The Drilling Process

The final stage of the sequence of events is to pump and pipe (reticulate) the water from the successful borehole.  The end use of the water will to a large extent determine what type of pumping and reticulation system is to be installed.  Of paramount importance to the pump installer are the results of the pumping (or yield) tests – how much water can be pumped out the borehole for how long a period? That is, what is the sustainable yield of the borehole.

General factors influencing the size of the pump to be installed will be the following:

• The clients’ water demand.
• Depth of the hole.
• Actual water yield of the borehole

Depending on the geological formation, there should be a borehole rest period before the pump can be installed. The drilling contractor will advise the client accordingly.

How long does the pump installation take?

Borehole installation with a pump can take about a day or two. Connected to a tank system, the borehole installation can take a further 2 days.

Will my borehole need a pump?

Usually, yes. A submersible pump is electrically operated pump which is located at the bottom of the borehole to bring water to the surface. However, if the underground supply is under pressure, this creates an artesian well where water simply flows out, and which does not require a pump.

How reliable is a submersible pump?

We only install high-specification equipment and they are very reliable. But a number of operational factors have an influence, such as low mains voltage. “Aggressive’ water, which is exceptionally acidic or alkaline, can have an impact as well. However, replacing a pump is normally a straightforward process—small domestic type pumps are suspended on a nylon rope to enable it to be brought to the surface. The changeover time will usually take anything from 3 hours to 5 hours on-site.

What is a yield test and should I have it done?

A yield test determines the amount of water in the borehole and the rate at which it can be pumped. It is useful to have a yield test done in order to determine the correct size of your submersible pump. A well selected submersible pump will give you many years of good service. After the testing is completed, a certificate indicating that the yield is tested, is provided.

Will the borehole yield always be the same?

The yield of a borehole is not always constant. Precipitation conditions above the ground will determine the availability of water in the borehole. Natural fluctuations in the weather systems such as seasons and drought will impact on the yield of a borehole. It is better to drill your borehole in the driest time of the year as that often gives one an indication of the worst case scenario.

Do I need filtration?

The answer to this question depends on the results of your water analysis tests. If you’re water test results shows no adverse content whatsoever, we would always recommend a 3-phase sediment filter and a simple ultra violet filter at the point of use if you intend to drink it. However, if you’re pumping directly to an irrigation system for example, usually no filtration is required. In case the pH is not favourable an adjustment may be necessary to protect your irrigation equipment.

Other forms of filtration for example, might be if your test results show high levels of iron, manganese, lead, or any one of a host of other metals, or if your water is excessively hard or soft.

What is a pressure vessel and do I need one?

A pressure vessel is a pressurised cylinder which attempts to maintain equilibrium of even water pressure (Bar) across a system which has several or many points of use. If your storage tank pump is going to deliver water to 3 or more points of delivery, using water at one point may cause a sudden drop in pressure at another point.

This may or may not be a problem depending on what you’re using the water for. Some uses may be pressure sensitive or critical whilst others are not affected by drops in pressure. We have all experienced being in a shower, happily lathering yourself, and somebody turns a tap on. Whilst this is far from critical and is simply unpleasant, if you’re using equipment which is pressure sensitive or critical, maintaining even system pressure (Bar)across your network may be essential.

Do I need a tank and if so what size?

For most scenarios we always recommend a water storage tank. This tank, or series of tanks may be sited above ground under cover. Tanks above ground which are not under cover will either need to be shielded from frost – or built of a special type which resist frost. Installing storage tanks offer distinct advantages over pumping directly from a well or bore. The heart of your system is your bore or well pump. It is often the single most costly item in the system and is beneficial not to have this pump switching on and off every time there is demand. Instead it is better to pump your well or bore water to a tank – a second stage if you will, from which your water is then delivered to your network via a tank pump.

Tank size is calculated as a portion of your water requirements. For example, if you need 2 500 litres a day and your system suddenly develops a problem, you either have to do without water until the system has been repaired, or you must switch back to mains water – if you have mains. A 2 500 litre tank means you can continue using your water, and have a day in which to isolate and fix the problem.

Suddenly finding yourself without water may be inconvenient if the water is simply for a home situation, but if you’re pumping water for commercial use, this could be costly to your business. Having a storage tank which can store a portion of your water needs gives you time. You can continue operating as you effectively have a reserve. A storage tank buys you time to get any problem fixed, enables you to continue using your water, reduces stress on your bore or well pump by not have it operating constantly – and in general gives your better control over you entire system

How will my borehole water compare with mains water?

As far as the supply itself is concerned, water is pumped from the borehole at a constant ‘mains’ pressure, typically 2-4 bars. With an adequate supply, there is no requirement for storage tanks. The pump supplies water ‘on demand’, and a pressure-operated switch cuts off its electricity when it is not working, to ensure economic running. We run pipework to your building exactly as a rising mains supply would be connected, so in general your water is a ‘fit and forget’ installation

What is groundwater recharge?

When the water level of the borehole drops it is recharged with water entering the borehole from the cracks and fissures or aquifer. Water under the surface of the earth (groundwater) occurs in cracks and fissures in hard rock formations across about 89% of the RSA. The other 10% is underlain by loose sands (also called primary aquifers) where the water occurs in openings between sand grains.

How can Borehole Water be contaminated?

Bore water can be naturally contaminated by minerals, chemicals, bacteria and viruses. However, human activity usually has the greatest impact upon shallow ground water quality as a result of:

• Excessive or inappropriate use of fertilizers, animal manures, pesticides and insecticides;
• Poorly constructed and maintained septic tanks and other liquid waste disposal systems;
• Pit toilets
• Leaking fuel and chemical tanks;
• Intensive agriculture, industry or mining;
• Leaching from waste disposal areas; and
• Accidental spills of chemicals
• Feedlots and kraals
• Other contaminants such as nitrate, arsenic, pesticides and petroleum products are of health concern, particularly if bore water is used for drinking or watering vegetables.

It is not always possible to tell if your bore water is contaminated. However some signs of potential trouble are:

• A low pH (acid water);
• A chemical or petrol smell;
• Soap suds around sprinkler outlets;
• A change in water colour; and
• Dying or wilting plants.

It is possible to do a simple test for pH (acidity) by using either a swimming pool test kit or pH test strips. This will show if the bore water has the ability to dissolve either man made or naturally occurring substance in the soil.

Bore waters with a low pH (acidic) of less than 5 should be professionally tested to ensure that they are safe to use.

How long will a new borehole last?

Several generations at least. Our boreholes are lined with tough plastic pipe to the bottom which allows water to flow into the borehole and prevent the bore from collapsing.

Can an existing hole be rehabilitated?

Difficulties can arise particularly with old ones, where the use of steel pipe work often causes corrosion difficulties. And where mild steel is used there can be encrustation and premature failure.

Careful design eliminates many problems at source. For example, the hallmark of a good borehole is that the velocity of water entering through the screen travels as slowly as possible. The problem being addressed is that water that is moving rapidly is likely to drag in sediment and debris, which can cause the migration of silts and sand and again this can result in premature pump failure. Also, fast-moving water can abrade the screen.