Hello,
I am currently considering the sizing of the rainwater cistern and the connected infiltration shaft. According to calculations, a cistern with a capacity of just over 3000 liters (around 790 gallons) should be sufficient (rainwater from the roof). However, I would prefer to have a larger buffer and am thinking of something in the range of 4,000 to 5,000 liters (1,050 to 1,320 gallons). Now, my question is how to plan the subsequent infiltration shaft?
There are plastic shafts available with a capacity of 140 liters (37 gallons) for about 160€, the next size up is 500 liters (130 gallons) for around 350€, and another option is 900 liters (240 gallons) at about 430€. Does anyone have any ideas or experience using a similar combination? Introducing the water into the stormwater/sewage system should preferably be avoided.
Thanks!
I am currently considering the sizing of the rainwater cistern and the connected infiltration shaft. According to calculations, a cistern with a capacity of just over 3000 liters (around 790 gallons) should be sufficient (rainwater from the roof). However, I would prefer to have a larger buffer and am thinking of something in the range of 4,000 to 5,000 liters (1,050 to 1,320 gallons). Now, my question is how to plan the subsequent infiltration shaft?
There are plastic shafts available with a capacity of 140 liters (37 gallons) for about 160€, the next size up is 500 liters (130 gallons) for around 350€, and another option is 900 liters (240 gallons) at about 430€. Does anyone have any ideas or experience using a similar combination? Introducing the water into the stormwater/sewage system should preferably be avoided.
Thanks!
It depends on the boundary conditions. Is on-site infiltration required, or are you allowed to discharge the water elsewhere? What does the building permit / planning permission specify?
The extreme case would be infiltration on your own property with a proof obligation to the water authority. In that case, you need a calculated verification that during a heavy rainfall event and with a full cistern, the water can still be absorbed based on the infiltration capacity demonstrated by a geotechnical report.
If no one insists on this, you can simply dig a hole, pour water in, and measure how long it takes to infiltrate, repeating the test several times before taking measurements. Then you can calculate the maximum amount of water from your roof in one hour and size the infiltration shaft accordingly.
The extreme case would be infiltration on your own property with a proof obligation to the water authority. In that case, you need a calculated verification that during a heavy rainfall event and with a full cistern, the water can still be absorbed based on the infiltration capacity demonstrated by a geotechnical report.
If no one insists on this, you can simply dig a hole, pour water in, and measure how long it takes to infiltrate, repeating the test several times before taking measurements. Then you can calculate the maximum amount of water from your roof in one hour and size the infiltration shaft accordingly.
Soil survey indicates that infiltration from the overflow of a cistern is possible and can be implemented using a vertical structure (soakaway shaft).
The development plan states that stormwater is collected within the building area and drained (this probably refers to the stormwater sewer), or infiltrated on the property itself. This is addressed only in this one sentence.
The building permit is still pending. The application mentions a cistern and a soakaway shaft.
The development plan states that stormwater is collected within the building area and drained (this probably refers to the stormwater sewer), or infiltrated on the property itself. This is addressed only in this one sentence.
The building permit is still pending. The application mentions a cistern and a soakaway shaft.
H
hampshire16 Apr 2019 18:25On our property, we installed an infiltration trench corresponding to the calculated sealed surface area. On the way there, the cistern is simply used as an intermediate storage. It will just be approved. Overflow is therefore not a problem and goes into the infiltration trench.
Hello,
I have a question I need to clarify:
If the overflow from a cistern drains into the stormwater sewer, is it allowed to connect directly, or is a manhole required in between? Or is a manhole only necessary with the combined sewer? Is such a chamber mandatory by law, or what regulations determine this?
Thank you!
I have a question I need to clarify:
If the overflow from a cistern drains into the stormwater sewer, is it allowed to connect directly, or is a manhole required in between? Or is a manhole only necessary with the combined sewer? Is such a chamber mandatory by law, or what regulations determine this?
Thank you!
I am not familiar with the legal requirements. But even if a connection with a natural slope were possible, I would optionally consider installing a downstream inspection chamber (possibly just a plastic DN 400 (16 inches) if no traffic load is required) with a backflow prevention device.
In the event of backflow, the question remains where to direct the excess rainwater. So it might be necessary to also plan an emergency overflow, for example, into the existing infiltration system.
In the event of backflow, the question remains where to direct the excess rainwater. So it might be necessary to also plan an emergency overflow, for example, into the existing infiltration system.
Similar topics