Hello everyone,
We are close to submitting our building permit / planning permission, and our builder claims that we are required to plan and install a backflow prevention system.
We understand this in principle. However, what really isn’t clear to us is why we are not allowed to install a backwater valve for sewage and are allegedly required to install a lifting station (sump pump system).
Here is the situation:
The plot is completely flat, and rainwater is not allowed to be discharged into the sewer system anywhere in the development; it must drain into an infiltration pit. Our ground floor is located approximately 30cm (12 inches) below the last backflow level in the sewer. The property / development is situated on top of a hill, so no water is flowing downhill toward it; in fact, water drains away quickly.
This means that for a rare event that might occur once every five years, when the sewer cannot handle the rainwater, we are supposed to install a lifting station.
In our opinion, a backwater valve would clearly be sufficient in this case, not a lifting station. The lifting station serves a different purpose for us. Furthermore, this system is not allowed to be installed outside the building, so we would have to have a flap and the system under the slab in the utility room.
The whole setup is estimated to cost about 7,000 euros (around $7,700) without any excavation work.
Are we being too simplistic, or is the builder correct?
By the way, for insurance purposes, a backflow prevention device is important. A flap valve alone should be enough and certainly achieve the same effect.
Thank you for your opinions.
We are close to submitting our building permit / planning permission, and our builder claims that we are required to plan and install a backflow prevention system.
We understand this in principle. However, what really isn’t clear to us is why we are not allowed to install a backwater valve for sewage and are allegedly required to install a lifting station (sump pump system).
Here is the situation:
The plot is completely flat, and rainwater is not allowed to be discharged into the sewer system anywhere in the development; it must drain into an infiltration pit. Our ground floor is located approximately 30cm (12 inches) below the last backflow level in the sewer. The property / development is situated on top of a hill, so no water is flowing downhill toward it; in fact, water drains away quickly.
This means that for a rare event that might occur once every five years, when the sewer cannot handle the rainwater, we are supposed to install a lifting station.
In our opinion, a backwater valve would clearly be sufficient in this case, not a lifting station. The lifting station serves a different purpose for us. Furthermore, this system is not allowed to be installed outside the building, so we would have to have a flap and the system under the slab in the utility room.
The whole setup is estimated to cost about 7,000 euros (around $7,700) without any excavation work.
Are we being too simplistic, or is the builder correct?
By the way, for insurance purposes, a backflow prevention device is important. A flap valve alone should be enough and certainly achieve the same effect.
Thank you for your opinions.
Then it can only be due to the zoning plan, since a 30cm (12 inches) height difference does not make a difference. The "sewer pipe" is several meters below the road, so 30cm (12 inches) doesn’t matter. The only explanation left is the zoning plan that requires it. Otherwise, it’s nonsense. Maybe you should ask the building authority or check with neighbors if they have a similar setup.
You are building with a developer, so house and land from one source? If you already have a construction company, try asking another company as well.
You are building with a developer, so house and land from one source? If you already have a construction company, try asking another company as well.
Hi,
do you have a drawing of the planned drainage layout?
Something doesn’t add up in your description, or I’m not understanding it...
You mention once that "rainwater must infiltrate into the ground" and elsewhere that "the sewer could overflow during rain"?
In your first post, your ground floor is 30cm (12 inches) below street level, but in your second post, the street is 30cm (12 inches) below the house.
So which one is it?
Let’s assume the worst case: the ground floor is 30cm (12 inches) below the backflow level.
The backflow level is usually the manhole cover, which corresponds to the street surface level.
The actual sewer pipe will be about 1.5–3m (5–10 feet) deeper, so if you don’t have a basement and your ground floor is only 30cm (12 inches) below street level, you definitely don’t have a slope problem reaching the sewer with your wastewater. Since all traps inside the house should be well above 30cm (12 inches), a backwater valve is actually unnecessary. Before wastewater can back up through your sink or toilet, the street-level manhole will already be overflowing and water will be pressing against your front door. At that point, even a sewage lift station won’t help you...
Best regards,
Andreas
do you have a drawing of the planned drainage layout?
Something doesn’t add up in your description, or I’m not understanding it...
You mention once that "rainwater must infiltrate into the ground" and elsewhere that "the sewer could overflow during rain"?
In your first post, your ground floor is 30cm (12 inches) below street level, but in your second post, the street is 30cm (12 inches) below the house.
So which one is it?
Let’s assume the worst case: the ground floor is 30cm (12 inches) below the backflow level.
The backflow level is usually the manhole cover, which corresponds to the street surface level.
The actual sewer pipe will be about 1.5–3m (5–10 feet) deeper, so if you don’t have a basement and your ground floor is only 30cm (12 inches) below street level, you definitely don’t have a slope problem reaching the sewer with your wastewater. Since all traps inside the house should be well above 30cm (12 inches), a backwater valve is actually unnecessary. Before wastewater can back up through your sink or toilet, the street-level manhole will already be overflowing and water will be pressing against your front door. At that point, even a sewage lift station won’t help you...
Best regards,
Andreas
Or could it be that Payday is right with his assumption, and they want you to install a rainwater infiltration tank with an overflow? One that actually doesn’t require a pumping station given the conditions? But even for a large tank with a powerful pumping system, 7,000 € is expensive.
You’re building with a ground floor and an upper floor, right? And no basement? And your ground floor is 30cm (12 inches) below street level?
The problem with this setup, if I understand correctly, is that your ground floor is below the backflow level. So, if the drain backs up, wastewater will be pushed into the pipes on your ground floor. For this reason, an electric backwater valve is definitely necessary, since you probably have a toilet on the ground floor as well.
A lifting station becomes unavoidable if the bottom of the drain trap is still above your ground floor, though I can’t really imagine that in your case. There is another scenario as well: if you only have a toilet on the ground floor, then you will need a lifting station or a backwater valve combined with a pump, which alone costs around 2,500€. This is because each dwelling must ensure that, in the event of backflow—when the valve is closed—wastewater containing fecal matter can still be discharged, and this is only possible with a pump.
The problem with this setup, if I understand correctly, is that your ground floor is below the backflow level. So, if the drain backs up, wastewater will be pushed into the pipes on your ground floor. For this reason, an electric backwater valve is definitely necessary, since you probably have a toilet on the ground floor as well.
A lifting station becomes unavoidable if the bottom of the drain trap is still above your ground floor, though I can’t really imagine that in your case. There is another scenario as well: if you only have a toilet on the ground floor, then you will need a lifting station or a backwater valve combined with a pump, which alone costs around 2,500€. This is because each dwelling must ensure that, in the event of backflow—when the valve is closed—wastewater containing fecal matter can still be discharged, and this is only possible with a pump.
P
Polle 196720 May 2016 12:42Do you have the option to raise the single-family house higher?
Uwe82 schrieb:
The problem with this setup, if I understand correctly, is that your ground floor is below the backwater level. So if the drain overflows, wastewater will be pushed back into the pipes on the ground floor. For this reason, you definitely need an electric backflow valve, especially since you probably have a toilet on the ground floor as well.
Even if the ground floor is 30 cm (12 inches) below street level, the top edge of the toilet is still 15–20 cm (6–8 inches) above the street and therefore above the backwater level.
Nothing can come up through the toilet unless you have a local black hole that reverses all the laws of gravity in your bathroom….
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