We have two bore holes, and I can recount how they were installed and how they are used.
First bore holes are drilled not dug. If you dig then you will have a well, this will only go down to the first level of water which is essentially this or last seasons rain and more susceptible to contamination. A bore hole will be drilled to typically the second or third level of water (or more) depending on the quantity of water required and found. Also quality may have a bearing on which level is used. My deep bore hole (120M) produces about 200lts per minute, if I had a pump that big, and is at the third level. My shallower bore hole is 30M and produces about 17 -20lts a minute and is at the second level. The second level at the deep site is calculated to produce only 1000lts a day and as this was not sufficient the bore hole had to go deeper to find greater flow. Greater depth is not a guarantee of higher quantity, I have a friend who has a bore hole at 130M, third level and it only produces 9lts a minute.

It is important to line and seal the bore hole to avoid cross contamination between the layers. The bore holes here were drilled, lined with steel pipe for the deep and plastic for the shallow then a cement slurry was pored into the pipes followed by a wooden plug which was pushed down the pipe forcing the slurry out the bottom and up the outside of the pipe. The slurry came out at the top of the bore hole showing that the cement had sealed between the pipe and soil top to bottom. This as done when the drilling just reached the water layer. Once the cement had set (it was left for 2 weeks to harden) the drilling continued by drilling through wooden plug and a perforated pipe installed to allow water into the bore hole and the bore hole was then cleaned until clear water was produced.

Once you have the bore hole with water in it then thought can be given to the infrastructure to provide useable water coming out of a tap. At this stage the water should be tested to determine any treatment needed. Our deep bore hole has water with a high iron content so we have an iron filter with automatic back flush, the shallow bore hole, whilst producing hard water requires no treatment. We also have tourist lets so once a year the water is tested for bacterial contamination and this is sufficient for the regulations. (Testing for mineral content is only done once at the construction time and is not considered necessary after that). Filters are not fitted as a matter of course, only to resolve specific problems, for example our iron filter or perhaps a centrifugal filter for water with a high particle content.

When considering pumps it depends how deep the water level is. Our 120M bore hole has the water level at 40M from its own pressure and the pump is hung at 60M. If the water level is less than 9M from the surface then a surface pump can be used otherwise a submersible pump will be needed. The deep bore hole has standard ¾ inch plastic pipe with the pump hanging on a stainless steel multi-strand wire (yacht chandlers), as has the shallow bore hole. My friend with the 130M deep bore hole has galvanised iron pipe with barrel joints every 6M. this is because the water level is at 125M and this gives a pressure of 12.5 bar at the pump / pipe join and for this plastic was considered unsuitable. Pulling this pump out is no joke.

Our deep bore hole has a submersible pump feeding a 1000lt holding tank (800lts useable volume) which feeds a surface pump which feeds pressure vessel and then to the pipe infrastructure. After the pressure vessel the pipe work splits into two, the domestic water goes through the iron filter and the garden / farm water goes straight out. (Iron content is not harmful, just has a tendency to discolour the water if left standing)
The shallow bore hole has a submersible pump feeding a pressure vessel which then feeds the pipe work.
The deep bore hole infrastructure is in the corner of the cellar and the shallow bore hole infrastructure is in a manhole built around the top of the bore hole. Holding tanks and pressure vessels should be underground to keep the temperature down in the summer and to prevent freezing in the winter. The deep hole infrastructure is more complex due to 1, the deeper level, 2, the higher water usage at that site and 3, the need for the iron filter.
It is important that the water passes through the pressure vessel and that the pressure vessel is NOT teed off to the side. This is to ensure that the water in the pressure vessel is changes with use. German regs now forbid remote pressure vessels on drinking water supplies and insist on through flow vessels.

Pressure vessels should be large, not less that 100lts. This is to prevent short cycling of the pump. The vessel may be of the membrane type or just a plain tank. Both will need preloading with air pressure, however a plain tank will need topping up with air, probably monthly, but is much cheaper to buy. The membranes of membrane tanks seem to last about 2 – 5 years.
The decision regarding the fitting of a holding tank will depend upon the particular supply capability of the bore hole and the demand on the system. If the bore hole and submersible pump can supply the highest instant demand on the system then a holding tank will not be needed. When assessing this don’t forget that the output of a pump will decrease with increasing pressure so always use the pressure/flow rate charts supplied with pumps when assessing these. It is better to have the smallest holding tank consistent with meeting the supply demands to minimise the length of time water is stored.

I think this has briefly covered most of the points, if you have any questions ask and I will answer within the bounds of my experience. (By the way my surface pumps and pressure switches are Italian).
Peter

Now that ENEL have introduced their twin tariff, I'd recommend setting up the pump on a timer, and filling a cistern at off-peak rates. Even more so if your friend is on ENEL's non-resident tariff. I met someone a few years ago who had worked out it was cheaper to get water trucked in for his pool than fill it from his borehole (but I should add that the reliable water table is 450m down here.)

Also, I've seen a couple of tourists empty a 100 quintali cistern in 5 days, so I'd size the tank on the large side. If your friend is going to be marketing his place to northern europeans, it's best to work on the assumption that they're clueless about water usage.

He's planning on putting in a PV system so it would actually make sense to use electricity during the day. Ref the 2 pump v 1 pump, I was kinda getting there myself too - in that it didn't seem clear cut, so that helps. If it were me I would go for the holding tank solution (I just like the belt and braces approach, especially with paying guests) and the real gem is the gravity fed tank, it just hadn't ccurred to me (Thanks again Peter) - as it just so happens his house is at the bottom of a substantial slope, he has major earth moving equipment running around and the first piece of the slope has just been cleared apart from some young walnut trees.

ASIDE - Contadino, we currently have 3 tariffs for different times of the day and 3 tariffs based on annual usage - yes that's 9 possible tariffs and it is possible to use all of them in a day (theoretically)and we have an up and running PV system for which no-one can state how much we will actually be paid per Kw for the electricity we have sent ENEL!!!

My holding tank (on the deep bore hole, the shallow bore hole is single pump = no holding tank) has no cleaning treatment such as UV or other. At 800lts it is less than one days usage and the pressure vessel is through flow type. (The farm animals account for most of the usage). The water coming from the bore hole is clean and with such short term storage treatment has never been found to be necessary. Our water however has a high iron content so we have an iron filter to remove the iron content of the water that is for domestic use as a high iron content can make the water brownish if stored for a bit. (Health wise it has no effect as it passes straight through.....so I am told).
Our pressure vessel is a 120ltr galv. steel hot water tank, redundant for its designed usage and recycled into our water infrastructure. As it is without a diaphragm it requires topping up with air about once a month.
Peter

Has anyone tried/found a good solar/wind powered pump to trickle feed a holding tank or should I just consider making up my own 'kit'?