What the compressor does on a water-well rig
On a down-the-hole (DTH) rig, compressed air does three jobs at once. It drives the piston inside the hammer, which strikes the bit thousands of times a minute. It flushes the cuttings from the bit face and carries them up the annulus between drill pipe and hole wall. And once the hole meets water, it must lift that water column out as well. If any of the three falls short, drilling slows, bits wear, and the risk of a stuck string rises.
That is why the compressor is the heart of a borewell rig, and why a rig owner should treat its selection, maintenance and spares as seriously as the rig itself. For a step-by-step sizing method with worked figures, see our water-well compressor sizing guide.
Where the compressor sits: onboard, external or booster
Water-well rigs in India use several arrangements. Knowing which one you have is the first step in any enquiry.
| Arrangement | Description | What to confirm |
|---|---|---|
| Rig with onboard compressor | Compressor mounted on the rig truck, often driven by the truck engine or its own engine | Rated cfm and psig, airend and engine condition, drive arrangement |
| Rig with external compressor | Separate truck-mounted or trailer compressor connected by hose | Inlet connection, hose rating, distance, compressor capacity |
| Onboard plus auxiliary | Second compressor added for deeper or larger holes | How the two are connected, check valves, matched pressures |
| Booster-assisted | Booster raises pressure from a primary compressor for deep wet holes | Booster inlet and outlet ratings, staging and safety valves |
| Temporary replacement | Hired machine while the rig’s own compressor is repaired | Pressure, flow and connections that match the hammer and rig |
Typical pressure and flow bands
Pressure and flow depend on hole diameter, depth, water level and the hammer. The bands below reflect common practice for water-well and borewell work in Telangana, Andhra Pradesh and across India.
| Pressure band | Typical flow | Typical use |
|---|---|---|
| 200–250 psig (13.8–17.2 bar) | 600–900 cfm | Shallower holes, smaller diameters, firm dry formations |
| 250–300 psig (17.2–20.7 bar) | 800–1,200 cfm | Common borewell depths and diameters, moderate water |
| 300–400 psig (20.7–27.6 bar) | 1,000–1,500 cfm | Deep holes, high water inflow, larger hammers |
| Up to 35 bar (507.6 psig) | Special units | Very deep or very wet holes, booster duty |
Pressure must overcome hammer resistance plus the weight of any water standing in the hole; every 10 m of water above the hammer adds about 1 bar (14.5 psi). Flow must keep the uphole air velocity high enough to lift cuttings. A machine with plenty of pressure but too little flow drills slowly and leaves cuttings in the hole; plenty of flow at too little pressure stalls once water rises.
Types of water-well compressor
- Oil-injected rotary screw, single or two-stage: the most common modern choice, giving steady flow and pressure. Two-stage designs reach the higher pressure bands more efficiently.
- Truck-mounted or deck-mounted units: built onto the rig or a carrier truck; common on Indian rigs.
- Trailer or skid high-pressure portables: used as external or auxiliary air.
- Reciprocating high-pressure units: older or specialised designs, still found on some rigs.
- Boosters: reciprocating machines that raise the pressure of a primary compressor’s air.
What wears and fails, and why
Borewell compressors work in dust, heat and heavy load for long shifts, often far from a workshop. Most failures follow from a few predictable causes:
| Symptom | Likely causes | What we check |
|---|---|---|
| Low pressure or slow drilling | Worn airend, inlet valve fault, air filter blocked, engine down on power, leaks | Flow and pressure under load, inlet valve, filter restriction, engine speed |
| High discharge temperature shutdown | Dust-packed cooler, low oil, wrong oil, thermostatic valve fault, 40–45 °C ambient | Cooler cleanliness, oil level and grade, thermostat, fan drive |
| Oil carry-over into the air line | Separator element failed, scavenge line blocked, oil overfilled | Separator differential pressure, scavenge orifice, oil level |
| Engine stops on low oil pressure | Low engine oil, worn bearings, sensor fault | Oil level, actual pressure with a test gauge, sensor |
| Safety valve lifting | Regulator or controller fault, blocked downstream | Set-point, minimum-pressure valve, safety valve rating |
Normal oil-injected screw discharge temperature is about 75–95 °C. Dust is the biggest enemy on borewell sites: keep air filters, cooler fins and the engine radiator clean, and change elements to the dust load rather than strictly by hours.
Buying new, buying used or hiring
New machines suit rig owners starting a long-life fleet or moving to deeper, higher-pressure work. Used and refurbished machines lower the entry cost but need careful inspection of the airend, engine, separator tank and running hours. Hire suits seasonal peaks, government or project campaigns with a fixed term, and cover while your own compressor is under repair. Many rig owners combine all three: own the base fleet, hire for peaks and breakdowns.
When comparing machines, judge them on delivered flow at the pressure you actually drill at, fuel use under load, ease of service in the field and availability of spares, not on cfm alone.
For government water projects, irrigation schemes and real-estate or industrial borewells, the same rule applies: specify the deepest and wettest hole in the programme, and confirm the compressor can deliver its flow at that pressure in summer heat. A machine that only just copes in the cool months will struggle in May.
Running a borewell compressor well
- Warm up before loading and cool down before shutdown.
- Drain water from the separator and fuel water trap daily.
- Check oil levels, coolant and air filter indicators every shift.
- Blow out coolers and radiator regularly in dusty seasons.
- Inspect hoses, whip checks and couplings before every hole.
- Record running hours, pressures and discharge temperature; changes in these numbers warn of trouble early.
Hoses, connections and site safety
At 200–400 psig (13.8–27.6 bar), a borewell air line stores a great deal of energy. A burst hose or a coupling that parts under pressure can whip violently and injure anyone nearby. Use hoses and fittings rated above the compressor’s maximum pressure, fit whip checks or safety cables across every coupling, and replace hoses that show cuts, bulges or crushed sections. Never disconnect a line until it has been vented. Keep the compressor’s safety valve in good order and never adjust it to gain pressure. Standard safety shutdowns on these machines include high discharge temperature, low engine oil pressure and high coolant temperature; a repeated trip is a warning to investigate, not a nuisance to bypass. Park the compressor on firm, level ground with its cooling air inlet away from the dust plume from the hole, and keep the exhaust downwind of the crew. Refuel only with the engine stopped, and keep a fire extinguisher on the rig.
How Reddy Compressors helps
We supply all types, all brands and all models of borewell compressors: new sales, used and refurbished machines, rentals, service and spare parts. We work on ELGi, Atlas Copco, Ingersoll Rand, KAESER, Chicago Pneumatic, Doosan, Sullair, Kirloskar and other makes as an independent multi-brand specialist, not an authorised dealer. We have tie-ups with all major and reputed brands.
From our office at Tarnaka, Secunderabad, more than 20 service engineers and technicians cover the whole of Telangana and Andhra Pradesh, and we supply compressors, rentals and spares to rig owners across India. Our own fleet includes diesel portables and high-pressure units. Spare parts are identified from the nameplate, serial number and the old part, and fit is confirmed before we quote. We have also supplied high-pressure air on demanding project work, including a temporary package for a natural-gas development at Kakinada with compressors rated 1,100 cfm at 300 psig.
What to send us
- Rig make and model, and whether the compressor is onboard or external.
- Hole diameter, planned depth and expected water level.
- Hammer size and make.
- Required pressure and flow, if known.
- For service or spares: compressor make, model, serial and a nameplate photo.
- Whether you need to buy new, buy used, hire or repair.
Frequently asked questions
What size compressor do I need for borewell drilling?
Most water-well and borewell rigs use 600–1,500 cfm at 200–400 psig (13.8–27.6 bar). Shallower, smaller holes in dry ground sit at the lower end; deep holes with heavy water inflow need the higher bands, and special units reach 35 bar. The exact choice depends on hole diameter, depth, water level and hammer, so send us those details and we will match a machine.
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Why does my borewell compressor lose pressure when the hole hits water?
Water standing above the hammer adds back pressure, roughly 1 bar (14.5 psi) for every 10 m of water column. The compressor must also lift that water to the surface. If the machine is already near its limit, pressure at the hammer falls and drilling slows. A higher-pressure compressor, an auxiliary machine or a booster is the usual answer for deep wet holes.
Do you supply spare parts for all borewell compressor brands?
Yes. We supply spares for all types, brands and models of borewell compressors, including air and oil filters, separator elements, valves, sensors, airend bearings and seals, and engine parts. We identify each part from the make, model, serial number, nameplate photo or the old part, and confirm fit before quoting. Parts are supplied across India.
Can I hire a borewell compressor while mine is being repaired?
Yes, temporary hire while your own machine is under repair is a common request. We need the pressure and flow your hammer and hole require, and the connection arrangement on your rig, so the hired machine matches. Our fleet includes diesel portables and high-pressure units, and we serve rig owners across Telangana, Andhra Pradesh and beyond.
Is a used borewell compressor a good buy?
It can be, if inspected properly. Check running hours, airend noise and delivered flow under load, discharge temperature, engine smoke and blow-by, the separator tank and the controls. A refurbished machine with a documented service history is a safer purchase than an untested one. We sell used and refurbished borewell compressors and can inspect one you are considering.
How often should a borewell compressor be serviced?
Follow the maker’s intervals for compressor oil, filters, separator element and engine service, and shorten them for heavy dust. Daily checks of oil, coolant, filters and drains matter as much as the scheduled service. On our own hire jobs we change oil and service every 300 running hours, which is a sensible benchmark for hard field duty.
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Technical content reviewed by D. Srinivas Reddy, Managing Partner and service engineer, Reddy Compressors. Last updated 17 October 2026. How our engineering content is reviewed.