FAQs, WATER & GEOTHERMAL BOREHOLES

This is in two sections, Water Boreholes, and scrolling lower down, Geothermal Boreholes and Heat Pumps. 

The coloured sections are for general information, you can skip them if you wish.


WATER BOREHOLES

INTRODUCTION

Water is continually moving through the environment – we call this the water cycle. Water evaporates from the oceans, condenses into clouds and then falls on the land surface as rain, only to flow into rivers and back into the sea. However, there is one aspect of the water cycle that is often forgotten – groundwater. Rainfall doesn’t only reach rivers by running off over the land surface.

Most of the rainfall will soak into the soil, which acts like a giant sponge. In the soil some of the water will be taken up by plants and, through a process called transpiration, will return to the atmosphere, but some will soak further into the ground – a process called infiltration - and trickle downwards into the rocks, becoming groundwater. The level at which the rock becomes saturated is called the water table. Water in this saturated zone will flow from where it has infiltrated to a point of discharge. This might be a spring, a river or the sea. Much of the flow of a river will be made up of discharging groundwater, and groundwater provides a vital role supporting wetlands and stream flows.
Water is present almost everywhere underground, but some geological formations are impermeable – meaning that water can hardly flow through them – and some are permeable – they contain fine holes that allow water to flow. Permeable formations that contain groundwater are known as aquifers. The holes that water flows through can be spaces between individual grains in a rock like sandstone, or they can be networks of fine cracks. Very occasionally groundwater will flow in underground rivers, but this is the exception rather than the rule.

Tips on how you can help protect groundwater

You can help to protect the nation’s groundwater resources in a number of ways. For example, by conserving water. This will mean less groundwater needs to be pumped, ensuring resources are available for periods of drought and to help sustain ecosystems that rely on groundwater during summer months, such as rivers and wetlands. Also, by being careful how you dispose of chemicals at home. This will help avoid pollution of groundwater which can have a serious impact on the environment and on the cost of providing water to your house. Another way you can help avoid groundwater pollution is by ensuring that your heating oil tanks at home are regularly checked for leaks.

Here are some tips:

Look at ways that you can conserve water around the house – don’t leave taps running, buy water efficient appliances and fix dripping taps.

Conserve water in the garden. Install a water butt to collect rainwater. Reduce water loss by applying a mulch to flower beds, and by watering plants in the evening when less evaporation occurs.

In many areas garden fertilizer and pesticides can get into groundwater. Always follow manufacturer’s instructions when using garden chemicals, and think about using natural alternatives for pest control.

Dispose of unwanted chemicals, used engine oil and similar materials at a properly licensed Public Amenity waste tip.

Inform the local office of your environment regulator if you are aware of any illegal polluting activities.

Ensure your home heating oil tanks meet the regulations.

Inform the local office of your environment regulator if you are aware of any illegal polluting activities.

Recycle! Recycling paper, plastics and metals can be good for groundwater, as recycling cuts the demand for water in industry.


Frequently asked questions, water boreholes.


1) Q. Can anybody have a water borehole?

A. Almost everybody with a garden, or some free external area, can.


2) Q. Do you dowse for water? 

A. No, we use the help of the British Geological Survey. They provide a scientific, usually accurate prognosis of groundwater depth. i.e. How deep we have to drill. (see links)


3) Q. Do you guarantee to find water?

A.  No,  No reputable company will do this. This is a natural and not always predictable, resource. However, the BGS surveys have proven to be reliable. In the unlikely event that we do not find water on your site, we will charge you only for the drilling time.


4) Q. Do I need a licence or permission?

A. No, Anyone is allowed to extract up to 20 000 litres per day without licence or charge. If you wish to extract more than this, you will have to get an Abstraction Licence from the Environment Agency. (see links). We are in contact with the Environment Agency. We are not aware of any plan to change these provisions.


5) Q. Is it bad for the environment?

A. No, the water that comes from your tap has most probably come from one of your water company's boreholes. We abide by government guidelines.


6) Q. Is groundwater always safe to drink?

A. Usually, but not always. It may have dissolved minerals giving it an unpleasant taste, or, in rare cases be contaminated by external sources. 

We will always recommend that water intended for drinking be tested by our UKAS accredited laboratory. (your local council will also test the water for you on an ongoing regular basis)


7) Q. Do you give long term guarantees for the quality of the drinking water?.

A. No, there is a good reason for this. In the long run you, the end user, are in charge.

We will recommend to you that the borehole water is immediately and extensively tested at our UKAS accredited laboratory (see page on this site). This will allow us to offer you the optimum filtration/purification package for your borehole.

Should you not wish to go to the expense of the tests (several hundred pounds), we will provide you with a standard granulated carbon/UV unit filtration package that will be correctly dimensioned for your water flow requirements. This will be completely adequate in 99.9% of all applications. It is up to you.

We recommend that you have the water tested at regular intervals e.g. annually, to ensure that, however unlikely, no external groundwater contamination factor has arisen.  Use us, or your local council (low cost, even free alternative. Ask for the Environment Officer). However, this is again, up to you.


8) Q. Can you deal with excessive mineral content or contamination?

A. Almost always, yes. Our experts will recommend the appropriate filtration/purification equipment to you.

To avoid external contamination you should be careful to locate your water borehole site away from, and uphill of, any possible contaminant source, e.g. Cesspit, open drainage etc.


9) Q. Is a borehole expensive?

A. We are extremely competitive. The costs will depend on many factors, Depth, Geology, Access for our equipment. Not least upon your requirements regarding storage, outlets, filtration etc. 

You should reckon on at least £5000 for a quality borehole with a minimum of ancillary equipment, i.e. Grundfos pump and automatic controls, HDPE underground wellhead enclosure with access cover, outlet(s). etc.


10) Q. How long will it take?

A. Usually 5-8 weeks from the date of your first enquiry. This assumes that you request a survey from the BGS (recommended!), this will take 3-4 weeks. We will then send you a written quote within 1-2 days. Assuming that you respond quickly to our quote, both parties will sign a clear agreement setting out our obligations to you. We will order the pumping equipment, which is usually in stock. We then spend a week or so on your site (depending on drilling depth and ancillary equipment you require).


11) Q. We haven't got good access, can you get your machine into the garden?

A. Probably yes, we have different drill rigs for different types of borehole. Usually we will need 1.6m free width for access, however, we have had situations where we have stripped down the drill and rebuilt it!.  Call us to explain the limitations and we will tell you if it can be done.                                                       


12) Q. Does it make a mess? 

A. It can, however we have developed (and imported!) sophisticated systems to keep it as clean as possible. If we are drilling in a sensitive environment we will make sure that every effort is made to keep the site clean.


13) Q. Will the noise disturb the neighbours? 

A. Not usually, it is surprisingly quiet and unobtrusive but we all have "those neighbours"!


14) Q. Are the pumps and materials installed guaranteed?, what about maintenance?

A. We use only industry leading Grundfos pumps and Rainbird irrigation components, They are of course covered by the manufacturers guarantee. 

Use of the best components means that our installations are very low maintenance. However, we are only a telephone call away!. (see also Maintenance Schedule page).


15) Q. Does it look unsightly when it's finished? 

A. The wellhead will all be hidden beneath a metal cover, in a custom designed enclosure, under the ground, out of sight. You can even turf it over or lay a patio on it.


16) Q. What components do you use? 

A. We use the acknowledged industry leading equipment for each borehole function.


17)  Q. Should some mishap occur, are you insured?

A. Yes, 

EMPLOYERS LIABILITY:  £10 000 000

PUBLIC/PRODUCTS LIABILITY:  £5 000 000


18)  Q. How can I find my grid reference for the BGS survey?

A. Go to: http://getamap.ordnancesurvey.co.uk/getamap/frames.htm


19)  Q. What guarantees of quality and workmanship do you give?

A. Our workmanship is guaranteed for 2 years. All the components we use are the best we can find. They come with manufacturers guarantees which we pass on to you, the customer.


GEOTHERMAL BOREHOLES & HEAT PUMPS, (GSHP)

INTRODUCTION 

(If you are familiar with heat pump principles you can skip this.)

Although we may not know it heat pumps are very familiar to us - fridges and air conditioners are two examples. Ground source heat pumps (GSHP) transfer heat from the ground into a building to provide space heating and, in some cases, to pre-heat domestic hot water.

For every unit of electricity used to pump the heat, 3-4 units of heat are produced. As well as ground source heat pumps, air source and water source heat pumps are also available.

How does it work?

There are three important elements to a GSHP:

1) The ground loop. This is comprised of lengths of pipe buried in the ground, either in a borehole or a horizontal trench. The pipe is usually a closed circuit and is filled with a mixture of water and antifreeze, which is pumped round the pipe absorbing heat from the ground.

2) A heat pump. This has three main parts:

  • the evaporator - (e.g. the squiggly thing in the cold part of your fridge) takes the heat from the water in the ground loop;

  • the compressor - (this is what makes the noise in a fridge) moves the refrigerant round the heat pump and compresses the gaseous refrigerant to the temperature needed for the heat distribution circuit;

  • the condenser - (the hot part at the back of your fridge) gives up heat to a hot water tank which feeds the distribution system.

3) Heat distribution system. Consisting of under floor heating or radiators for space heating and in some cases water storage for hot water supply.

What options are available?

The ground loop can be:

1)  a borehole or several boreholes;

2)  a straight horizontal trench which costs less than a borehole, but needs more land area and may ruin your lawn/gardens!

3)  spiral horizontal (or 'slinky coil') - which needs a trench of about 10m length to provide about 1kW of heating load.

How much does it cost?

Installation

A typical 8-12kW system costs £8,000-£20,000 plus the price of connection to the distribution system. This can vary with property and location.

Running costs

The efficiency of a GSHP system is measured by the coefficient of performance (CoP). This is the ratio of units of heat output for each unit of electricity used to drive the compressor and pump for the ground loop. Typical CoPs range from 3 to 4 although some systems may produce a greater rate of e. The higher end of this range is for under-floor heating, because it works at a lower temperature (30-35ºC) than radiators. If grid electricity is used for the compressor and pump, then you should consult a range of energy suppliers to benefit from the lowest running costs, for example by choosing an economy 7 or economy 10 tariff.

Ground source heat pumps and your home

What to keep in mind when considering a ground source heat pump.

  • The type of heat distribution system. GSHPs can be combined with radiators but under-floor heating is better as it works at a lower temperature.

  • Is there space available for a trench or borehole to accommodate a ground loop?

  • Is the ground suitable for digging a trench or borehole?

  • What fuel is being replaced? If it's electricity, oil, LPG or any other conventional fossil fuel the payback will be more favourable. Heat pumps are a good option where gas is unavailable.

  • Want to be 100% renewable? Buy green electricity, or install solar PV or some other form of renewable electricity generating system to power the compressor and pump.

  • Need a back-up heating system?

  • Is there also a cooling requirement?

  • Is the system for a new building development? Combining the installation with other building works can reduce costs.

  • Can you incorporate insulation measures? Wall, floor and loft insulation will lower your heat demand.


Frequently asked questions, geothermal boreholes.


a) Q. Do you decide on the depth of the geothermal boreholes?

A. No, this is the job of your GSHP (Ground Source Heat Pump) supplier/installer. We will follow his recommendations.


b) Q. Why should I not take advantage of the package that the Heat Pump company offers?

A. In many cases this will be fine. Beware of mass market suppliers who will take every opportunity to save cost at the expense of long term reliability. Also, some heat pump suppliers take a hefty mark-up on drilling services which they hire in. 

The cost of the boreholes and installed loops is very probably the single largest cost item in the heat pump installation. It therefore pays to come direct to us.

A small example.

The best quality high thermal conductivity Bentonite grout (see below), costs £10-£15 per 25Kg bag. A single typical geothermal borehole will require several dozen bags. Some borehole suppliers then choose to use building plaster mix...

We use high conductivity Bentonite grout:-  

PHYSICAL SPECIFICATIONS

Thermal Conductivity (TC) Range   1.73 – 2.01  Wm-1K-1
Permeability1     <6.9 x 10-8  cm/s
Percent Solids (based on TC)    65.1 – 70.4 %
Grout Weight (based on TC)    1.59 – 1.73 kg/litre
Linear Shrinkage Potential (based on TC)  40 - <3  %
Maximum Particle Size    <300  µm
Unit Yield Range  (based on TC)   131 - 168   litres/unit


c) Q. What guarantees can you give?

A. We buy our grouting materials and PE100, 16bar tested, geothermal loops from reliable, proven British suppliers. They test the loops before delivery. We will pressure test the loops again before we sign off the job with you.

Synergy Boreholes and Systems guarantees the function of the geothermal heat loops it installs for a period of 25 years.

This guarantee is valid under the following conditions.

»The loop is in constant use and does not lie dormant for any period of more than 6 months.

»The loop is not damaged by any external factor or surface disturbance, e.g. garden digging, plowing, other contractors etc. where it is installed.

»The loop is not damaged by any earth movement, slippage, subsidence or other geological factors.

»The loop is at all times filled at the correct pressure, with the correct liquid medium, including the correct amount of antifreeze.

»This guarantee covers only the replacement value of the loop and is capped at £2500 per borehole.

»We can only guarantee what we install, This guarantee applies only to the geothermal loop installed by Synergy Boreholes and Systems Ltd. This guarantee does not cover any other parts of the heat pump installation.


d) Q. Can you recommend a reputable GSHP supplier/installer?

A. Yes we can. We have contact with a few selected suppliers whom we trust to provide high quality service. Please call, or use the email link. We will need your post code to recommend a local installer. (see links on the menu bar below for some reputable GSHP manufacturers/installers)


e) Q. Will it be cheaper to use you to drill the boreholes?

A. Probably, possibly not. What is important is that your heat pump installation gives you many, many years of trouble free operation. 

Remember, the above ground "box" is easy to replace. What is deep under your garden is not.

Ask your potential supplier/installer if he will guarantee the life and performance of the underground GSHP loops (see c above) as well as the heat pump itself.

Should you get a cheap offer for drilling and equipping boreholes, think carefully, ask a lot of questions regarding methods and materials quality. Should you take the offer, be on site to watch the work being done.


f) Q. Will you drill geothermal boreholes for heat pump companies and use their materials or loops?

A. No, this is where some of the larger companies offering the heat pump "package" choose to save money. Should the loop supplied leak when we pressure test it on site, it costs time and money to rectify the situation. Somebody has to pay the extra cost. We prefer to avoid this problem.


g) Q. I wish to have a heat pump/boreholes retrofitted to my house which has access problems, can you do this?

A. We have a very compact, but powerful drill requiring only 1.6m access width, so we can usually find a place to drill. (See equipment/gallery for photos).


h) Q. 'How many boreholes do I need for my installation?'

A. Here is a very approximate way to find out (Please do however, consult your heat pump supplier before making any decisions!)

Sizing of boreholes for a given Ground Source Heat Pump (GSHP) performance.

The use of borehole collectors for GSHPs is necessary when there is insufficient ground area, or limitations on the use of existing ground areas e.g. valuable gardens etc.

Vertical heat collectors usually operate at a higher efficiency, i.e. produce a higher heat yield per metre, than horizontal collectors. They are however, usually more expensive to install than horizontal collectors.

Vertical, i.e. borehole, collectors can provide between 35 and 55 watts per metre of active collector. This figure depends upon the thermal conductivity of the strata in which the borehole is drilled. 

This is one of the reasons that we ask for a geological (BGS) survey of the proposed site. They will give a, usually reliable, projection for this value where you are. Relying on assumptions for this figure, can turn out to be expensive if your new heat pump installation fails to deliver the performance that you expected (and payed for!).

The term active collector is used to denote that part of the geothermal probe which is in direct contact with the ground source, i.e. the high thermal conductivity grout filling in the borehole.

The following calculation can be employed using an average value of 40W/m

Heat Pump capacity in KW  10KW  (Heating, average family 3-4 bed house with reasonable insulation)
Energy provided by ground source   7KW (7000W)
Energy yield per metre of  active collector   40 W

Collector length required is therefore  7000/40 = 175 metres
(This can be one borehole of 175 metres or two boreholes of approximately 90m, (the most usual solution), or three boreholes of slightly less than 60m, should there be e.g. hard rock below this depth.

i) Q. Can I get financial assistance, i.e. a grant to help fund the installation of a GSHP system?

A. Yes you can, up to £1200 from the BERR Low Carbon Buildings Programme.

Left, high quality HDPE pressure moulded bends welded to the bottom of the GSHP loop, (Thermal conductivity in the range 0.35 to 0.4 W/mK). They are designed to withstand the stresses incurred during loop insertion and to offer the least flow resistance to the liquid medium. Middle and right pictures show elements of our computer controlled electrofusion welding capability.