Building Construction, Renovation & Maintenance

Bore Wells

I have a close relative who has worked all his life in the catering industry. He never eats backso (meatballs), that ever so popular local delicacy, because he once went to a factory and had the questionable pleasure of seeing how it is made. All the squiggly bits you would never normally eat are ground up along with a good healthy dose of industrial chemicals to make those local meatballs and sometimes the hygiene standards are as questionable as the table manners of the Alaskan hyena.

The origins of what we put in our mouths is all too often obscure to say the least as those delicious horsemeat burgers of Europe are suddenly proving.

Where does your water come from?

Never mind bakso and other food stables (sorry, I mean staples), it is amazing how many people have no idea where their water comes from. Most of us know better than to drink local water or clean our teeth in it but we still wash our dishes and ourselves in it (well some of us do) without knowing where it comes from. Some of us are fortunate enough to have a government reticulated water supply from PDAM (Perusahaan Daerah Air Minum which translates as regional drinking water company). This is supposed to be fairly safe however, due to the many leaks in the pipes of the distribution network, we have to assume there can be contamination from the surrounding groundwater which, in many areas is close to septic tanks along the way.

Many of us, whether we know it or not, get our household water from a well or, far more likely these days, a bore.

What is a bore well?

A bore is a hole, usually 4 or 6 dim, drilled into the ground. A pump is put at the bottom to pump water to our house. It is, in effect, a small diameter well but there are fundamental differences that make a bore more attractive than a well. The kids can’t fall down it for a start.

But first I used the word ‘dim’, this is not a measure of IQ of the average bore but is, in fact, a highly technical local term used by a population that want to use ancient imperial measurements in a metric world without anyone finding out. 4 dim actually means 4 inches diameter. Plumbing pipework in Indonesia is still usually measured in inches, those strange units of measurement that somehow feel just right and certainly are not like those miserable little centimetre things. Inches of course were first found by the dozen on Roman’s feet. Just to be belligerent the Scots had their own inch, a twelfth of a Scotsman’s foot and if you think Roman’s have big feet you’ll find Scottish feet are even bigger. All due to natural selection of course, in Scotland people with small feet sank into the peat bogs long ago never to be seen again.

Inches are useful things too, if you don’t have a ruler an inch is the width of a man’s thumb (is that where rule of thumb came from?) and you’ve always got your thumbs with you, not like those hopeless centimetre things which are, of course, the distance between the eyeballs of the common European brown rat, no ruler - first find a rat…..

Anyway here in Indonesia, as you would expect, the size of our pipes is related to the size of a Roman’s foot.

Probably the greatest advantage of a bore is depth. I recently came across a well being dug by a team of welldiggers. 1 metre (III.·. Roman’s feet) in diameter the diggers got down 15 metres (XLI?. Roman’s feet) when the air got so foul that the digger at the bottom was passing out and the well digging had to stop and the well, still dry, was abandoned. The moral of this is that if you are digging a well don’t have beans for breakfast.

Bores are drilled by a boring machine and can go much deeper than wells without being affected by noxious fumes.

A typical bore in Bali can be anything from 20 to 50 metres deep. In some areas such as the Bukit bores may go much deeper and 130 metres is not unusual. How deep depends on where you are and the type of land you are in. For most of us the ground is alluvial deposits so we drill our bore through clays and soils. On the bukit the ground is limestone which is full of fissures and cavities, the water flows away easily and so the surface of the groundwater is deep within the rock. On the bucket to get water you have to drill down virtually to sea level and there you can get clean fresh water if you are not too close to the sea.

Bores provide filtered water

Bores and wells work in the same basic way. We put a tube into the ground to achieve two aims: firstly to give us access to water that lies deep within the earth, secondly to collect clean water that has been filtered by flowing down through the earth. The first aim is obvious, the second depends on sealing the sides of the tube so that water has to flow down through the earth before it can enter through the bottom of the tube.

To install a bore we drill a hole and we slide a pipe or a sleeve down the hole to seal it. This sleeve must not go right to the bottom of the bore, it has to have enough bare earth at the bottom to allow the water to seep into the hole as fast as you are going to pump it out. In a 50 metre deep bore we might put in a 45 metre long sleeve giving us a healthy 5 metres of open hole at the bottom to collect water.

How to find water

But first we must find some water and this can be a bit of a hit and miss affair. You can do it the old fashioned way by calling in a water diviner, usually a crusty old bloke with hairy eyebrows who wanders around delicately holding a twig or clutching his scrotum until he ‘feels’ the twitch of the water. These days you can be far more scientific and have a hydrogeological survey done, expensive but far more reliable and, if water is key to your business success, then perhaps the cost is well justified. Drilling bores can be expensive particularly through rock, doing a proper survey beforehand makes sense.

But then there are of course those mysterious things ‘aquifers’, water bearing rock, the holy grail of the water diviner. If you hit an aquifer you can usually find a good source of water but aquifers may have a downside. An aquifer may have fairly freely flowing water in an underground stream and is more likely to be polluted than water that has been filtered by seeping slowly down through the earth. Years ago I came across a man in Canggu who had a bore which, at 50 metres, was fairly deep for a ricefield area. We tested his water and found serious lead contamination. In an area like this the lead was most likely coming from some man made pollution, perhaps a bengkel with old car batteries somewhere upstream. He had happened to hit an underground stream. The solution was to drill the bore a bit deeper or even shallower to avoid the problem water source.

Bore wells require submersible pumps

Alright so we have found the right place, drilled a hole and put in a sleeve, all we have to do now is get the water out but we have a problem. A normal water pump is probably good for moving water up to say 10 metres (it varies depending on the pump). Also water pumps are far better at pushing water up a pipe from the bottom rather than pulling water from the top. How do we get water up from the bottom of a 50 metres deep hole?

Special types of water pumps have been developed for use in bores over say 20 metres where normal pumps simply aren’t up to the job. These pumps go at the bottom of the bore to push the water out. But just a minute, a bore is usually only 4 or 6 dims wide (a third or a half of a Roman’s foot) not only that the bore is full of water at the bottom.

These pumps are submersible pumps and are long cylindrical devices. At the very bottom of the pump is an electric motor which drives a whole series of small circular water pumps all stacked up one on top of the other and combined in a stainless steel housing. These pumps have to be powerful and, as any diver will tell you, every 10 metres of water depth the pressure increases by 14.7 pounds per square inch. To lift water 50 metres you need a pump that can pump water at 74 pounds per square inch, to put that into perspective the air pressure in your car tyre is only around 30 pounds per square inch. A bore 130 metres deep will typically need a pump capable of pumping water at 190 pounds per square inch (6 times the pressure in your car tyre) and will need a whopping 5.5 kilowatts of electrical power. These days a good quality pump for an average depth bore (30 to 50 metres) will cost around 8 million rupiah.

The submersible pump will also need a pipe to carry the water to the surface and a power cable to carry electricity to the pump.

Of course you don’t need to know all this, most of us live out our lives in happy oblivion. For the people of Europe a bit of edible equine hasn’t even been noticed has it? Horse, dog, rat there’s not much difference once it’s dead.

Copyright © Phil Wilson 2013
This article or any part of it cannot be copied or reproduced without permission from the copyright owner.

8 July 2018 Copyright © Mr Fixit,
Jl Bypass Ngurah Rai, Gg Penyu No 1, Sanur, Bali, Indonesia
Tel: +62-361-288-789