How long can I store water in a rainwater cistern?

You are watering quite a lot or have soil that doesn’t retain water. I haven’t looked at the water meter this year yet, but with our approximately 250m² of pure garden area (lawn/hedge/beds), we have never needed more than 30m³ per year in the last 4 years. The problem is, the more you water, the less the roots develop and the more you have to water again.

Hello;

Of course, it does make a difference whether I use rainwater from the cistern or drinking water. On average, one uses 15-20L/sqm per week (summer months), so with a 300sqm garden, that’s 6000L of water per week. The filters are planned from the start and don’t cost a fortune.

Yes, it makes a difference, with rainwater you need the filters in your pipes, and with drinking water you don’t. They aren’t that cheap either. They cost you 30-50 euros per year. I can also safely fill my children’s paddling pool with drinking water; with possibly stagnant rainwater, I’d be a bit cautious. My son also likes to try to drink the pool water.

Regarding the environment, yes, it’s true, at first glance it seems a bit contradictory to first treat water (which isn’t environmentally harmful though) and then let it infiltrate into the garden. But a cistern doesn’t just fall from the sky or grow on a tree! The production of PE (plastic cistern) is quite a mess, and if you look at the CO2 footprint of concrete (cement production), you’d want to avoid a concrete cistern too. And the electricity your cistern pump uses isn’t negligible either; those things have 0.5–1 kW. If it runs 1–1.5 hours every day, that’s not an insignificant energy consumption. You end up with roughly 1 kWh per m3. The water treatment by your municipal utilities is probably much more efficient.

Best regards,

Andreas

You’re definitely watering a lot or you have soil that doesn’t retain moisture.

Both are the case. As I said, the garden is newly created, and we will probably be able to reduce watering somewhat in the long term. For now, the plants in the bed first have to root properly and the lawn should become really dense. Saving water is not a priority yet.

Best regards,

Andreas

But a cistern doesn't just fall from the sky or grow on a tree! The production of PE (plastic cistern) is also quite a mess, and if you look at the CO2 footprint of concrete (cement production), you should also stay away from a concrete cistern.
And the electricity your cistern pump uses is no small matter either, those things have 0.5-1 kW. If they run 1-1.5 hours every day, that's not a small electricity consumption. That easily adds up to 1 kWh / m3. The water treatment by your municipal utilities is probably much more efficient.

Best regards,

Andreas

Yes, that's true, of course they don't fall from the sky and of course the production shouldn't be forgotten. But these are one-time costs and negligible in the long term.
You can still fill a paddling pool with drinking water because most houses have 2 tap points; if the cistern runs empty, you can still water with drinking water... at least that's how it is with us.
In many communities, a cistern is now mandatory, so there's no question about it.
I can't say anything about consumption because we are still building.

The filters are also not changed every year; it's only for the garden. Usually, it's enough to clean it by hand, as it's mostly just a mesh. If used for toilet flushing and/or washing machine, different filters are installed.

Both are the case. As I said, the garden is newly laid out, and we will probably be able to reduce watering somewhat in the long term. Currently, the plants in the bed first have to root properly and the lawn should become really dense. Saving water is not yet the order of the day.

Best regards,

Andreas

That will definitely be less. In the first year we also used the most so far. In the following years, it was between 15 and 20 m³. However, this year there has already been a ban in some towns on watering the garden with drinking water. But this apparently was due to technical problems (e.g. lack of line pressure between 5 and 9 p.m.) rather than water shortage. Having your own water reservoir is certainly an advantage.

This topic has already come up once. Here is the link

And if an expansion vessel is used, the pump does not have to switch constantly between day/night, so you can save electricity as well