Hello everyone,
We are currently working on building our single-family house. The building application has been submitted, and we promptly received the first letter from the building authority stating:
Rainwater must generally be infiltrated or directed into a nearby open water body, as long as this is possible without excessive effort and damage (§ 48 b Abs. 3 WG-BW).
After a phone consultation with the building authority, we were told that rainwater is not allowed to be discharged into the sewer system due to water protection zone III. The proposed solution (if you can call it that, as they basically said “there’s no way around it”) is a cistern. Permeable paving was also mentioned for the driveway, although we’re not sure what that is for. There is no water body nearby, by the way.
We had actually considered a cistern for watering the garden but excluded it due to the cost. Now we are being forced to install one despite the financial strain, so I have a question for you.
There seem to be countless types of cisterns (according to Google). Can you tell me which type would suit our purpose and where it’s most important not to cut corners?
Kind regards
We are currently working on building our single-family house. The building application has been submitted, and we promptly received the first letter from the building authority stating:
Rainwater must generally be infiltrated or directed into a nearby open water body, as long as this is possible without excessive effort and damage (§ 48 b Abs. 3 WG-BW).
After a phone consultation with the building authority, we were told that rainwater is not allowed to be discharged into the sewer system due to water protection zone III. The proposed solution (if you can call it that, as they basically said “there’s no way around it”) is a cistern. Permeable paving was also mentioned for the driveway, although we’re not sure what that is for. There is no water body nearby, by the way.
We had actually considered a cistern for watering the garden but excluded it due to the cost. Now we are being forced to install one despite the financial strain, so I have a question for you.
There seem to be countless types of cisterns (according to Google). Can you tell me which type would suit our purpose and where it’s most important not to cut corners?
Kind regards
WilderSueden schrieb:
The house is about 9x10m (30x33 feet) without the extension. So, not huge, but not very small either. I already thought that, but next to the huge cistern it really looks like a tiny house! 😀
WilderSueden schrieb:
Definitely find out. Ask the neighbors or get the soil survey done earlier. If the cistern is unstable, I wouldn’t wait until the last minute to decide on the waterproof concrete basement (also known as a “white tank”). Hmm, we were always told to do the soil survey only once you are 100% certain where the house will be located. Now that I say it out loud again, I can hardly believe the house would shift after submitting the building permit / planning permission 😕. I’ll start looking for a soil surveyor... Thanks for the warning!
W
WilderSueden17 Mar 2022 19:08Either you have a building site that is relatively level. In that case, it doesn’t matter if you move the house by 3 meters (10 feet) or make it 1 meter (3 feet) wider. Then you can also do the soil survey early.
Or you have a building site where every meter is completely different. Then, even with boreholes at the corners, you can still get surprises when the excavation is done 😉
Or you have a building site where every meter is completely different. Then, even with boreholes at the corners, you can still get surprises when the excavation is done 😉
nokapito schrieb:
We need to submit a "wastewater calculation," I'm very curious to see how he'll handle it...
Usually, this takes about three hours for the architect.
All sealed surfaces are added together to calculate the amount of rainfall that needs to be drained, and based on that, the size of the infiltration trench (soakaway) is determined. This is then marked on the property (for example, in the garden) and submitted as a plan along with the calculated values.
By the way: Some use or calculate with basket soakaways (expensive), others with common pipe soakaways (more affordable).
At the time, we planned with basket soakaways, but shortly before construction, it turned out they were significantly more expensive and not available. We quickly switched to the cheaper pipe soakaways and even hired a different architect who recalculated it for just 200 EUR. Then off to the authorities... although this is mostly a "formal procedure," and practically no one checks the details.
nokapito schrieb:
What does that mean? A meter for garden water?
Depending on the municipality, you can simply install or register a water meter on the outdoor faucet (for garden use) and then you don’t pay sewage fees on the amount of water used. Some places have the water supplier seal the meter, while in others, you can just register your own meter and that’s it. They cost a small amount but pay off relatively quickly, since the costs without the sewage portion are significantly lower for the water used.
TmMike_2 schrieb:
That would be extremely cheap! For a deep well pump? Or just a suction hose? I assume you mean "just a suction hose" 🙂
G
Gartenfreund18 Mar 2022 07:04We buried a plastic cistern here. It cost 750 euros a few years ago.
The excavation and everything else was done as a DIY project.
A soakaway was not an option.
So I chose the simplest solution. When the water reaches a certain level, excess water is pumped into the garden where it can then infiltrate at the surface.
Regarding size: There are various websites where you can calculate the required cistern volume. Unfortunately, they sometimes suggest different sizes even with the same input values.
I would not use concrete manhole rings. They are quite heavy, even at small diameters, and therefore likely require special clamps for transport and installation. In addition, an excavator or similar equipment may be needed to install them.
The excavation and everything else was done as a DIY project.
A soakaway was not an option.
- I did not want to spend 100 euros just to inquire whether such a system is allowed.
- There was also the question of how it would look after several years. Whether a lot of dirt would accumulate inside, causing the soakaway to stop working properly.
- I would have had to deal with roots from trees and shrubs to install this soakaway.
So I chose the simplest solution. When the water reaches a certain level, excess water is pumped into the garden where it can then infiltrate at the surface.
Regarding size: There are various websites where you can calculate the required cistern volume. Unfortunately, they sometimes suggest different sizes even with the same input values.
I would not use concrete manhole rings. They are quite heavy, even at small diameters, and therefore likely require special clamps for transport and installation. In addition, an excavator or similar equipment may be needed to install them.
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