ᐅ How long can rainwater be stored in a rainwater harvesting tank?

You’re definitely watering a lot or have soil that doesn’t retain moisture.
I haven’t checked the water meter this year yet, but for our approximately 250m² (2700 sq ft) of pure garden area (lawn/hedges/flower beds), we have never needed more than 30m³ (almost 8,000 gallons) 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;

niri09 schrieb:
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 for 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 does make a difference. With rainwater, you need filters in your pipes, but not with drinking water. They’re not exactly cheap either. They cost you about 30-50 Euros per year. I can safely fill my children’s paddling pool with drinking water, but I’d be a bit cautious with possibly stagnant rainwater. My son also likes to try drinking from the pool.

Regarding the environment, yes, at first glance it seems a bit contradictory to treat water (which is not really harmful to the environment) only to then let it soak into the garden. But a cistern doesn’t just appear out of nowhere or grow on a tree! Manufacturing PE (plastic cisterns) is quite a messy process, and if you look at the CO2 footprint of concrete (cement production), you might want to avoid a concrete cistern as well.

Also, the electricity consumption of your cistern pump is not negligible either; these pumps consume 0.5-1 kW. If they run for 1-1.5 hours daily, that’s quite a bit of power usage. That quickly adds up to about 1 kWh per cubic meter. The water treatment by your municipal utility is probably much more efficient.

Best regards,

Andreas

Musketier schrieb:
You must be watering quite a lot there, or you have soil that doesn’t retain water.

Both are true. As I said, the garden is newly established, so we will probably be able to reduce watering a bit in the long term. For now, the plants in the flower bed need to establish strong roots, and the lawn needs to grow in thick. Saving water is not a priority at this stage.

Best regards,

Andreas

andimann schrieb:



But a cistern doesn’t just fall from the sky or grow on a tree! Manufacturing a PE (plastic cistern) is quite a messy process, and if you look at the CO2 footprint of concrete (cement production), you’d probably want to avoid a concrete cistern as well.
Also, the electricity consumption of your cistern pump isn’t insignificant; these units typically use 0.5–1 kW. If they run for 1–1.5 hours daily, that’s a considerable amount of power. That quickly adds up to about 1 kWh per cubic meter of water. The water treatment from your municipal supplier is likely to be much more efficient.

Best regards,
Andreas

Yes, that’s true, of course they don’t just appear out of nowhere and the production should not be forgotten. However, these are one-time costs and negligible in the long term.
You can still fill a paddling pool with drinking water, since most houses have two water connections; if the cistern runs empty, you can still water the garden with drinking water—at least that’s the case where we live.
In many municipalities, having a cistern is now mandatory, so there’s no question about it.
Regarding consumption, I can’t say yet since we are still building.

The filters are not changed every year either, since this is mainly for the garden. Usually, cleaning them by hand is sufficient, as they are often just some kind of mesh. If the water is used for toilet flushing and/or washing machines, different filters are installed.

andimann schrieb:
Both apply. As mentioned, the garden is newly established, so we will probably be able to reduce watering somewhat in the long term. At the moment, the plants in the flower bed still need to establish strong roots, and the lawn needs to become dense. Saving water is not a priority yet.

Best regards,

Andreas

It 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 (530 to 700 cubic feet).

However, this year some towns have already banned watering gardens with drinking water. This was apparently due to technical problems (e.g., insufficient water pressure between 5 and 9 pm), rather than an actual water shortage. Having a private water reservoir is obviously an advantage in such cases.

This topic has come up before. Here is the link
https://www.hausbau-forum.de/threads/dimension-Zisterne.16292/?_params=Array

And if an expansion tank is used, the pump does not have to constantly switch between day and night settings, which can also save electricity.