Hello everyone,
I’m currently unsure whether we need a backflow prevention device for our construction project or not. Our architect was only somewhat helpful and said that we “actually” don’t need one, but if we wanted to be on the safe side, we could of course have one installed.
Here are the key details:
The plot is connected to a separate sewer system.
We are building without a basement and have no shower on the ground floor, meaning the lowest wastewater outlet in the house should be the toilet on the ground floor.
The plot is located on a slightly sloping street (downhill from top to bottom according to the plan). Attached are the city’s drainage plan and a cross-section of the planned house, both with elevation details.
The city’s drainage regulations contain no information regarding the backflow level, which I understand to mean that the street elevation corresponds to the backflow level (please correct me if this is wrong).
Based on this, I understand the situation as follows:
- The nearest manhole cover uphill from our plot is at 163.52m NHN (according to the plan provided by our surveyor for the building permit, it is at 163.48m NHN). The nearest manhole cover downhill is at 162.23m NHN.
- The top of the floor slab is at 163.30m NHN, plus 0.18m (7 inches) floor build-up, plus about 0.20m (8 inches) to the toilet outlet = 163.68m NHN.
As a non-expert, I would conclude that a backflow prevention device is not necessary since the lowest outlet is 16 (or rather 20) centimeters (6 or 8 inches) higher than the nearest uphill manhole cover. Is that correct?
However, I wonder why the architect said that I could “install a backflow prevention device to be on the safe side.” Of course, I could just ask him, but I wanted to inform myself here first to better understand his answer.
Thank you all in advance and have a nice second Advent!
I’m currently unsure whether we need a backflow prevention device for our construction project or not. Our architect was only somewhat helpful and said that we “actually” don’t need one, but if we wanted to be on the safe side, we could of course have one installed.
Here are the key details:
The plot is connected to a separate sewer system.
We are building without a basement and have no shower on the ground floor, meaning the lowest wastewater outlet in the house should be the toilet on the ground floor.
The plot is located on a slightly sloping street (downhill from top to bottom according to the plan). Attached are the city’s drainage plan and a cross-section of the planned house, both with elevation details.
The city’s drainage regulations contain no information regarding the backflow level, which I understand to mean that the street elevation corresponds to the backflow level (please correct me if this is wrong).
Based on this, I understand the situation as follows:
- The nearest manhole cover uphill from our plot is at 163.52m NHN (according to the plan provided by our surveyor for the building permit, it is at 163.48m NHN). The nearest manhole cover downhill is at 162.23m NHN.
- The top of the floor slab is at 163.30m NHN, plus 0.18m (7 inches) floor build-up, plus about 0.20m (8 inches) to the toilet outlet = 163.68m NHN.
As a non-expert, I would conclude that a backflow prevention device is not necessary since the lowest outlet is 16 (or rather 20) centimeters (6 or 8 inches) higher than the nearest uphill manhole cover. Is that correct?
However, I wonder why the architect said that I could “install a backflow prevention device to be on the safe side.” Of course, I could just ask him, but I wanted to inform myself here first to better understand his answer.
Thank you all in advance and have a nice second Advent!
B
BananaJoe7 Dec 2020 12:12Nida35a schrieb:
When heavy rain comes, and water pushes up from above and below, the shaft is the first to flood, and you realize that no inspection or cleaning has been done for 5 years because it’s too narrow and nobody can access it. So is it better not to install a backflow prevention device if you don’t have a basement? 🙄 Or what do you suggest?
At our place, there is no basement with the bungalow. The finished floor level is 20cm (8 inches) above the finished ground level. There are stone edges around the house, and all slopes direct water away from the house. During heavy rain, it looks like the water flows past and away from the building.
On the path, the inspection covers for the sewage system are open. We only experience flooding if water stands 1m (3 feet) all around. In that case, we open all the doors. By then, all neighbors with basements have already had flooding.
On the path, the inspection covers for the sewage system are open. We only experience flooding if water stands 1m (3 feet) all around. In that case, we open all the doors. By then, all neighbors with basements have already had flooding.
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