Underground downspout drain, how to terminate?

I've purchased 4" PVC pipe to drain two of my gutter downspouts into and out the back yard about 10-15 feet away from the house on a slight downhill slope.

I'm just not 100% sure how to end the drain. My original idea was to place a T at the end of the 4" pipe, one end of the T would face down into the ground emptying into a 2-3 hole lined with landscaping fabric and filled with rock. The other end of the T placed just at ground level with a grill on it. The idea would be to allow the water to drain into the ground, but when the ground got to saturated with water it was overflow the top out the grill and then continue down hill away from the house.

I was told this wouldn't be enough since the ground has a lot of clay in it and the hole would just fill up in no time, but instead would need to use a large barrel, such as 55 gallon barrel instead of just a 2-3" hole with rocks. Along with the top grill for over flow.

What are your suggestions?

 

If you have clay soil, I can see the logic in creating a bigger dry well.

I like your idea with the T and the overflow - do you have it flowing into some rocks or something else on the surface to mitigate erosion from the stream?

 

In my soil a French drain of any size will not work0. So much water comes down the gutters that it would take a very large French drain or very porous, sandy soil. My drains have the full flow run off on the surface. I buried my 4" drain pipes and let the output end run long. I back filled and graded the area then cut off the end of the drain pipe at about a 30 degree angle with the top corner flush with the ground surface so I can drive over it when mowing. I would not install a grate since that will just catch & clog with debris washed off the roof.

 

Dane - I thought about doing the same thing you have done. My concern with that method is how much erosion would be caused by that much volume of water being poured out the pipe.

While mitch17 is correct about some erosion from my above idea I wouldn't think water over flowing from the top would cause nearly as much or as drastic as water flowing down a 4" pipe directly onto a hill side.

What steps have you done to migrate erosion?

 

At the very beginning there was erosion since we got some heavy rains before the grass was well established so I had to re-do the channel where it washed. Eventually mother nature cooperated and I was able to get enough grass in place to hold everything and it has not been a problem since. All of my pipes outlet in open lawn with full sun so the grass can grow well. If your area is shaded you might have to bury a concrete paver or stepping stone to help spread out the water and slow it down a bit before it hits the soil. You could also try anti erosion netting or rolled straw.

 

Dane you and I are having a similar situation. I had a 4' PVC Pipe installed underground that runs 81 feet in a down slope down the side of my yard. The 4' PVC Pipe is connecting 2 drainage down spouts and my sump pump. Everything is flowing just like it should the problem is the water has filled up the drainage pit which is (3 feet wide and 2 feet deep) and is now creating a swampy area in the back of my yard! I agree I am not 100% sure how to end the drain. Lowes and Home Depot said get pea gravel and fill it half way, problem is there is still water! I see that you lined your drainage pit with a weed fabric of some sort does that work and is the T helping control the water flow?
Tim