Drainage solution not keeping up with downpour.

Probably a partial clog somewhere. More than likely roots.

Have you checked or tested the outflow end, it's probably clogged. Or try running the hose through it.

For capacity, you want your underground rain drains to drain to daylight.

Figure out where these drains are supposed to discharge.

If they have no discharge, the discharge may have become buried. Or the drains may have been slotted, which can become blocked by roots. Roots also get into couplings. A continuous run is the only corrugated pipe that doesn’t end up with root penetration.

You may need to replace these drains to have them drain to daylight. You could use rigid glued PVC to help avoid sags and root penetration. It’s a lot of digging. But it’s done once if it’s done correctly.

Make sure controlled overflow point is away from the building.

Clogged, and honestly, running to the ground is just a hassle. If it doesn’t run to a storm drain then run it to the street.

These buried drains fill with leaves, roof granules, and roots or dirt. Since they are buried there is no easy clean out.

1) find the outlet and make sure it is not blocked. 2) you can try to extend the sweep by putting a couple of 45s in the line instead of the 1 piece of flex pipe. 3) you can also change the 1st part of the run to double wall ( smooth inside) pipe as it has a lower friction coefficient than the single wall pipe, thus it will accept a higher volume of flow

During heavy downpours...the amount of water being diverted into those pipes at once..they will always backup a little.

I have the same thing...only happens during heavy downpours.

Gutters have probably washed down leaves etc which will clog the drains. Why not get a pipe extension fitted and drain into your garden . Or better yet, fit a water butt to the pipe and save the rain for flowers

Used to have a girlfriend like that, would get pretty messy but fun as hell!!!

Downpours will be downpours, but we need a pick of the discharge end to know what’s up.

Everything reminds me of her

But on a serious note check your outflow, though the downpour seems significant, is that normal for your area? Or a significant downpour

A good why YT channel drainage. https://www.youtube.com/watch?v=jFm0-xfU4Vw&t

If you can’t find the end, you can throw smoke bombs down the black pipe. Smoke should come up at the other end. I tried it but it didn’t work, but on YouTube it worked

You need to add rocks or gravel to drainage area. 

Clogged. Remove the black pipe from the bottom and use a diverted to slough it away. Its impossible to clean these downspouts and know that the underground pipe is fully clear, so they just never get cleaned until they clog and you have to dig them up. A $200 gutter cleaning becomes a $1000 gutter cleaning/repair.

This happened to me. I ran a hose down mine with a high pressure nozzle to clear it out. There were root and rocks etc. Better now.

Add a dry well for the drain. It is technically easy to install just some digging.

Install gutter covers too.

The cheap builder may not have built a dry well (6 feet from the house);if it isn't blocked. It shouldn't be going to the house drain tile.

There are plumber plunger wired about 6-7 ft long get it and try first.

You need to add rocks or gravel to drainage area. Helps prevent puddlinh.