The honest answer to 'what will a well cost?' is that it depends on your specific site — which is why we survey before we quote, not after. But the drivers are not a mystery. Four of them decide where your project lands, and understanding them tells you what the survey is actually measuring.
1. Depth to water
This is the single biggest cost driver, and it varies street to street on Samui. A coastal plot and a hillside plot ten minutes away can need very different depths. Deeper means more drilling time, more casing and a stronger pump later — so the survey's first job is an honest expected-depth range for your site, not a guess from the next road over.
2. Ground and rock conditions
Samui is a granite island under weathered rock and sediment. Soft ground drills quickly; hard granite layers drill slowly and sometimes need different tooling. Two sites at the same depth can differ in cost purely because of what the drill has to pass through.
3. Site access
The rig has to reach the drilling point. Narrow sois, steep hillside approaches and soft ground all affect which rig can get in and how long setup takes. Access is one of the things the survey checks on foot — it is far cheaper to find a problem before the rig is booked than on the day.
4. Casing specification
Casing is sized to your water demand and the ground it sits in, and it is not the place to cut corners — it is what decides whether a well lasts decades or silts up in a couple of years. A household well and a resort well are specified differently.
Common questions
Do deeper wells always cost more? Usually, because depth adds drilling time, casing and pump power — but a shallower well in hard rock or a tight-access site can cost as much as a deeper, easier one. Depth is the biggest factor, not the only one.
Is the survey really free, and is the quote fixed? Yes to both. The survey is free and takes about an hour; the written quote after it does not move once you agree it. Where a dry-hole risk exists, the policy for that is in the quote too, not improvised later. Indicative starting prices appear on the drilling service page as the business confirms them; until then, the survey is how you get a real number for your site.