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Help with drainage problem.

5K views 25 replies 10 participants last post by  call811beforeyoudig 
#1 ·
I need to run storm water drainage for an area where I laid patio blocks. I included a MS Paint picture of what I was planing on doing. I'm basically going to buy those box grill drainage parts and interconnect them with pvc pipe. I will run the underground pipe to a shallow trench at the edge of my property line. I have a few questions though.

-Do I need to slope the 4" underground pipe that goes to the trench?

-How much do I need to slope the patio blocks to the center where the grills are located?

-Do you have a better suggestion to remove storm water from this area?


Thanks
 

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#3 ·
Yes you do need to slope the pipe, otherwise how will the water get to the trench. I would slightly slope the pavers too, but if you prepare the ground underneath with a sand bed on sloped undisturbed soil or geotextile fabric, the water will permeate through and make it's way to the grill as well. Bump for more opinions.
 
#6 ·
The problem I am having is that the trench is around 35 to 40 feet away from the first drain grill. The trench is only 6 to 8 inches deep. I can't really dig the trench deeper because of liability issues. I don't want my neighbor kid breaking his leg in the trench while playing. At 1/4in drop for every foot, I am looking at 10inches at the trench. This doesn't include the 3 or 4 inches under grade that it states off at. I would be looking at a trench at a minimum of 14inches. I thought it would drain if at level because the entire pipe is below grade. It would have to drain if it fills with water.

I haven't laid the patio blocks yet.
 
#8 ·
The problem I am having is that the trench is around 35 to 40 feet away from the first drain grill. The trench is only 6 to 8 inches deep. I can't really dig the trench deeper because of liability issues. I don't want my neighbor kid breaking his leg in the trench while playing. At 1/4in drop for every foot, I am looking at 10inches at the trench. This doesn't include the 3 or 4 inches under grade that it states off at. I would be looking at a trench at a minimum of 14inches. I thought it would drain if at level because the entire pipe is below grade. It would have to drain if it fills with water.

I haven't laid the patio blocks yet.
Can you not dig out the trench, lay the piping and then back fill with gravel afterwards. You need that depth.
 
#12 ·
How do I measure the drop? I was going to just pull some string across (sidewalk and trench). I would then put a level on the string and see what the difference is at the trench. Is this the right way? Also, How much should I slope the pavers to the center where the drain is? Is 1 in every 10 ft sufficient?
 
#10 ·
I can't bury the pipe at the trench because the trench leads to the street. It would create a huge trap. I attached another picture. The water would have to drain because it will take the path of least resistance which is out the other end at the trench. I could have problems with stagnant water though. I can't really slope the patio away because there is a structure on either side. If I slope it to the trench, I will have a huge puddle in the yard every time it rains. The trench goes another 25 to 30 feet to the road. The first picture isn't to scale. The trench isn't that close to the building.
 

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#21 · (Edited)
I don't think a dry well will cut it. Too much water falls off the roof into this area. Gutters are out of the question because they clog up too much. I'm going with a slight slope on the drain line. It has to drain. Even a trap will drain at dead level if the inlet is higher than the outlet. I can't slope the patio towards the patio because it will flood my yard. I already have a flooding problem in that area.
 
#22 ·
could you solve this problem by digging an extra deep base, filling most with compacted fine stone, then a thin layer of compacted sand, and setting the patio block on this. that way the water goes downbelow the surface and dissapates that way. kinda like a dry well under the patio
 
#23 ·
Thanks for the reply. The only problem is that I live in Florida and we have a lot of clay in my area. It hasn't rained in about a week a half and the ground is still wet when I dig about a foot and a half down. I'm worried about the foundation of the structures. I would rather get the water out of there. The pipe is going to be pretty low by the time it hits the gully. I might have to dig a swale instead.
 
#24 ·
Why don't you consider a French Drain. The slope will all be subterranean and therefore avoid the "trap" you would create by an obvious above-ground trench. I placed one at the base of a stone retaining wall that runs up-hill from my patio.

You will need to exacvate the slope as indicated, but the backfill the trench with course (1"-2" or larger) gravel. With a good base in the bottom of the trench you lay a perforated pipe wrapped in landscape fabric. This pipe should be sloped. Cover the wrapped pipe with more gravel. On top of this, lay another layer of fabric. You can re-place your stone on a bed of sand. The water will permeate the sand, filter through the gravel and into the perforated pipe and out.

This worked for me. I live in East Texas with a sand, red-clay mix.

Water is going to go where it wants to go. It will always seek the lowest point. You just have to be a little bit smarter.
 
#25 ·
It ended up being really deep at the gully. I only sloped the pipe a half inch for every 5 feet. I couldn't dig a swale, so I decided to run the pipe to the road. It was an additional 45 feet of pipe. I couldn't run the last 45 feet with any slope at all. I just left it completely level. It drains perfectly fine. I tried to inundate it to no avail. I poured a few 5 gallon buckets of water down the main basin and had a garden hose tied to another inlet.
 
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