Ground source heat pump: loops, boreholes and permits

With enough land, the ground loop goes into trenches, either as straight pipes or as coiled 'slinky' loops. MCS notes that these trenches are typically between one and two metres deep, and that the garden needs to be suitable for digging and reachable by machinery. A paddock or large lawn is ideal; a small town garden usually is not.

Where space is tight, the loop goes into vertical boreholes drilled by a specialist rig. Boreholes take up little surface area and reach ground that stays at a steady temperature, but drilling is expensive and the ground conditions, access for the rig and disposal of spoil all affect the price. A borehole design should be based on local geology, not a rule of thumb.

Shared ground loops, where several homes connect individual heat pumps to a common array, are another route, often used in blocks of flats or small developments. The Boiler Upgrade Scheme can fund heat pumps on shared ground loops.

Planning Portal describes ground source and water source heat pumps on homes as usually permitted development in England. Listed buildings and conservation areas should check with the council first, and archaeology or tree roots can matter for trenches.

The bigger question in England is the environmental permit. A new closed-loop ground source system installed on or after 2 October 2023 must either meet the Environment Agency's exemption conditions for low environmental risk settings, meet the conditions of regulatory position statement RPS 307 for a single system serving residential premises, or have a permit. Open-loop systems that draw water from the ground are regulated separately. Your installer should tell you which route applies before drilling starts. Scotland and Wales have their own environmental regulators and rules.

Source: gov.uk · planningportal.co.uk

Approved Document L sets out how the ground loop should be commissioned: the ground arrays and headers flushed and purged of air, the heat pump flushed separately, a pressure test on the whole closed-loop system, and antifreeze and biocide added as the manufacturer specifies. You should be given details of the fluids used and their concentrations. A quote that does not mention flushing, purging and pressure testing is missing part of the job.

Ground source systems cost considerably more than air source, largely because of the groundworks or drilling. In return they tend to run more steadily in cold weather because the ground temperature changes little through the year.

Until 31 March 2027, the installation of ground source heat pumps in homes is zero-rated for VAT, and HMRC's notice extends that to the groundworks needed to install the pipework. The Boiler Upgrade Scheme grant for a ground source heat pump is the same as for air source.

• trench length and depth, or number and depth of boreholes
• who does the drilling or digging, and how spoil and reinstatement are handled
• the environmental permit route: exemption, RPS 307 or permit
• ground loop fluid, pressure test and commissioning record
• heat pump model, cylinder, and any radiator changes indoors

Source: gov.uk

Describe the plot, access for machinery and the current heating. Once your number and email are confirmed, ground source installers in your area see the job without your personal details, and only one of them can buy it. That installer pays Offrano; you do not.

Before they see who you are, we email you their name, address and phone number. No installer is obliged to take the job, and unsold requests are withdrawn after 21 days. We check that the buyer is a registered business, not how it designs ground arrays, so check its MCS certification and ask about similar sites it has completed.