... sorry did not see your post earlier. And yes I was on this worst forum ever :-) ... I did not know that I could ask these questions as well here. Anyhow the well is done since yesterday and the yield seems to be very promising. Btw. - I have now 2 CSV's - the first took very long for delivery and Amazon gave me a refund but it subsequently arrived and the second CSV I ordered here on this site together with a cycle sensor.
Because all my water knowledge is pure theory from reading I welcome any type of help from people with experience. Here in the Philippines the experience is quite a challenge - if somebody ever touched a PVC water pipe here he immediately calls himself a plumber.
So let me summarize what I am gonna do now:
1. Install the submersible pump - a Goulds GS2515 with a 1.5 HP Franklin Motor plus Control Box.
2. My approach is to settle the pump at about 1.5 meter above the well screen at the bottom.
3. The well is 70 feet deep and the static water level is at about 15 feet.
4. I intend to acquire a Varem pressure tank (that's what they have here) of 20 liters (5.3 Gallons).
5. My thinking is to have the pressure tank at 55/75 and the CSV at 65. Because the filtration system after the pressure tank will consume about 15 PSI I will still get 50 in the house with a short low of 40 when the pressure tank is at its cut on point.
6. At last I will install a whole house water filtration system and then connect the house.
Interesting or better challenging will be to set the pressure switch and the CSV - I never did that of course and I am sure my "plumber" here did not do it yet either. Also interesting will be the discovery of new leaks :-) after the pressure got up from a max of 40 now to a max of 60 / 50 in the house with the new system. I intend to use PVC pipes everywhere (unless I get an advice to use PPR) - I will use 11/4 Inch from pump to pressure tank, 1 Inch from pressure tank to house and 3/4 inch to the individual consumers. Given your recommendation I will not install an additional check valve before the pressure tank - the Goulds has an internal check valve.
Of course I am happy with any advice :-) ... thanks anyhow.