Looking for experiences with garden water well pumps

we had a 21m deep garden water well, it was operated with a suction pump, unfortunately the water column always dropped very far, so it took forever until water came.

Your problem is that suction pumps can pump a maximum height of 10m. More is physically not possible. So the classic solution is to buy a submersible pump. Decent models cost around/from €500. Plus a pressure switch. A well driller once told me that he charges about €100 per meter + pump. Pipe/filter pipe is of course included in that.

So ours wants 70m per meter plus pump. The offer includes a Grundfos SQ 2 55, which is available online for €650 plus €100 pressure switch and the €250 installation, then I am at €1000 instead of €1700 for the same pump

Attention, the Grundfos SQ 255 has only 2,000 liters/hour flow rate. Not suitable for automatic irrigation. For less money, there is the deep well pump Tipp AJ 4 Plus 100/57 AUT with significantly better performance data (delivery height and especially flow rate). I also know of two installations where this pump runs without problems. Moreover, it can be replaced easily and cheaply for the price.

the pump you found is also good in terms of performance data. However, it has almost double the power consumption (2.2kw). If you want to irrigate automatically, this will be noticeable since the pump runs for several hours per week.

Mercedes is more like Wilo ;)

Suction pump probably not suitable for 21 meters height difference. And probably also rather "weak". For example, for automatic irrigation you need sufficient pressure and flow.

My cistern is only 1 meter deeper. I'm surprised anyway that the well at 21 meters depth worked with a suction pump.

Well, 21m deep doesn't mean that the pump is sucking from 21m depth, the water in the well was at about 8m or so.... It still worked optimally. We had attached a connection and always let tap water run in for 1 minute first, then it would start sucking immediately. But that shouldn't be the intention of the inventor, and if you want an automatic irrigation system, it's simply not possible...