Is a cistern economically viable through pumping?

The water from the well is often very alkaline or rich in iron. Not all plants tolerate that well. Rainwater is perfect for plants. But yes, economically it is usually not worthwhile.

When it comes to irrigation, the question is always what you want. Anyone who waters their English lawn twice a week with 20l/sqm each time will not be happy with a normal cistern. Most people don't need that, and after three weeks of dryness, watering 250sqm once also works with a 5cbm cistern. There is even some left for the vegetable garden. In addition to the well, of course, this is probably not economical.

When it comes to irrigation, the question is always what you want. Anyone who waters their English lawn twice a week with 20l/sqm each time will not be happy with a normal cistern. Most people don't need that, and after 3 weeks of drought, watering 250sqm once is also possible with a 5cbm cistern. There's even some left for the vegetable garden. In addition to the well, this is of course probably not economical.

Now not everyone has just 250 sqm. After 3 weeks of drought watering once you can forget about it, by then most of the plants are dead or at least ruined for the season. There are not only lawns or vegetable gardens, but also perennials and hedges. And you don’t want to sit in a dry garden in summer; at least it should be a green area (doesn’t have to be an English lawn) with many flowering plants.

3 weeks of drought does not exclude green and colorful. There are enough plants, especially among perennials, that cope excellently with drought. Meadows and herb lawns handle drought quite well and recover extremely quickly after rain. Trees and shrubs can root deeply, then 3 weeks without rain are enough. Even in the Brandenburg sand, there are said to be plants in the wild that manage with what nature offers and are nice to look at ;)

And don't underestimate how much area there is to water in the end. Let's calculate a house with 10x10m plus eaves strip, garage, garden shed, terrace, driveway, paths,... quickly adds up to 300 sqm and is in the right size range with today's typical plots.

Here 270m² of lawn that stays green all year round like from a picture book, plus hedges, lots of roses, vegetable bed. I like to water generously, yet I have never emptied the cistern. So I wish everyone their own well, but the doomsday scenarios that after three weeks of summer everything is dead, I could not observe here. On the contrary, I watered like crazy and with the next thunderstorm the place was full again. So please don’t make up scare stories. And by the way: groundwater can also sink and die during drought. So even if my cistern should actually be empty someday, you have to consider how deep the well goes. Rainwater can also be used not only excellently for irrigation but also, for example, to wash photovoltaic systems (of course not in the sun) because it does not cause lime stains.

I would like to point out that the water from the cistern has to be pumped out with a pressure pump at 30-40 cents/kWh, while the garden water shoots out by itself from the tap at 3-5 bar. Such a pump costs 200, 300 EUR, does not last forever, you have to replace filters, etc. 2, 3 hours of sprinkling the lawn quickly come to 1 kWh. I mean, even operating a cistern is not free.

A cistern only pays off after many years. In winter it is always full, so an additional infiltration is needed, which means more costs.

And in summer... What are 5,000 liters in the height of summer? It even evaporates into the air before it reaches the lawn.