ᐅ Should I drill an additional inlet into the rainwater catch basin?

Hello everyone,

I am currently considering the best way to drain the roof area of the soon-to-be-built carport.
At a distance of 4.5m (15 feet) from a possible post location for the drainage, we have a rainwater catch basin installed for the downpipe draining the house roof:
[IMG width="185px"]https://m.media-amazon.com/images/I/61Cr0iIPwyL._AC_SX679_.jpg[/IMG][IMG width="213px"]https://m.media-amazon.com/images/I/51veIrweQpS._AC_SX679_.jpg[/IMG]

Both the rainwater catch basin and the carport post are located at the eaves edge.
My idea was to lead the drainage from the carport post to the existing catch basin. However, since the pipe should ideally not be visible, I would have to run it below the gravel in the eaves area.
A 2% slope over approximately 4.5m (15 feet) results in a 10cm (4 inch) height difference, so I would need to cut an additional side opening at the lower end of the basin.

Do you see any problems with this? Possibly with sealing the additional opening? Has anyone perhaps tried this before? I have not found any ready-made basins with an additional side inlet.

Is installing a T-piece below the rainwater inlet box not an option?

sysrun80 schrieb:

Is installing a T-piece below the rainwater collection box not an option?

I thought I could use the filter of the rainwater collection box at the same time. There aren’t any tall trees in the new development area yet, but I’m worried it might get clogged after a few years. The water goes into these buried infiltration tanks, not into the sewer system.

You can install a sieve/separator at the carport; it doesn’t cost much. That way, you have a clean solution without any makeshift arrangements.

The drainage is hidden inside the post. That means there is a DN75 outlet relatively low on the post. From there, I can continue onward.
So far, I have only seen such cutting tools used for installation in downpipes. Are there other options? What should I be looking for?

Of course, one could use a second rainwater inlet box, but then I would already be very deep in the eaves edge at the beginning and would have to excavate quite a lot again.

If it's just about leaves, simply install filter baskets in front of the downspout on the carport. They just slip on and that's it. They come in all sorts of styles.