Choose boreholes when…
Ground space is tight, the project spans several properties, or you want the most efficient collector in the ground and access for the rig works.
Ground source basics
Boreholes, trenches or a pond: choosing your ground collector.
Every ground source heat pump draws its warmth from a collector — pipework buried in the ground or submerged in water. There are three main types, and the right one depends on your land, your budget and how much heat your property needs. Here is how they compare.
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20+ years' experience
4,000+ systems since 2006
In-house drilling teams
The basics
What a ground collector actually does.
A ground collector — sometimes called a ground array — is the buried pipework that gathers low-grade heat from the earth or from water and carries it to your heat pump. The pipes circulate a water and antifreeze mixture, often called brine, and the heat pump's compressor lifts the collected energy to a usable temperature for your heating and hot water.
The same collector can do more than heat your home: we also use ground arrays to provide passive and active cooling, and to store excess energy from solar thermal systems back in the ground. The groundworks are a large part of a ground source installation's budget, but the buried pipework has a design life measured in decades and typically outlasts the heat pump it serves — see how a full ground source system fits together.
Vertical collectors
Boreholes: the most heat from the least land.
Vertical collectors sit inside one or more boreholes drilled to around 100 metres, each only about 20cm wide. They suit properties with limited ground space — and housing developments, where a shared ground array lets one borehole field serve two or more homes.
Drilling needs specialist equipment, which makes boreholes the most expensive collector to install, and the process is genuinely messy — muddy water and cuttings come out of the hole, which catches many people by surprise. Our own in-house rigs and drilling teams do the work, so you are never dealing with a subcontractor. A borehole can sit close to the property without causing damage (we recommend within 25 metres), and allowing around a week covers drilling two boreholes including rig set-up and take-down. In return you get arguably the most efficient collector in the ground.
Horizontal collectors
Trenches: straight pipe or slinky coils.
Horizontal collectors are laid in trenches around 1.2 metres deep and suit properties with plenty of surrounding land — smallholdings and agricultural properties especially. They come in two forms: straight pipe in long, narrow trenches, and "slinkies", coiled loops of smaller-diameter pipe in wider but much shorter trenches.
Straight pipe is the more efficient of the two but needs room — runs of around 100 metres out and back, in ground free of obstructions like tree roots. Slinkies need around five times less groundwork and fit far more gardens and field shapes, but the coil layout is less efficient, so more pipe goes in the ground overall to compensate. Either way you need space to hold the excavated earth while the pipes are laid, and in poor ground a sand bed above and below the pipe protects it from sharp stones. If you have your own digger or groundworker, horizontal collectors can be the cheapest option; at contractor rates the cost can approach a borehole.
Water collectors
Lake collectors and pond mats: the quiet bargain.
A nearby lake or large pond may offer a suitable heat source. We assess water temperature, depth, volume, permissions and the pipe route before recommending it. The source temperature is site-specific, so a water collector cannot be assumed to return warmer fluid than every ground collector.
That makes lake collectors and pond mats the most cost-effective collector of all, and they suit any property the water source can serve — houseboats included — provided the water holds enough pipework for the heat load. The water needs to be at least 1.2 metres deep so it cannot freeze, and the pipework needs protecting from boats, propellers, waves and fouling. The collector is assembled on shore, floated into position, then sunk to the bed on weights or corrosion-resistant stainless steel frames. More about water source heat pumps.
Which one is right?
Designed from your site, not from a brochure.
The right collector depends on your budget, the heat load your property needs, the ground around it, the space available, how many properties or facilities need heat, and the system design itself. We carry out a site visit and a heat-load report so the collector is sized for your project, not assumed.
Choose trenches when…
You have generous, unobstructed land — especially if you have your own digger, which can make horizontal collectors the cheapest route.
Choose water when…
A deep-enough lake or pond sits within about 50 metres. It is the most cost-effective collector and the warmest return temperatures of the three.
Keep exploring
Go deeper on ground source.
Not sure which collector fits your land?
Tell us about your property and we'll advise honestly — including a site visit and heat-load report before anything is designed.