ᐅ Infiltration of Rainwater: Which Method to Choose?

Created on: 20 Mar 2017 10:16
3
305er
Hi,

we’re about to start building soon, and the building permit-free process was not objected to.

However, on the advice of the construction manager, we informed the local authority that rainwater would be infiltrated via a soakaway basin in the garden.

The authority states:
Rainwater must be infiltrated; a calculation of the infiltration system according to ATV-DVWK A-138 is required and must be documented. An infiltration test or an equivalent laboratory test is necessary.

We have no expertise in this matter ourselves. I’ve tried to read up a bit, but the whole topic seems very complex.

As mentioned, we specified a soakaway basin, so the local authority was able to approve it directly and did not have to forward it to the lower water authority.

One neighbor in our new development installed a soakaway tank and prefers it over a basin because it doesn’t create a “wet biotope” in the garden.

Another neighbor who has already built (using the same earthworks company/gardening contractor as we are) installed a trench soakaway system.

Now I’m wondering which option is better or more cost-effective?
Attached is the offer, which also includes the trench soakaway.

The soakaway tank seems to be quite a bit cheaper??

I hope you can help me decide the best infiltration method.

Textdokument eines Bauangebots mit Tabellen und Preisen
RobsonMKK21 Mar 2017 06:53
@Alex85 It depends on the size. Of course, in this case, you should use soil that is most suitable for infiltration. But the contractor also needs to make a profit somewhere.

For comparison, regarding the infiltration trench/filter pit system: was everything considered for the filter pit, or were only the prices for the filter pit taken into account?
305er21 Mar 2017 09:13
Only the price for the igloo was taken.

The position with the pipe also relates to the infiltration trench (or soakaway).
RobsonMKK21 Mar 2017 09:20
However, there is probably more involved with the infiltration trench (rigole) that you might not have considered yet for the infiltration chambers (Iglus).

You also need an access point for maintenance, ventilation, and filter fleece to prevent the chambers from silting up. This means the costs will quickly become similar. Another advantage of soakaway crates (sicker boxes) is that they can be installed deeper, whereas infiltration chambers can only be installed horizontally.
305er21 Mar 2017 09:45
So I quickly looked it up, and it’s not that expensive. It also seems to be a complete system.

Cross-section of a drainage system with pipe and filter material around the pipe
RobsonMKK21 Mar 2017 09:49
Then please try to get a calculation according to AW 138 for that.
And honestly, there should be a noticeable difference between products from OBI and those from Graf, Intewa, or similar manufacturers.
305er21 Mar 2017 10:03
Yes, that is probably true, but “no name” products are not always bad.

For the basin, a volume of 3.3m³ (116.5 cubic feet) was calculated.

Technische Bauunterlage DWA-A 138 Versickerung Bemessung Tabellen