Most owners collect two or three drilling quotes, see numbers that sit far apart, and assume someone is overcharging. Usually nobody is. The quotes are describing different amounts of work, and the smallest number is very often the one that stops earliest: it prices a hole in the ground, while the thing you actually need is water arriving at a tap.
This article is about reading the paperwork, not about what drilling costs. The factors behind the price itself, depth, geology, access, casing, are covered separately.
Drilling cost and system cost are two different numbers
A borehole on its own does nothing. Before the water reaches the house it needs casing and a developed, clean bore, a pump matched to the well, cable and a control box, usually a storage tank, often treatment, and the trench and pipework that connect all of it. On a typical villa project the drilling itself is only one part of the final budget, and treating a drilling-only price as the cost of having water is how projects end up stalled halfway.
Neither number is more honest than the other. A drilling-only quote is fine when you already have a contractor handling the rest. The problem is comparing a drilling-only offer against a complete-system offer as if they were the same product.
What a complete quotation itemizes
- The pricing basis for depth: what is included, and what happens per metre beyond it
- Casing material, diameter and depth, and where the screen sections go
- Well development and cleanup after drilling, and a yield test with written results
- The dry-hole policy: what you pay if the bore finds too little water to use
- Pump make and duty point, installation depth, cable, and the control and protection gear
- Storage tank size and stand, if included, and the connection to the house
- Trenching, pipework and electrical work, and who supplies power to the pump
- What is excluded, in writing, so the gaps are visible before work starts
A quote does not have to include everything to be a good quote. It has to say clearly which of these lines it covers. The offers that cause trouble are the ones that leave the list unstated and let the owner discover the missing lines one invoice at a time.
Why two quotes for neighbouring plots differ
Even for the same scope, two honest quotes can land apart. Contractors carry different assumptions about depth on your particular hillside, different casing standards, different rigs with different access needs, and different appetite for the risk that the first bore disappoints. A quote that assumes ninety metres and one that assumes fifty are not disagreeing about margin, they are disagreeing about your geology, and the site visit is what settles that argument.
Putting offers side by side
The workable method is to rebuild every offer to the same scope before looking at the totals. Take the widest quote as the checklist, then price the missing lines onto the narrower ones, asking each contractor to fill their own gaps rather than guessing. Quotes compared this way often reverse their order: the cheap one grows, the expensive one turns out to have been complete all along.
Watch the per-metre structure especially. A low headline number with an open-ended per-metre rate beyond a shallow assumed depth transfers all of the geological risk to you. A higher fixed number that carries a realistic depth assumption is frequently the cheaper contract by the time the well is real.
What we quote
Deep Well Samui surveys the site first, free, and then issues a fixed written quotation with the casing spec, depth basis, dry-hole terms and any system components itemized. The finished wells behind that process are on the projects page. If you are holding quotes that refuse to line up, send them over with your location and we will tell you plainly what each one covers.