Water Borehole Drilling Across Wiltshire

Borehole Service Utilities Ltd drills private water supply boreholes across Wiltshire, from the chalk of Salisbury Plain to the limestone country around Corsham and Malmesbury. The company works for households beyond the mains, farms, country estates, equestrian yards, nurseries and rural businesses that want a water supply they control. Every job covers the whole sequence: siting the borehole, drilling it, casing and sealing it, test pumping to find the real yield, installing the pump and controls, and treating the water so it is fit to drink.

Wiltshire sits on some of the best water-bearing rock in England. The Chalk Group underlies Salisbury Plain, the Marlborough Downs and the West Wiltshire Downs. The Upper Greensand floors the Vale of Pewsey. Jurassic limestone runs through the north-west of the county, and the Corallian forms the ridge near Royal Wootton Bassett and Calne. Which of those a borehole targets decides how deep it goes, how much water it gives and what treatment the supply needs. Borehole Service Utilities Ltd can be reached on 01428 735013 or at info@boreholeservice.co.uk.

Private water supply boreholes in Wiltshire

A water well borehole gives a Wiltshire property its own water supply, drilled into the aquifer under the site and pumped up to the house, farm or yard. Borehole Service Utilities Ltd drills these for houses off the mains, farms, estates, equestrian yards, campsites, nurseries and rural businesses across the county. The borehole is lined and sealed so surface water cannot get in, then fitted with a submersible pump, storage or a pressure vessel, and controls. Once treatment is in place the water runs through the property's existing plumbing exactly as mains water did.

The reasons people drill in Wiltshire are practical ones. Some properties have no mains connection at all, and the quote to run one across a mile of farmland is worse than the quote to drill. Others are metered and use large volumes on livestock, irrigation or washing down. Estate cottages, converted barns and farm buildings often sit a long way from the nearest main. A borehole removes the metered charge and the standing charge, and it keeps working when a supply pipe elsewhere on the network fails.

Yield is the number that matters. Most single households use far less than 20 cubic metres a day, which is the point at which an abstraction licence normally becomes necessary in England, so a domestic borehole usually sits well inside the exempt limit. Farms, irrigation schemes and boreholes feeding several properties frequently do not. Test pumping shows what the borehole will actually deliver over a sustained period, and the pump, storage and pipework are then sized from that figure rather than from a hopeful guess.

A private water supply borehole tends to suit:

  • Houses and cottages with no mains connection, or an expensive connection route
  • Farms with livestock, dairy washdown, sprayer filling or crop irrigation
  • Country estates with let cottages, farm buildings, gardens and lakes
  • Equestrian yards, liveries, paddocks and gallops
  • Nurseries, growers, campsites and glamping sites
  • Businesses on metered supplies drawing large daily volumes

Which aquifers supply borehole water in Wiltshire?

The Chalk Group is the main aquifer across central, southern and eastern Wiltshire. The British Geological Survey's Devizes memoir states that the principal aquifer within the district is within the Chalk Group. It underlies Salisbury Plain, the Marlborough Downs and the West Wiltshire Downs, so boreholes around Salisbury (SP1 and SP2), Amesbury (SP4), Tidworth (SP9), Ludgershall (SP11), Marlborough (SN8) and Warminster (BA12) are usually Chalk boreholes. As an indicative range, 40 to 100 metres covers most domestic and agricultural Chalk supplies, but the water table decides the real figure: a borehole high on the Plain is considerably deeper than one in the valley bottom at Amesbury or Wilton.

The Chalk is a dual-porosity aquifer, and that has consequences on site. BGS describes unfractured chalk as porous but poorly transmissive: it does not normally drain under gravity, so the usable water moves along bedding planes, joints and fractures widened by dissolution, and that fracturing declines with depth. Drilling deeper is therefore not automatically the answer to a weak hole. Because flow follows fractures, the aquifer responds quickly to rainfall and turbidity can spike after a prolonged wet spell. BGS also records solution features and sinkholes in the Devizes district, which concentrate recharge and raise contamination risk, so headworks protection is not a formality.

West and north-west Wiltshire sit on different rock again. The Upper Greensand floors the Vale of Pewsey and outcrops in a strip along the foot of the chalk escarpment through Potterne, Market Lavington, Urchfont and Coulston in the Devizes area (SN10), and behind Westbury and Bratton (BA13). BGS calls it an important minor aquifer in southern England, highly permeable with intergranular flow predominating, and gives its thickness in the Devizes district as 25 to 40 metres. The Gault beneath it acts as an aquiclude and throws out the spring line that keeps flowing through long dry periods. Fine sand carry-over is the usual complaint in a poorly developed borehole.

The formations a Wiltshire borehole is likely to meet, with indicative depth ranges rather than fixed figures:

  • Chalk Group — Salisbury Plain, the Marlborough Downs, the West Wiltshire Downs and the Chalke, Wylye, Nadder and Bourne valleys. Broadly 40 to 100 metres. Hard water, fracture-fed, quick to respond to rainfall.
  • Upper Greensand Formation — the Vale of Pewsey around Devizes (SN10) and Pewsey (SN9), the foot of the west Wiltshire scarp, and the Vale of Wardour margins. Broadly 25 to 70 metres. Highly permeable, with fine sand to manage.
  • Great Oolite and Inferior Oolite limestones — the Bath stone belt at Corsham (SN13), Box, Colerne, Castle Combe and Biddestone (SN14), Bradford-on-Avon and Monkton Farleigh (BA15), and north to Malmesbury and Sherston (SN16). Broadly 30 to 80 metres. Very hard water, fissure flow, low storage.
  • Corallian Group — the ridge through Royal Wootton Bassett (SN4) and the Calne area (SN11). Broadly 30 to 70 metres. BGS and Environment Agency baseline work gives typical borehole yields of 25 to 85 cubic metres a day, which suits a house, a smallholding or modest irrigation rather than a large abstraction.
  • Portland and Purbeck limestones — the Vale of Wardour at Tisbury, Chilmark, Chicksgrove and Dinton (SP3). Broadly 20 to 60 metres. Thin, fissured and compartmentalised: useful for a property or a farm, not for large volumes.
  • Gault, Lower Greensand, Oxford Clay and Kimmeridge Clay — the clay vales around Trowbridge (BA14), Melksham (SN12) and Chippenham (SN15). Not water supply targets. BGS calls the Lower Greensand here a poor aquifer providing poor quality water. These are horizons to case through.

What happens on site, from survey to commissioning

Every borehole starts with a desk study before a rig goes near the site. That means checking the geology under the property, the records of nearby boreholes, the depths at which water has been struck locally, and where the borehole can sit so it is protected from surface contamination, reachable for servicing, and clear of drains, soakaways and buried services. Access matters too. A drilling rig and its support vehicle need a route in and a working area, and the position that suits the plumbing is not always the position that suits the ground.

Drilling a domestic borehole usually takes a few days, with deeper or more difficult holes taking longer. Steel casing is set through the topsoil, drift and weathered rock and grouted in, which seals the borehole against surface water and shallow contamination. Below that the hole may be left open in competent rock, or screened and gravel packed where the formation is loose or sandy. The borehole is then developed by airlifting to clear fines and open up the fissures feeding it, and test pumped over a sustained period to measure yield, drawdown and recovery.

The pump and controls come after the test, not before. Sizing follows the tested yield and the property's peak demand, so the pump matches the borehole instead of overdrawing it. A normal installation is a submersible pump in the borehole, a rising main, a protected headworks chamber, a control panel with level protection, and storage or a pressure vessel in the house or plant room. Treatment is fitted at the same time. Before handover the supply is chlorinated, flushed and sampled, and the ground is reinstated so the finished headworks sits flush and lockable.

The stages of a borehole installation, in order:

  • Desk study of the geology and nearby borehole records, then siting on the ground
  • Drilling, with steel casing grouted through the shallow ground
  • Screen and gravel pack where the formation calls for it
  • Development by airlifting to clear fines and open the water-bearing fissures
  • Test pumping to establish yield, drawdown and recovery
  • Pump, rising main, controls and storage sized to the tested yield
  • Filtration and disinfection specified from the water analysis
  • Chlorination, flushing, sampling, handover and reinstatement

Do you need a licence to drill a borehole in Wiltshire?

In England an abstraction licence from the Environment Agency is needed to take more than 20 cubic metres, or 20,000 litres, of groundwater a day. Taking 20 cubic metres a day or less does not require a licence. Where water is taken from the same source at more than one point, it is the combined total that has to stay at or below 20 cubic metres. In practice a single household sits comfortably under the threshold, while farms, irrigation schemes and boreholes serving several properties frequently do not.

Notification is a separate duty. Under section 198 of the Water Resources Act 1991, anyone proposing to sink a well or borehole intended to reach more than fifty feet, about 15 metres, below the surface in order to search for or abstract water must give notice before starting. Notice goes to UK Research and Innovation, in practice the British Geological Survey. A journal of the work recording strata and water levels must be kept, a complete copy sent on completion or abandonment, and particulars of any flow test supplied. Failing to do so is an offence, carrying a fine up to level 3 on the standard scale plus a further £20 for each day the offence continues after conviction.

Where a licence will be needed, government guidance says a groundwater investigation consent from the Environment Agency may also be required before the investigation borehole is drilled, so speak to the Agency early. The Agency publishes abstraction licensing strategies showing where water may be available in each catchment, and advises checking the strategy before applying. Once a supply is in use it falls under the Private Water Supplies (England) Regulations 2016, as amended in 2018. The local authority, Wiltshire Council across most of the county and Swindon Borough Council for the Swindon unitary area, must risk-assess every private supply, review that assessment at least every five years, and sample on that basis.

Filtration, treatment and borehole maintenance

Wiltshire groundwater is hard, and treatment starts from that fact. BGS records generally hard groundwaters in this part of the country, up to 300 mg/l as calcium carbonate, and over 1,000 mg/l from some confined limestone units. Hardness is not a health problem in itself, but it furs kettles, cylinders, showers and pipework, so limescale reduction or softening is a normal part of a Wiltshire installation. Nitrate is the standard indicator of arable land above the aquifer and should always be tested for on the downland.

The treatment specified follows the water analysis rather than a catalogue. Sediment filtration plus UV disinfection is the usual minimum on fissured aquifers, because both the Chalk and the north-west Wiltshire limestones respond quickly to rainfall and can carry turbidity after a heavy or prolonged wet spell, and UV cannot work properly through cloudy water. Iron and manganese turn up where a borehole is confined beneath clay, and BGS notes that water from the weathered top of the Oxford Clay is often ferruginous. pH correction is added where the water is aggressive to copper pipework.

A borehole is a mechanical installation and needs servicing like any other. Borehole Service Utilities Ltd services pumps and controls, investigates falling yield, rising sand or sediment, tripping pumps and failed water samples, and carries out downhole CCTV surveys where the cause is not obvious from the surface. Plenty of boreholes that look dry are nothing of the kind: a blocked screen, a scaled or worn pump, a leaking rising main or a collapsed section will all cut output. Rehabilitating an existing borehole is often quicker and cheaper than drilling a replacement.

Typical treatment on a Wiltshire private supply:

  • Sediment and particle filtration for fines and post-rainfall turbidity
  • UV disinfection to deal with bacteriological risk
  • Iron and manganese removal where the analysis calls for it
  • pH balancing where the water is acidic or aggressive to pipework
  • Limescale reduction or softening for hard Chalk and limestone water
  • Sampling, cartridge changes, UV lamp replacement and pump servicing on a set programme

Irrigation boreholes for gardens, sports grounds, farms and nurseries

Irrigation is one of the biggest reasons landowners drill in Wiltshire, because peak summer demand is exactly when mains water costs most and is most likely to be restricted. Borehole Service Utilities Ltd supplies irrigation boreholes for gardens and estate grounds, sports pitches and golf courses, nurseries and growers, and farms watering crops or filling sprayers. The demand pattern is nothing like a house: a heavy draw for a few hours a day for part of the year. The borehole, the pump and usually a buffer tank are therefore sized around peak seasonal demand rather than average use.

Wiltshire has the land use to match. The BGS Wincanton district memoir records watercress growing at Hill Deverill near Warminster (BA12) as over 32 per cent of licensed groundwater abstraction in that district, with fish farming a further 8 per cent or so, which is a fair measure of what a commercial growing operation actually draws. The county's estates run similar demand at a different scale: Wilton House near Salisbury covers around 14,000 acres in 14 farms with more than 200 residential properties, and Longleat near Warminster has about 4,000 acres of let farmland alongside its parkland. Racehorse yards and gallops on the Marlborough Downs at Beckhampton and Manton add their own year-round demand.

Irrigation is the use most likely to cross the 20 cubic metre a day threshold, so an abstraction licence is a live question from the outset rather than an afterthought. Where a borehole feeds both a property and an irrigation system from the same source, it is the combined abstraction that counts towards the threshold. It is worth costing the whole scheme rather than the hole alone: storage, filtration where water passes through sprinklers and emitters, and a control system that can run the programme overnight when evaporation losses are lowest.

Soakaway boreholes for surface water drainage

A soakaway borehole disposes of surface water by drilling through ground that will not take it and into a permeable layer below that will. In the north and west Wiltshire clay vales, on the Oxford Clay and Kimmeridge Clay around Trowbridge (BA14), Melksham (SN12) and Chippenham (SN15), percolation tests routinely fail and a conventional soakaway trench simply fills and stays full. That is the standard reason a deep borehole soakaway becomes worth considering on a new building, an extension, a farmyard or a large area of hardstanding.

The design work is the same discipline as a water borehole in reverse. The ground profile decides where the receiving horizon sits and how deep the borehole must go to reach it. The borehole is cased and sealed through the shallow ground so it takes water only where intended, and a silt trap or catchpit is fitted ahead of it, because a soakaway borehole that silts up is a soakaway borehole that has stopped working. What goes into it matters just as much: clean surface water only, never foul drainage, since the horizon it discharges to may be somebody else's water supply.

Notification applies here too. BGS states that the section 198 duty to notify covers deep soakaway boreholes as well as abstraction, trial, monitoring and observation boreholes, so a soakaway borehole intended to go more than about 15 metres down must be notified before work starts and recorded afterwards. Discharges of surface water to ground can also fall within Environment Agency permitting, particularly on commercial sites and yards where run-off may pick up silt or oil, so that should be checked for the site before the design is fixed.

Off-grid solar borehole pumps for remote Wiltshire properties

An off-grid borehole uses a solar-powered downhole pump to lift water where there is no practical mains electricity to run a conventional one. Borehole Service Utilities Ltd installs solar-powered submersible pumps for remote properties, livestock troughs, field taps, isolated cottages and farm buildings across Wiltshire. The panels feed a controller, the controller drives the pump, and the water goes to a storage tank sized to carry the property or the stock through dull days and overnight. It is a water supply system: the solar array is there to run the pump, nothing else.

Wiltshire has no shortage of places where this makes sense. Salisbury Plain is a chalk plateau of about 300 square miles, and the Ministry of Defence owns 150 square miles of it, roughly 11 per cent of the county, much of that let to farmers or grazed under licence. Add the downland holdings around Tidworth (SP9) and Ludgershall (SP11), and the estate and farm property in the valleys around Downton (SP5), Tisbury (SP3) and Mere (BA12), and there is a great deal of land where the nearest usable power supply is a long way off.

Sizing is the whole job. Daily demand, the lift from water level to tank, the pipe run, panel output and tank capacity all have to work together, and the honest way to do that is from the tested yield of the borehole and a realistic count of what the property or the stock actually draws. Storage does the heavy lifting: a larger tank filled slowly beats a larger pump run in bursts. Where a mains connection exists but is unreliable, the same arrangement can sit alongside it as a backup.

Borehole drilling by town and postcode in Wiltshire

These are the 22 main towns and postcode districts Borehole Service Utilities Ltd covers in Wiltshire. The surrounding villages and outlying farms in each of these districts are covered too, so it is worth ringing even if your own village is not named here.

  • Salisbury – SP1, SP2
  • Trowbridge – BA14
  • Chippenham – SN14, SN15
  • Devizes – SN10
  • Marlborough – SN8
  • Warminster – BA12
  • Melksham – SN12
  • Calne – SN11
  • Corsham – SN13
  • Westbury – BA13
  • Bradford-on-Avon – BA15
  • Malmesbury – SN16
  • Amesbury – SP4
  • Royal Wootton Bassett – SN4
  • Tidworth – SP9
  • Ludgershall – SP11
  • Cricklade – SN6
  • Pewsey – SN9
  • Mere – BA12
  • Wilton – SP2
  • Tisbury – SP3
  • Downton – SP5

Borehole Questions from Wiltshire Property Owners

Depth depends on the aquifer under the site. On the Chalk of Salisbury Plain, the Marlborough Downs and the Salisbury area, 40 to 100 metres is an indicative working range. On the Upper Greensand of the Vale of Pewsey it is nearer 25 to 70 metres, and on the Jurassic limestones around Corsham and Malmesbury 30 to 80 metres. The water table position decides the real figure, so a borehole high on the downs is deeper than one in a valley bottom.

An abstraction licence from the Environment Agency is needed only if more than 20 cubic metres, or 20,000 litres, of groundwater a day is taken. Below that no licence is required. Where water is taken from the same source at several points, the combined total must stay at or below 20 cubic metres. Most single households are well under it. Farms, irrigation and multi-property supplies often are not, and a groundwater investigation consent may also be needed.

Yes. Under section 198 of the Water Resources Act 1991, anyone proposing to sink a well or borehole intended to reach more than fifty feet, about 15 metres, below the surface to search for or abstract water must give notice before work begins, to UK Research and Innovation, in practice the British Geological Survey. A journal of strata and water levels must be kept, a copy sent on completion, and flow test particulars supplied. BGS says the duty also covers deep soakaway boreholes.

Yield is settled by test pumping, not by depth. A well-sited borehole in the Chalk or the Jurassic limestone can supply a house, a farm or an irrigation system, because the water comes from fractures rather than from the rock matrix. The Corallian around Royal Wootton Bassett and Calne is more modest: BGS and Environment Agency baseline work gives typical yields of 25 to 85 cubic metres a day. Yields vary over short distances in fissured rock, so a weak borehole nearby proves little about your site.

Borehole water is safe to drink once it has been tested and treated correctly. Wiltshire's aquifers are fissured, so they respond quickly to rainfall and can carry turbidity and bacteriological risk after heavy rain. Sediment filtration and UV disinfection are the normal minimum, and nitrate should be tested for under arable downland. The finished supply is regulated as a private water supply, with the local authority risk-assessing it, sampling on that basis, and reviewing the assessment at least every five years.

Yes. Chalk and limestone groundwater is hard calcium-bicarbonate water. BGS records generally hard groundwaters in this part of the country, up to 300 mg/l as calcium carbonate, and over 1,000 mg/l from some confined limestone units. Hardness is not a health risk, but it scales kettles, cylinders, showers and pipework, so limescale reduction or softening is usually fitted. Iron can also appear where a borehole is confined beneath clay, and is dealt with by filtration.

Most domestic boreholes are drilled within a few days, with deeper or more difficult ground taking longer. Drilling is only part of the programme. Casing and grouting, developing the borehole by airlifting, test pumping over a sustained period, installing the pump and controls, fitting treatment, then chlorination, flushing and sampling all follow. Allow longer overall than the drilling alone, and remember the rig and its support vehicle need an access route and a working area.

Yes. Many Wiltshire properties keep the mains and add a borehole for the volume uses, such as irrigation, livestock, washing down and filling tanks, while others run everything from the borehole and hold the mains as a backup. The two supplies must be kept physically separate, with no cross-connection. Wessex Water supplies the mains across most of Wiltshire and Thames Water covers Swindon and the north of the county.

A soakaway borehole disposes of surface water by taking it through ground that will not accept it into a permeable layer below. It is the usual answer where a percolation test fails, which is common on the Oxford Clay and Kimmeridge Clay around Trowbridge, Melksham and Chippenham, where the clay drains badly. It is cased and sealed through the shallow ground and fed through a silt trap. Clean surface water only: foul drainage must never be discharged to a borehole.

Talk to Borehole Service Utilities Ltd about a Wiltshire borehole

Borehole Service Utilities Ltd works across Wiltshire, from Salisbury, Amesbury and Tidworth on the chalk to Chippenham, Corsham, Malmesbury and Bradford-on-Avon on the limestone. Call 01428 735013, or 07970 573840 and 07517 151270 for a mobile, or email info@boreholeservice.co.uk. Say where the property is, what the water is for and whether there is a mains connection, and you will get a straight answer on what the ground under you is likely to give and what the work involves.