Forgot the wall collar at Kabuflex - how to seal it?

Hello everyone,

I hope someone here can help me.
Recently, our floor slab was poured – we do not have a basement. Around the floor slab, a frost skirt with a depth of 93 cm was installed. Under the floor slab, 3 empty conduits were led outside. Two of these are KG2000 pipes and one is a Kabuflex pipe.
For the KG2000 pipes, collar bricks were set before pouring the floor slab. Unfortunately, this was forgotten for the Kabuflex pipe.
Here is a picture of how it looked before pouring:

And here is a picture of how it looks now:


The conduit comes out approximately 20 cm below the ground surface outside.
Because of the missing collar brick, we are worried whether water might enter the house later on.
To my understanding, due to the frost skirt, water forming under the floor slab can be ruled out and therefore no water can enter the building from below the floor slab at the edge of the pipe.
Is that correct?
The only possibility for water would therefore be at the conduit’s exit at the edge of the floor slab.
Is there a way to seal this exit afterwards?
Around the house, a 30 cm wide and 10 cm deep gravel layer will be installed.
Would it help to make this gravel layer 20 cm deeper at the point where the conduit exits, so that the conduit ends within the gravel layer?

Were all KG pipes executed with collars, including WC, kitchen, everything?

With us, no pressing water is expected and we did NOT get any masonry collars installed.
Only our roofer sealed the pipes on the base plate with liquid bitumen stuff during the bitumen waterproofing.

Yes, all KG were executed with collars - at least as far as I can still judge based on the pictures. Only with [Kabuflex] this was not done - for whatever reason. Now the question arises for us what problems this can cause. Can pressing water occur at a depth of 20 cm? In the soil survey, I find nothing about pressing or non-pressing water.

By the way, bitumen sealing sheets were also laid with us, but nothing was done with liquid bitumen. How and with what exactly was it done with you?

Can pressing water occur at a depth of 20 cm?

Yes, with 1m of floodwater around the house, you no longer worry about the floor slab because the house is then filled with 1m of water anyway.

A wall collar around a Kabuflex makes little sense, because 1) the wall collars are fastened with stainless steel clamps and are therefore only applicable to rigid pipes. 2) The KG pipes are specially coated and thus very smooth, whereas the Kabuflex, due to its shape, has significantly more surface contact with the concrete and therefore acts much more as a sheath surface than as a sealing surface. Nevertheless, it is not truly watertight against pressurized water. However, if your soil report shows no accumulating, pressurized, or groundwater, there is no need to specially seal within the concrete layer here. Presumably, a membrane will be glued onto the base plate later, or, as in our case, a multi-flange plate installed.

From the manufacturer of Kabuflex, we have received the information that the pipe is made of polyethylene and this material does not bond with concrete. As a result, water could seep along the pipe into the building. There are also special wall collars for Kabuflex – both from the manufacturer and third-party suppliers. That is why we are so uncertain. Do we generally understand correctly that, due to the frost skirt, no water can form at least below the floor slab? What do you mean by membrane? Only the bitumen sheet was glued on in our case. Would it be an idea to simply fill the outlet of the empty conduit a bit with construction foam?