique in modern construction drilling, mining, and water well projects. Known for its efficiency in hard rock formations, DTH drilling allows contractors and engineers to drill deeper, faster, and with greater precision than many traditional methods. At Wassara, we specialise in water-powered DTH drills that offer safe, cost-effective solutions for construction drilling in demanding environments. This guide explains what DTH drilling is, how it works, and why it’s an essential method in today’s industry.
1. What is down the hole drilling?
Down the hole drilling is a type of percussive drilling where a hammer is located directly behind the drill bit, inside the borehole. Unlike top hammer drilling, where impact energy is transmitted down the drill rods, DTH drilling delivers the hammer’s impact directly at the rock face.
This approach makes DTH drilling highly effective for deep boreholes, hard rock formations, and construction drilling projects where precision and speed are essential. Common applications include drilling foundations, shafts, tunnels, and water wells.
2. How DTH drilling works
DTH drilling uses a hammer that repeatedly strikes the rock at the bottom of the hole while rotating the drill string. The hammer can be powered by either compressed air or water:
- Air-powered DTH hammers: Compressed air drives the hammer, removing cuttings from the hole and allowing fast penetration in most rock types.
- Water-powered DTH hammers: Water-powered drills use high-pressure water to drive the hammer, reducing dust, vibration, and noise. This makes them ideal for construction drilling in urban areas or environmentally sensitive sites.
The choice between air and water power depends on site conditions, environmental regulations, and project goals. Regardless of the method, DTH drilling allows contractors to maintain high accuracy while drilling deep, straight holes.
3. Benefits of DTH drilling in construction projects
Precise and straight holes – DTH drilling ensures vertical and straight boreholes, which is critical for construction drilling where foundation alignment and structural accuracy matter. The hammer directly impacts the rock, preventing deviation often seen with top hammer methods.
High penetration rate – By delivering energy directly to the drill bit, DTH hammers penetrate hard rock faster than many conventional drills. Faster drilling translates into reduced project timelines and lower operational costs.
Versatility across applications – DTH drilling is used in a wide range of construction drilling projects: foundations, tunnel shafts, pile drilling, geothermal wells, and water wells. Its ability to handle both soft and hard rock makes it a flexible choice for contractors.
Safer and environmentally responsible – Water-powered DTH drills reduce airborne dust, vibration, and noise, improving safety on site and lowering environmental impact. Compared with explosives or top hammer drills, DTH drilling is a controlled, cleaner alternative for urban construction projects.
4. Key components of a DTH drill
Understanding the components helps explain why DTH drilling is so effective in construction projects:
- Drill bit: The cutting tool that penetrates rock. Available in various types for different rock hardness and applications.
- Hammer: Positioned behind the bit, delivers rapid impacts to fracture rock.
- Drill rods: Connect the hammer to the rig at the surface, transmitting rotation and feed force.
- Power source: Air or water provides the energy for hammer operation and removal of cuttings.
Each component is engineered to optimise efficiency, reduce wear, and maintain straight boreholes, ensuring predictable results for construction drilling projects.
5. Choosing the right DTH drill for construction drilling
When selecting a DTH drill for construction projects, consider:
- Rock type and hardness – harder rock requires a more robust hammer and drill bit design.
- Depth of hole – deeper holes benefit from DTH hammers, which maintain straight trajectories.
- Environmental factors – urban sites may prefer water-powered DTH for reduced dust and noise.
- Project scale – larger construction projects may require rigs with higher feed pressure and torque for efficiency.
Working with experienced suppliers like Wassara ensures your DTH drill is matched to project needs, maximising performance and minimising downtime.
A drilling method that delivers results
Down the Hole drilling has become a cornerstone of modern construction drilling because of its precision, speed, and versatility. Whether used for foundation work, tunnelling, or water wells, DTH drilling delivers straight, clean, and accurate boreholes, while water-powered solutions further improve safety and environmental performance.
At Wassara, our water-powered DTH drills are engineered to optimise construction drilling in the toughest conditions, helping contractors reduce costs, improve accuracy, and meet project timelines.
To learn more about DTH drilling and how our water-powered solutions can support your next construction project, visit ‘Our products‘ page or contact a Wassara representative. You can also follow us on LinkedIn for the latest case studies, technical insights, and updates on our construction drilling innovations.
