Both will keep your irrigation system running. But borehole and mains water come with very different costs, responsibilities and lead times, and the wrong call either wastes money for years or leaves you short of supply at the worst possible moment.
Here’s how they actually compare.
How each one works
Mains water arrives already treated, pressurised and metered. You pay for what you use, there’s no licence to apply for, and it’s ready from the day the connection goes in.
Borehole water is your own supply, drawn from groundwater beneath your site. Once it’s drilled, tested and connected, the ongoing cost is little more than the electricity to pump it — but you carry the upfront investment, the testing, and — above the Environment Agency’s daily abstraction threshold — a licensing requirement.
Side by side
| Factor | Mains water | Borehole water |
|---|---|---|
| Upfront cost | Low — connection charge only | Higher — depends heavily on depth, geology and site access |
| Running cost | Ongoing, metered, scales with use | Minimal once installed, aside from pumping electricity |
| Licensing | None required | Abstraction licence needed above the Environment Agency’s daily threshold |
| Reliability | High, backed by the water company | Depends on aquifer yield — needs a survey to confirm |
| Water quality | Treated and tested by supplier | Needs its own testing before relying on it for irrigation |
| Pressure | Regulated, but not sized around your peak demand | Set by your own pump — sized to your system from the start |
| Best for | Lower or intermittent demand, fast setup | High, consistent demand where payback justifies the upfront cost |
Where mains water wins
For lower or seasonal demand, mains is hard to beat on simplicity. No survey, no licence application, no lead time — you connect and you’re running. If your peak-day usage sits comfortably below the abstraction-licensing threshold, the case for drilling a borehole instead of simply paying for mains gets harder to make.
It’s also the lower-risk option: there’s no aquifer yield to misjudge, and no dry summer where a borehole’s output drops off just when you need it most.
Where a borehole wins
For consistent, high-volume demand, the maths flips. The upfront cost of drilling varies widely with depth and local geology — no two sites are alike — but once the borehole is in, the water itself costs next to nothing. On a site drawing serious volume year-round, the mains bills saved can repay that investment; how quickly depends entirely on your demand and your ground, which is exactly what a survey establishes.
A borehole also gives you independence from hosepipe bans and supply restrictions that can hit mains customers in a drought — a real consideration if your business depends on watering happening every day, no exceptions.
If your demand is likely to cross the abstraction threshold, factor the licence application into your planning too. We cover the licence types and how the threshold is calculated in our guide to water sourcing for irrigation.
So which should you pick?
- Choose mains for lower or intermittent demand, or where speed and simplicity matter more than long-term running cost.
- Choose a borehole for high, consistent demand where the water bill would otherwise be substantial — and where you can absorb the upfront drilling and testing cost.
- Consider both. Plenty of sites run a borehole for baseline demand with a mains connection as backup, or the other way around. It doesn’t have to be all-or-nothing.
The right answer depends on details a table can’t capture: your actual peak-day demand, what a hydrogeological survey says about your ground, how long you’ll be growing on that site, and which components the wider system needs. Every job is different.
Not sure? Let’s look at your site
The best water source is the one sized to your actual demand, not a guess. Get in touch to arrange a site visit and we’ll give you an honest opinion on whether mains, borehole or a mix suits your operation.