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Foundation Drain Tile Installation

Foundation Drain Tile Installation

Foundation drainage tile systems are one of the most important aspects of residential construction. Drain tile systems are also one of the most misunderstood aspects. Because these systems are usually deeply buried and cannot be easily modified or corrected, it is vitally important that they are installed correctly. Foundation drainage systems which are installed properly can serve a dual roll.

Many homes around the nation have full or partial basements. These basements are really reverse swimming pools. In other words, most people don't want water in their basements. Foundation drain tile systems act as the means by which ground water can be transported away from your basement. If you want a dry basement, you must have an adequate foundation drainage system.

The water content in the soil surrounding your house can fluctuate seasonally. There is always a point at which you can dig and hit water. Geologists often refer to this as the water table. This water table rises and falls in response to the amount of precipitation in any given time period. The water table in many parts of the country can rise to within a few feet of the surface during wet spells. Water will take the path of least resistance. It can choose to go sideways through a crack in your foundation, or it can go down alongside your foundation into a pipe. I'm sure that you will agree that it is a better idea for the water to go down the pipe.

A foundation drain tile system has four main components. The drain tile (pipe), the filter media (gravel), the gravel cover, and the water outlet. All of these elements must be installed for the system to function properly.

The drain tile or pipe is usually 4" in diameter and is perforated or has pre-drilled holes along its length. Depending upon the type, it can be purchased in rolls up to 250' or in 10'sections. Fittings are available to allow you to go around corners or interconnect the pipe.

The filter media or gravel is used to cover the drain tile. Water can flow readily through this gravel and find its way to the pipe. Remember, water takes the path of least resistance. Some soils (heavy clays) resist water movement. If your soil is like this, the water would rather go sideways into your basement than down through the clay soil to the drain tile. The gravel that is used most often is large (1 - 1 1/2" diameter) washed rounded gravel.

The gravel cover is a barrier which keeps silt and mud from clogging the gravel or the draintile pipe. During excavation, dirt removed from the hole is "fluffed." This means that it is disturbed and broken up. It is loosened further during back filling procedures. All of these small dirt particles (silt) can be easily carried through the gravel by the rain water or snowmelt which enters this soil. Without a barrier, these silt particles immediately clog the gravel and drain tile and render it useless. A wide majority of builders often do not install this barrier. The materials commonly used are straw or tar paper.

The water outlet is simply the place where the collected water flows to. It can be one of three places. If you build on a hillside, your drain tile will simply 'daylight' or come to the surface. This is the best situation, because your system depends entirely on gravity to work. If you build on level ground, you have basically two choices, install a sump pit or a large buried French drain. A sump pit is usually installed inside the basement of your home. The drain tile pipe runs beneath the footer to this sump. The collected water is then mechanically pumped from the sump. A French drain is a large subterranean pit filled with gravel. The drain tile pipe runs to this pit and the water fills this pit. French drains do not work well in areas where the water table rises above the level of the basement floor.

Installation Specifics

Drain tiles work most effectively when placed along side of a foundation footer, instead of on top of the footer. This practice allows you to lower the effective water table an additional 6-8" below your basement floor. In new construction, install the drain tile immediately after the footer forms are removed. Cover the pipe with gravel to a level flush with the top of the footer. If you choose to wait until the foundation is poured, there will be less room to work in, the side walls of the excavation could cave in, or extra concrete from the foundation pour could fall into the hole and have to be removed. Believe me, it is faster and easier to install it without the foundation walls in the way.

After the foundation walls have been water proofed you begin step two. Backfill over the pipe with at least a three foot thick layer of gravel. If you can afford it, backfill with gravel to within 18" of the finish grade. You must think long term. Remember, it will be virtually impossible to dig up and add gravel in the future when your basement is leaking. The extra money is well worth it.

Once the gravel is in place, cover it with a 4" thick layer of straw or a single layer of 15# roofing felt paper. This barrier will prevent the silt from the backfill dirt from clogging the gravel and drain tile.

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18 Responses to Foundation Drain Tile Installation

  1. I am wondering if a French Drain would help solve the water problem in my crawl space. My house was built late 70's. For whatever reason, the crawl space floor is lower than the yard on the exterior of the house. The back yard does slope towards the house, which helps bring extra water into the crawl space. Basically, they did dig a trench around the interior foundation of the crawl space, to direct water to the front yard corner of the crawl space. At this time, we siphon the water out as it accumulates. I am sure a crawl spacea sump would help as well, but I may not need that at all if a French Drain would work. Please let me know your thoughts. Thanks so much.

    • Damon, your question requires lots of typing, plus I have some questions for you so I can give you the correct answer(s). I only do pithy answers here in the comment section. If you want to protect the investment you have in your house and not waste time or money *hoping* you make the right decision, you should talk to me on the phone for just 15 minutes. It'll be the best investment you've ever made in your home!

  2. The drain tile entering my 24 inch deep pit are 1 inch from the bottom. My pump doesn't engage unroll the water level is 2 inches above the tiles. Then it takes up to 3 minutes to pump out the back logged water. Should this be changed?

  3. I need to redo/install new drain tile for my mother. I know and have found all the basics and done extensive research on what are the best ways to do it, what the best tools are, what pipe and gravel and gravel cover to use etc....however...I absolutely cannot find ANYTHING about the drain tile for a split level home. I need to know what to do where the sub basement drops to the lower basement. Do I just run a pipe straight down to the next level or does it need to be on a small angle??? Or is it different all together when it comes to a split level home???

  4. Tim,
    My home was built in the late 40's early 50's using a concrete foundation. the problem is water leaks in thru the corner walls some springs. last spring it was 5 bucket fulls, this spring it was just a bucket full & some springs none at all. i notice i have two sump pits with one pit having a pump. i looked into the pit the other day wondering why this thing isn't draining and i noticed there is not any drain tile or pipes running into either pit but both have water in them. i don't understand were the water is coming from in the pits or why i am leaking.

  5. I want to install drain tile in an old limestone basement. The rule is 6 inches away from the wall along the footer. I have an old lime stone foundation that has no footings. Could I start breaking concrete 6 inches away or do I break concrete next to to the walls and lay the drain tile along the walls. My fear is would the foundation give if I break concrete alond the walls. I never have installed on a limestone foundation and this is for inside the basment. Thank You

  6. We are in a building that is suppose to have a drain tile around the outside of the entire footing and then go to a sump pump for expulsion of water. We have found out that only a small part of the tile was put in at the time it was built. We have a finished basement, and would like to have someone dig it up and properly install a drain tile around the outside of the footing, as our city code calls for. Who would I be trying to hire for a job like this? Any info you can supply would be greatly appreciated!

  7. Is it best to place interior drain tile around the entire perimeter of the house? Someone suggested we only do it on what would be considered the "upstream" side.

  8. I am going to build a house in Morelia mexico and on sloping (18"/10ft). The rain is very heavy july and August and dry the other months. bedrock is 6 ft deep on the high side and 8 ft on the low side. 6" deep cracks at end of dry season. I am going to use fill with crushed volcanic local rock (local) to 3 ft above the high side for the slab and the stepped footing 38" into the clay soil with block to slab level. Question: do I drain tile the outside footings or set piers at the intersections of the bearing walls to bed rock? which is less effective? or is there another way?

  9. I have a 1960's brick rambler on a septic system, with a sump pump. During a recent week of heavy rains, the drain outside the basement door had water coming up through it. None of the drains inside the basement were flooding. Any thoughts as to what the problem could be?

  10. I have a room in my basement that is finished and it does not have drain tile is it possible to put drain tile about 8 inches away from the footing and then I could hook it to my old drain tile that is in the rest of the house. would this work

    thanks tim

  11. I have two problems during the wet season, leakage at the wall/floor interface, and small amt of water from cracks in the foundation walls. I also have window wells that fill up during heavy rain(not from the top, they continue to fill over the next few days). My sump pump is working. My question is, I have a 1948 home with poured concrete walls. Is there anything specific about this era of home that needs to be addressed, or does this sound like typical basement leakage?

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