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I have a detached garage building that is on a downhill slope and need to put a drain tile in on the higher side so that water goes around it...
I understand the basics and found some good instrucitons online but I can't find but can't find anything that gives the correct "angle" that the pipe needs to be laying at for proper drainage.
Also, this is not a house -- it's basically a steel pole building. I put a concrete floor in. How deep should the drain tile be in this kind of application????
You generally try to find the footer of the building. Dig at least down below that depth, put the drain tile in, it may or may not have a general slope depending on how the footer is installed. As a general rule you want it at least sort of level or a slight slope downhill is desirable.
It is not like a drain line. It is full of holes so it really functions to control the water level in a particular area. In this case you are trying to maintain any water level localized below the level of the footing, hence well below the slab grade. As water rises in the local area it finds its way out the drain system, never coming up enough to introduce water into the structure you are trying to protect.
So there is no magic depth. It depends on how the structure was built. In general you want the drain system below the grade where water could start to give you problems at all points. You have to think in terms of water level, not so much slope of a pipe. It is sort of that old adage water finds its own level. The drain system is positioned to control that water level around the parimeter or sides of a building such that it collects and allows water to flow to stay below a particular level.
If the drain tile does have a slight downhill slope that aids in installation but it may not be completely necessary, it is more about understanding where the water table level you want to control will be. Just don't try getting water to run uphill and get above the maximum water level desired. Other than that the water finds its way out of the system by itself before it rises enough to cause problems.
When in doubt put the system a lil deeper. Things like laser levels or a string level can help in determining long runs and how water will act in the system. Always being deeper in a level plane from the thing being protected is what is required. General rule is to put the drain tile at least its own depth deeper than the footing. You probably got it maybe a foot or so deeper than the slab as a general rule. All depends on how things are built.
What exactly ARE the Footers in a pole barn type building? The Concrete that the poles are in???
I have someone with a backhoe that can dig out the trench but I want to know that it's at the right depth. They aren't exactly drain tile experts.
There was a gravel floor when I moved in and I had a concrete floor put in so I can store stuff out there. Now, I'm getting some water coming in on one side of the building when we have a lot of rain -- and the concrete holds it!
What exactly ARE the Footers in a pole barn type building? The Concrete that the poles are in???
You have to understand how it was built. If you dig down and there is no conventional footer system, just a slab poured on the ground, then you have to go below the slab grade by some amount. General assumption here is the slab is level overall within some reasonable tolerance. The poles are in some type of deep holes with their own encasement. As you say slab was added later.
So in that case something at least a foot below slab grade or you could even go 18" down. All depends on what you are trying to protect, if it is just water at slab grade, a foot down should work, 18" should be overkill. At those depths that would be the top of the drain tile once installed. One guide might be what is the level of backfill / gravel to prep for the slab. Be below that for sure.
Just be sure your outfall runs far enough out on the downhill side to allow water out at the controlled level.
I would have the guy spend more time getting the grade around the building to slope properly, or put in a swale. A drain tile is not going to work well if the grading isn't right.
You don't really need a foundation drain per se, because you really don't have a foundation (pole building). You NEED a site drainage system.
I would have the guy spend more time getting the grade around the building to slope properly, or put in a swale. A drain tile is not going to work well if the grading isn't right.
You don't really need a foundation drain per se, because you really don't have a foundation (pole building). You NEED a site drainage system.
The obvious thing to do would be to change the grade next to the building but that's not the right answer in this particular situation.... My entire lot slopes down hill toward a lake behind.
Prior to my moving in, this garage had a dirt floor. I put in a cement floor so that I could use it. I did not think water would seep over the concrete but it does when you get enough rain. (and we've had a lot of rain this year)
There needs to be some kind of drain next to the building to re-route the water around the building.
A contractor actually suggested the "pipe" idea... which is what I'm calling a drain tile, i.e., a shallower version of what they do to houses.
Why do you think it wouldn't work there?? Seems logical to me that it would....
What is a swale???
Last edited by World Citizen; 09-07-2008 at 04:46 PM..
Many of these water problems have no common solution. It varies depending on the particular site, circumstances, etc. Usually you try to use least efforts first.
One thing to always note, is how the drains come off the building. In many cases the problems can be solved by simply getting the downspouts drainage far enough away from the building or routing it into a particular surface drain path. You would not want the drains coming down directly in back and dumping close to the building.
Those situations where there is a general drainage slope flowing toward a building can be tricky. Ideally all water flows away from a building on all sides. Yes, you may be able to change it by changing the landscaping. That swale idea can work, basically you create a lil depression area that catches the surface flow and route it sideways around the building but it is not fool proof. Same thing can be done by building a small berm next to the building to sort of raise the ground level and cause water to flow around the building.
I might check the building drains first. A simple building surface drain across the back with some perf pipe and gravel should work, it easy to install and pretty fool proof. Messing around moving lots dirt has its own downsides, the visual appearance can be one of them if you are not careful.
Many of these water problems have no common solution. It varies depending on the particular site, circumstances, etc. Usually you try to use least efforts first.
I might check the building drains first. A simple building surface drain across the back with some perf pipe and gravel should work, it easy to install and pretty fool proof. Messing around moving lots dirt has its own downsides, the visual appearance can be one of them if you are not careful.
The downspouts are not causing this and the gutters are clean and working.
The contractor just said pipe -- I'm sure this is what he was talking about. I didn't know the proper term.
How deep should the trench be dug? 12"???
How deep should the pipe be in it??
Do you just fill it in with gravel and no dirt on top???
Yep, in your case I would just go down a foot or so, measured from the top of the pipe. You can line the bottom of the trench and up the sides with plastic, helps keep dirt from filtering in.
Get perf pipe, they make a bell end thin wall that has the fittings built in, designed for the purpose comes in 10 foot lengths or you can get it in a long hose like configuration, in all cases it got lots of lil holes over its length.
I like to make the trench V shaped at the bottom and line it with plastic for these type surface drain applications. You could use a filter mesh instead of the plastic that they make for the purpose, both work. Put the pipe in the bottom, backfill it with gravel, leave the gravel exposed in most cases. Acts as a filter to keep leaves, junk out of the pipes, easy to dig up if you got too. Just plain gravel lets the system have very rapid flow rates, water zips right thru on the worse storms.
You don't got to pay super attention to slope, either level or slightly downsloped is good. Water will find its way out. Just make sure the outfall area is clear and directs the water in the desired direction.
In situations like yours it is pretty close to 100% foolproof in most cases.
In some systems I even directed the downspouts directly into the drain pipes and had it carried off that way. Go into a gravel area for the filtering effect, not directly into a pipe. Never had one of those type systems ever fail to do its job, they are also pretty maintenance trouble free. All the junk collects on the surface and can be raked off, same with leaves, grass clippings, etc.
I can't rep you again but I OWE you ONE ... maybe two or three !!!
THANKS!
One more stupid question, Do the holes on the pipe go UP or down ???
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There is no angle per se......
