Cistern overflow too low for natural overflow

Hello,

After searching the internet for a long time, I believe I have not yet looked in the right place.

We are currently building a new house and want to use a cistern to water the garden later. However, there are a few parameters to consider.

1. Excess rainwater must not go into the wastewater system
2. Excess rainwater must be discharged over the street
3. The cistern will be located below street level

From this, it follows that we need a system to transport the overflowing water to the higher street level.

I have already looked at various pump systems for this. However, from an ecological perspective, the cistern makes little sense if the advantage is negated by the use of a pump. Also, so far I have mostly only seen submersible pumps, which would not remove the dirt on the surface water of the cistern.

Hoping that we are not the first to want to use a cistern under such conditions, I hope for good new ideas here.

Kind regards Florian

Normally, it is the case that you are not allowed/should not direct water (surface water) from private property onto the public street. If everyone did that, the drainage system designed for the street would no longer work! Point 1 is correct Point 2 I see differently Point 3 will "almost" always be that a cistern is located below street level

Exciting topic, I dealt with a similar issue today as well. We are not allowed to let the rainwater infiltrate at a single point and do not have a connection to a pipe for this. We are required to collect the water with a cistern and let it infiltrate through soakaways. This might also be an approach for you.

No possibility to install the cistern so that the overflow is above ground level? Otherwise, I only see a pump as a solution or infiltration on the property. You have a pump anyway to draw water. I can imagine a sensor and a multi-way valve. If the water level is above the specified level, the valve automatically switches, the pump starts, and lowers the water level. Are you really allowed to drain into public land or the sewer??? It would be great if that were allowed. In many areas, there is not enough water in the sewer system and it has to be flushed with fresh water.

There are also flat tanks that are not installed as deep and thus allow for a relatively high outlet. The question with the pump is whether it can even manage to remove the water during a heavy downpour.

What kind of surfaces are we talking about that are supposed to drain into the cistern? How large should it be? If you want an automatic irrigation system, you need a pump with sufficient volume and pressure anyway. A pump with e.g. 6m 3 / h can move enough water... large heights probably cannot be overcome.