Downpipes - do they actually drain anywhere?

[harrythefurrysquid]

This is probably a bloody stupid question, but here goes:

The downpipe on my detached garage disappears into a drain hole. This hole is full to the brim with water, and when it rains heavily the downpipe fills and water spills out of the gutter. I did have a bit of a poke around in the drain hole and honestly it just feels like a soft-sided hole maybe 6-8" diameter and maybe 2 ft. deep. I could not feel an obvious outlet.

Would you expect this drain to actually go anywhere, or does it just filter water into the soil? There is a sewer manhole about 15 ft. away so it could plausibly run to there with a run of pipe under some concrete.

Basically poking about in this hole isn't all that fun so I want to know if there's actually anything to unblock.

 

[DiyNutJob]

It wouldn't be called a drain if it doesn't go anywhere. If the opening of the drain isn't protected from debris, then eventually it gets blocked.

Wait until dry weather, extract all the water from the drain and see what you have got. The drain shouldn't be soft-sided. It's should be plastic drain pipe.

 

[Mottie]

The downpipe on my front porch goes into a drain hole that is filled with gravel. It’s a mini soak-away. When we have a thunderstorm with excess rainfall, it overflows but is all gone within half an hour or so of rain stopping. I wouldn’t think a garage roof would go into a 'proper' drain.

 

[DiyNutJob]

When we have a thunderstorm with excess rainfall, it overflows but is all gone within half an hour or so of rain stopping.

So, somewhere near blackwall tunnel is a property without a proper drain? This is very unusual because the infrastructure would be well developed in town.

 

[Mottie]

So, somewhere near blackwall tunnel is a property without a proper drain?

I don’t live anywhere near Blackwall tunnel.

 

[oldbutnotdead]

Depends how and when it was built. If you have a biggish garden it might be draining into a soakaway (dig hole, fill with gravel, cover hole). Or it might be connected to your manhole (lift the lid and have a look). Or it might just be draining into the ground- not unknown for people to take shortcuts with gutter drainage

 

[harrythefurrysquid]

Hmm, OK, thanks all for input.
Sounds like the answer is... maybe

Waiting until a dry spell next summer sounds like the way to go. Honestly I do suspect it's supposed to go somewhere because of the proximity to the manhole, but equally it's just a garage roof drain so it's also completely possibly it's literally a buried pipe with some holes and gravel.

 

[blup]

The soft soil could be whats built up over the years in the drain. It possibly goes into the main sewer.

Blup

 

[robinbanks]

If you're keen to do it soon, a hosepipe and a wet vac should help clear the drain gulley pot out quickly, so you can see where it goes. Probably shaped similar to this:

If it's missing a cover (quite typical) having been filled with leaves etc that have rotted over the time it'll seem to be full of soil or sludge but if you can get the drain pipe moved aside to give more working room you should be able to feel the exit pipe be above the area where sediment accumulates. The exit pipe may run in the direction of the nearest manhole, or the nearest other gulley pot - it's quite usual to chain them all together with drainage and then just discharge into one manhole or a soakaway. Filling one with gravel and burying it would make for a poor soakaway - soakaways need to be quite large

 

[harrythefurrysquid]

That looks like generally the right sort of shape for what I could feel, though the entrance is only drainpipe size.
I couldn't find a side-exit though.