ᐅ Rainwater from the roof – underground drainage for disposal?

Hello,
we are currently in the construction phase of a single-family house, and I am considering where to direct the rainwater from the four downspouts. Generally, there don’t seem to be any major issues in the area with rainwater infiltration. We also do not have a basement.

I must admit I am a beginner in landscaping. So please don’t take my questions the wrong way.

According to the soil report, the groundwater starts at about 3.80 m (12.5 ft). Therefore, we planned to install a water pump (lower costs due to the shallow drilling depth), so a cistern as a water storage tank seems rather pointless.

I was thinking of installing 10 m (33 ft) of drain pipe connected to each of the four roof downspouts, buried underground. Of course, surrounded by gravel and geotextile fabric.

• Is this oversized?
• Should the end of the drain pipe be left open so that in heavy rainfall, the water doesn’t back up and overflow the gutter?
• Do you see any problems with this plan?
• Should I install a backflow valve at the start of the drain pipe to prevent water from backing up into the gutter? But in an extreme case, the water would then run down from the roof because the backflow valve wouldn’t let water flow down.
• Do you have any other suggestions?
• Am I just worrying too much about the rainwater?

Thanks in advance for your help and advice.