Rain Collector / Regensammler
This is a rain-collector for pipes with a diameter of 98mm.
To seal it up you can use silicone.
You also can use a layer of paint or epoxy resin to make it extra waterproof.
The hose connection is made for normal 1/2 inch garden hoses.
Once the rain barrel is full with rain then it has an automatic stop function.
Everything above the waterline will flow down the pipe till you drain water of the barrel.
Then the same again.
Have fun and follow for more ! :)