Drainage from retention cistern into higher RW channel

  • Erstellt am 2022-11-02 20:03:24

mutzbratem

2022-11-02 20:03:24
  • #1
Hello forum members :) I am new here in the forum and have an interesting question right away. We are currently building a single-family house near Chemnitz and have to prove 3 cubic meters of retention volume per 100 sqm of sealed surface and discharge 1 l/s. In our case, that means 6000 l retention volume + 4000 l for own use = 10000 l monolithic concrete cistern (drive-overable under the driveway).

Since the street is 50 cm above the property level and I want to drain freely sloping into the cistern, it has to be relatively deep in the ground.

Problem: Now the retention throttle is located below the RW sewer of the street, so I need a lift pump to be able to drain. The overflow is just above the sewer - here there are no problems.

The cistern builder said we should build a lift shaft next to the cistern, where the throttle can discharge at 1 l/s and put a submersible pump with a float switch inside, which then pumps the water into the sewer - honestly ... that’s nonsense. Then the pump keeps switching on, pumps a little with a flow rate > 1 l/s into the sewer and switches off again ... on again ... off again and so on.

My idea was to install a submersible pump with a throttle orifice directly in the cistern, which drains via a hose into the sewer. I would mount the pump at a height between retention volume and storage volume. I don’t need an expensive retention throttle for this, no hole has to be made in the wall, nothing can leak and so on ... only advantages in my opinion.

What do you think about that? Would the wastewater association have any objections? How would or have you solved such a problem? I hope I have expressed myself clearly and someone can chime in here. :)

Kind regards from the Ore Mountains
 

Gartenfreund

2022-11-03 02:34:41
  • #2
Why don't you use the water 100% for your garden?

Is the soil not suitable for that?

I did it like this here.

When the cistern reaches a certain fill level, a wastewater pump (with float switch) activates and pumps the excess water into an above-ground slotted HT pipe which then distributes the water over several meters in the garden.

This way, I could avoid connecting to the sewer. And I no longer have to pay any fees for it.
 

mutzbratem

2022-11-03 05:55:08
  • #3
Basically a good idea. But we have many requirements in the development plan from the wastewater association. We are building relatively high up on a mountain and the soil here is mainly slope clay. This means infiltration is not possible and to relieve the stormwater network, we are supposed to feed in stormwater at 1l/s. According to the development plan, it is specified that there must be 3000l retention volume per 100sqm of sealed area. The circumstances leave us no other choice.

Therefore my question is whether, instead of a retention throttle with a lifting shaft, I can also adequately drain the retention volume with a throttled submersible pump? Or would the purpose association come down on me because that is too susceptible to manipulation?
 

borderpuschl

2022-11-03 08:27:39
  • #4
Unfortunately, I can't think of a solution here either. But keep in mind that the cistern also has an emergency overflow DN 100. This would also have to lead directly into the RW channel. How do you want to solve the problem if the cistern is full due to prolonged rain and the pumping capacity to the downstream is not sufficient?
 

WilderSueden

2022-11-03 09:38:34
  • #5
When retention is mandatory, the volume cannot be used effectively but air has to be buried. We have that too. Is there a way to set the cistern higher so that the overflow and the retention drain with a slope? Or to raise the cistern via another cistern, e.g. a flat tank?
 

mutzbratem

2022-11-03 13:19:03
  • #6
Thank you for the answers and suggestions. Today I finally had a nice colleague from the ZWA on the phone. He sent me a few forms that show how I can drain.

Type 4 applies to me. That clears everything up. I will discuss the rest with the sanitary technician because he will design and supply the retention pump for me.

Nevertheless, many thanks to you all!
 

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