How to terminate a soil drain pipe into the earth and avoid blockages

Question

Is this advised? How would I set up the end of my drain pipe so as not to get a backflow of dirt and have the pipe get clogged. I'm thinking rock, then black cover, then more rock, then dirt, with the drain pipe end pointing down. I also drilled some holes over the last foot of the end so water can escape out the sides.

I haven't seen many resources online talking about how to terminate a drain inside the soil, so I'm wondering if what I'm attempting is a mistake. It was a last minute idea but I do like how it looks. It will drain about a quarter of the roof and I'm pretty sure it's far away enough from the foundation but I can extend it a few more feet.

Answer 1

Normally you would put that into a "dry well" to terminate it underground. That's a large, perforated drum-like thing. 50 and 330 gallons are common sizes, but there are many others.

It's also common to have it terminate above ground, by ending with a "pop-up emitter" which sits flat on the ground so as not to interfere with lawn-mowing until water flows from the downspout in sufficient quantity to "pop" it up so most of the water can run out onto the lawn surface. Indeed, you might want one of those to release excess water if you have a drywell and the drywell fills up.

I expect you'll find it fills completely with water and cannot drain fast enough when you have a significant rainstorm.

I'd also say it's too close to the house, even without a definitive measurement. It eyeballs as no more than 6 feet / 2 meters. 10-12 feet / 3.3-4 meters is a more common minimum distance recommendation.

Answer 2

Just finished landscaping my garden.

They diverted the drainage pipe in a pit where my rainwater tank got embedded with crushed rock. Then they covered the crushed rock with water permeable geotextile, to prevent soil infiltration of the crushed rock. Afterwards soil.

I don't know what size of pit would be advisable, as I had a 3 x 3 x 3m pit excavated for the rainwater cistern. Most likely a much smaller would have sufficed easily.

My drainage was only for the diversion of a french drain. For a roof drainage I would have relied on an specialist or the local building office. A google search revealed the existance of specific formulas involving the expected maximum rain, the type and size of roof, the permeability of the soil and certain factors defined by local building code. Therefor an globally valid answer isn't possible.

That being said, I am confident that the flowerpot sized hole in the question isn't enough, and is a sure way to make an nice sinkhole.

Answer 3

Too large for a comment to https://diy.stackexchange.com/a/280284

(just as example) the image below shows such a dry well: If it rains, the water infiltrates between the crushed rock surrounding the yellow perforated pipe. If it does not just rain but there is a rain storm and the water cannot infiltrate into the ground fast enough, the water uses the black "emergency exit" on top and runs over the surface. That is way better than filling back and spilling nearer to your house. (And after several years you might want to open the black cover and get out any dirt which accumulated inside.)

Image from here

Answer 4

You can terminate these pipes underground in a dry well, with a mix of sand and coarse stones, as some of the other answers have outlined, but I strongly urge against doing so, because doing so makes what is going on underground invisible without excavating the whole area. What this means is that, if at any point down the line, you get a blockage and/or backflow, you have to dig up a huge portion of your yard just to access the area to figure out what is going on, let alone to fix it.

The probability of having to redo this in the long-run is high. A lot of things can go wrong:

• Over time, sediment can clog the drainage, so a size / drainage that was adequate initially, might not be in the long-run.
• A change to the environment, such as a change that makes more water drain into the soil, or an increase in severe rainfall events, or a change to the roof that leads more water to run off into this pipe, can make it so that you will need more capacity later.
• You might not size the well or drainage basin large enough to begin with, and it might be okay for a while, but you won't realize that it's big enough until you have a severe rain event. If you don't do this sort of work professionally, the chance of you sizing it wrong is very high. And because the sizing needs to be chosen on the basis of rare events, you might not realize that it's too small until months or years later.
• Changes in the surrounding hydrology which lead to an increase in the height of the water table could decrease the drainage rate or cause backflow, even if the amount of water flowing into the pipe stays the same.

A better option is to simply dig a basin that is open to the air, and then do the same thing: put a layer of sand at the bottom and then rocks on top of that. In this case, troubleshooting is very easy, because you can see exactly what is going on at a glance. Fixing a problem is also much easier, as the space is accessible. If the basin is in an area where the stakes are low for overflow (such as if it just runs downhill away from your home and/or temporarily floods an area of lawn) you can even dig these sorts of basins incrementally, like dig it, and every time it overflows, just dig it wider and/or deeper to increase capacity.

Furthermore, you get the very large benefit of being able to plant a rain garden around the edge of the basin or even in the basin, in which you can grow wetland plants or other water-loving plants that you might not have enough water to grow normally. So having the basin exposed actually becomes an asset. For eaxmple my yard is too dry for swamp rose mallow (Hibiscus moscheutos), a really beautiful perennial which is native where I live, but I have been able to grow it in a rain garden supplied by the downspout from the front slope of our house's roof. I have seen all sorts of different ways of doing these rain gardens or basins, you can have plants around the edge and open stones in the middle, or you can have the entire basin planted like an artificial wetland. Both options can be attractive, and typically it's a lot less work to maintain than mowing a lawn, you can mow or cut the plants in them once a year and periodically weed, but if the plants are chosen well for them they won't need much weeding.

So this is how I'd approach it. Yes, you can put it all underground but the chance of you regretting it later and creating a ton of extra work for yourself if you have it all covered up is very high. Just keep it out in the open and your life will be much easier.

Answer 5

If you would just terminate the drain hose in the soil it would immediately back up in the rain because the end in the soil would not have enough flow conductance to drain away significant volumes of pooling water. You must either conduct the water away to a surface path or to a high conductance underground line to a ditch or to the street or the alley.

In our tract house in Dallas TX we do not want water pooling next to our foundation but we don't want to rush rain water to the street or alley where it would go into the storm sewer. We value rainwater and have contoured our 10,000 sqft lot to retain as much water on site as we can.

The street in front of our N-facing house slopes up a moderate hill to the E, about 3 ft/100 ft. Hence our 87 ft wide lot slopes down to W. The 2500 sqft house (2050 living space + 450 integral garage) is approx square in plan and has a straight gable, low pitch (3-in-12) roof (ridge N-S) so the water is shed off the roof to the E and W sides without gutters and downspouts.

The house is off-center on the lot because it has a W side patio. The E side of the house (bedrooms with high windows on the E side) is only 8 ft from the E property line (neighboring house to the E is uphill); W side of the house is 38 ft from the W property line. This gives a generous W side yard and back yard.

Once on the ground the water on the E side is collected in a swale and drains toward the N and to the S (respectively, toward the street and the alley). We try to drain the water to the front where it can pool on the front E side and so drain slowly into the soil.

Water from the W side roof drains in a sheet to the W and to the front W side where we also promote pooling to soak into the soil.

Answer 6

The effectiveness of this "well" depends on your soil. Some Places are clay for some distance, such as 15 feet, it is impractical in such places, however we live on a glacier created sand plain in Minnesota. The capacity of absorption is basically unlimited, although the rate of absorption is controlled by the depth and diameter of the well. Normally within 5 to 15 ft in our area you hit the surface water table. If you live in an area where you hit sand or gravel within 10 ft of the surface you are fortunate and you will most likely have almost unlimited absorption capacity (again the speed of absorption is determined by the diameter and depth of the well above the water table, the deeper and bigger the pipe the faster the absorption rate).

At 6 ft I have a 8 inch free standing extruder well that can absorb about 5 gallons a minute. A 10 inch well would absorb about twice that. Our city has several of these that are 24 inches in diameter and about 10 ft deep. They look like a common storm drains and have incredible capacity. In my case I need it in the spring while the ground is still frozen. The bottom of the well being below the frost line can absorb most of our melt.