Q&A / 

Water Drainage Tips

Water drainage needed to eliminate ponding water

This standing water next my own shed is unacceptable. I finished the shed in late fall and was unable to start to work on the wall and drainage issues until the spring. It can cause many different problems. There are several ways to solve the problem. Look at the after photo below. Copyright 2017 Tim Carter

"Adding soil to the low spots is usually not a good method to fix poor drainage problems. There's a much better way to dry the soil."

Water Drainage Checklist

DEAR TIM: Spring is here and so are the incessant heavy rains. I have several places near my house where water ponds and I need some water drainage tips from you.

It can't be a good thing for my house, as I constantly am battling water in my basement and part of the house that has a crawlspace under it. My lot isn't really that flat, so I'm at a loss as to what's going on.

Do I have to call a professional to solve this issue, or can I just add soil to fill in the low spots? What are my options to get the standing water away from my home? Marion R., Evansville, IN

Water Drainage Solution | Let Gravity Suck Water From the Soil

DEAR MARION: While I don't have accurate statistics to support my feelings, I suspect you're in a vast majority of homeowners who have varying degrees of poor drainage issues on their land or near their homes. You're correct in assuming that ponding water is not a good thing for houses.

How Can a Geology Degree Solve Water Drainage Problems?

A geology degree can solve water drainage issues because water and soil are a core area of study.

My college degree was in geology. I gravitated to two disciplines within geology: geomorphology and hydrogeology. Geomorph, as we students affectionately called it, is the study of the Earth's surface features. Hydrogeology examines ground and subsurface water. I studied these topics for three years while in college.

Both of these areas of geology are especially relevant when it comes to understanding and solving water drainage issues.

If you think about the Earth on a very large scale and take into consideration gravity, you quickly discover that Mother Nature is doing her best to constantly carry all soil, rock, your house, your car, your possessions and you down and into the oceans.

Mother Nature is also a very patient woman.  She also has a split personality.

Her evil twin is constantly pushing land out of the ocean. This tectonic activity builds mountains where two crustal plates crash into one another. This is why the Earth has dry land that we build upon.

Related Links

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Select the Best Lot With Great Drainage

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CLICK HERE to get FREE & FAST BIDS from local landscapers who can solve your water issues using the advice in this column.

How Much Land Slopes Around My House?

Lots of land can be sloping towards your home. I have a giant mountain just above my house that funnels water towards my home.

What does all this have to do with the water at and around your home? Simple. Topographic maps can be found online. Older topographic maps are sometimes archived and might show what your land looked like before it was developed.

Topo Map NH

This is a topographic map from Google Maps. You just select the Terrain option from the menu to see it. Note the red arrow pointing to the gray line that has the number 800 on it. Any point on that line is 800 feet above sea level as the number. The magenta arrow points to where my house is. The land slopes quite a bit towards Lake Winnisquam. 2017 Copyright Google, Inc. ALL RIGHTS RESERVED

Your builder, or possibly the subdivision developer, undoubtedly moved dirt on your lot to prepare it for building your home. This process disturbed the natural slope of your lot as virtually no undisturbed land is perfectly flat.

What Causes Natural Water Drainage and Slope?

Natural erosion causes all land to have some natural fall or slope. You don't see water drainage issues on most land you walk across because it naturally slopes so water heads to a creek, stream or river.

When you do encounter marshy land, it's because of some temporary geomorphological process.

Lakes are a great example. You can find marshes next to lakes. Lakes are temporary geological features. Mother Nature is constantly trying to fill lakes in.

Is Adding Soil to Low Spots a Good Idea?

Adding soil to the low spots is usually not a good method to fix poor drainage problems. There's a much better way to dry the soil. Ponding water on your lot tells me that you don't have low-slope culverts surrounding your house like a moat surrounds a castle.

These depressions, or culverts, should have been created by the builder so surface water always flows around your house to the towards the lowest spot of land on your lot.

To provide great drainage around your home, you should always have the ground slope away from your home. The building code used to require that the ground should have 6 inches of fall in the first 10 feet of horizontal run away from your home. That can be confusing to some.

grade level

I made this drawing. You can see the foundation wall with a typical sill plate and floor joist. The red line is the lot before the excavator shows up. The top of the foundation should end up 18 inches ABOVE the red line. Use the dirt from the hole to create the slope away from the foundation. (C) Copyright 2017 Tim Carter ALL RIGHTS RESERVED

All it means is that within 10 feet of your foundation, the ground should slope at least 6 inches. This change in elevation could happen within a foot, meaning it would be a very visible slope very close to your foundation walls.

Can You Create a Sloped Swale Around Your Entire Home?

Yes, you can create a water drainage channel or swale around your home.

The builder should have then created an artificial channel around and away from your home that also has a slope to it. The water flowing away from your foundation would enter this channel and then flow, by gravity, completely around your home.

There should never be any ponding in this shallow channel. To achieve great water drainage, a slope of at least 1/8 inch per foot is required. More slope is better if you can tolerate it on your lot.

CLICK HERE to get FREE & FAST BIDS from local landscapers who can solve your water issues using the advice in this column.

Can You Capture Subsurface Water?

Subsurface water can be captured using a perforated pipe in a trench.

french drain pipe

Cross-section of a Linear French Drain including the all-important perforated french drain pipe. Copyright 2017 Tim Carter ALL RIGHTS RESERVED - Do NOT COPY this graphic.

Surface water is but one challenge around your home. You also need to deal with subsurface water that flows through the soil towards your foundation and crawlspace walls.

You can capture and divert this subsurface water by digging a narrow trench in the center of the artificial channel around your home. The trench contains a perforated pipe that collects and diverts the water away from your home.

In the center of this gravel is a linear french drain. Some call them trench drains as I dug a trench and put in a perforated pipe. This area never has standing water in it now. Copyright 2017 Tim Carter ALL RIGHTS RESERVED

How Deep and Wide Should the Linear French Drain Be?

The linear french drain should be about 2 feet deep and 6 inches wide. The bottom of the trench should be parallel with the top of the artificial channel until it gets around your home.

The trench extends past your home towards the lowest point of your lot. The pipe slope can be reduced when the pipe passes the house. The pipe eventually pops out of the ground.

If you do this job, you're creating a linear french drain. They are extremely effective at solving water drainage issues because they intercept the water flowing through the soil. The water is channeled away from the house after it enters the perforated pipe.

Are There Step-by-Step Instructions to Install a Linear French Drain?

Do you want a step-by-step procedure on installing a Linear French Drain? Tim's Linear French Drain Video Series DVD shows you how to keep your basement and crawl spaces dry or on the image below to order Tim's DVD.

Linear French Drain DVD

This DVD shows how to install a linear french drain.  Tim Carter installed this drain on the side of the shed you see in the photos above. You'll feel like you were part of the project now that you read the column above.


What Kind of Gravel Should be in the Trench?

You install a 1-inch layer of rounded or slightly angular gravel that's the size of large acorns into the bottom of the trench.

Trench Gravel

This is perfect gravel to put in the trench for great water drainage. Note there's NO SAND. The water can move fast through the large voids around each stone. Copyright 2018 Tim Carter

Gravel is laid on the perforated drain pipe. The entire trench is then filled with the rounded gravel. This system readily collects subsurface water before it attacks your home. Water will flow from the end of the drainpipe where it eventually breaks through the surface of the ground.

In conclusion, you can easily improve the water drainage around your home using a combination of sloped soil and simple linear french drains. You should install the linear french drains after the final grading is completed.  Be sure to do it before the grass seed is sown.

CLICK HERE to get FREE & FAST BIDS from local landscapers who can solve your water issues using the advice in this column.

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Water Drainage - How To Vacuum Water From Soil For Free
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Water Drainage - How To Vacuum Water From Soil For Free
Water drainage starts with sloped soil around your home. You can dry out wet soil with a linear french drain. Great videos here.
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15 Responses to Water Drainage Tips

  1. Useing the perforated. pipes do you put the holes on the bottom or top. In a heated discussion about this I say holes on top need an expert to get an answer.

    • You're wrong. Holes on the bottom. Your way the water has to build up nearly FOUR inches to get into the pipe! Plus, rounded gravel can easily CHOKE / CLOG the holes when the trench is backfilled.

  2. Dear Tim; Thank you for your. Quick response and I will have to admit to my husband those awful dreaded words, I was wrong, I sure do hate to eat crow lol again thanks. I definitely will use your website again.

  3. Hi Tim, when you say there needs to be a slope of 6" over 10ft, does that slope need to be soil only or can I use rock? In my case, there is a rock bed that extends two feet out from my house, which then turns to grass, but there is hardly any slope to any of it. So, I was hoping to add rock on top of the existing rock to create the recommended slope in the first two feet. I feel like that is too easy to be right, but am not sure! Thank you!

    • Janet, the rock doesn't count especially if water runs right through it and disappears! Grade refers to SOIL. The soil needs to slope DOWN a minimum of 6 inches in the first 10 feet away from your home. Most houses do NOT meet this requirement to their detriment.

  4. Hi Tim, thanks so much for the quick reply! That was the answer I was afraid of, but I wanted to know for sure before I went to all the extra work. 🙂 thanks again. Great website!

  5. Hi Tim,

    I need advice building a storm drain system. I'm going to dig a trench and run PVC alongside of a long exterior wall where three downspouts deposit water at different points. I will connect those downspouts to the buried piping which will lead to a dry well away from the house. My question is this: if I'm afraid of non-downspout water (so, just rainfall) pooling in the same area, would it make sense to make that piping perforated and backfill with gravel in order to make a French drain? Or would that defeat the purpose of having the pipes serve as a channel to the dry well for the downspout water (would it would exit through the perforations rather than continue to the dry well)?

  6. Hi Tim. Love all the information from the blog. Very informative. Question in regards to external sump pump. We are building in area that has high water table. The builder has advised that we should install an external sump with a French drain before he starts on the footings and then the weeping tile would be installed after that. This is what he had to do with another home in the area after lengthy delays because of the groundwater and rain this spring. It seems a little redundant to me. I can see how it would help them dry out the area to do footings etc but not sure long term if that's something that's required. The French drain/external sump is apparently my cost and a significant one at that. Any insight would be appreciated. Jeremy

  7. Tim
    I want to ask the expert.
    I am digging a 300 foot french drain along my driveway perpendicular to the slope of the hilll. (1 foot across and 2 feet deep) and wanted to know the best pipe to use in NY State (Southern Dutchess County. I have a lot of clay.
    I read about the SDR 35 and liked it until a supplier told me it gets brittle in the cold. He recommended strongly the double walled ADS -N12 pipe 4 inch. He said it is stronger and it is not brittle in the cold. He sells both. I feel the only problem is the slits seam to be all around the pipe and it may drop water from a high spot and deposit it on a low spot.
    I want to wrap the pipe in a liner to keep the fines out of he gravel maybe the fabric may get clogged and I should go with gravel on the bottom and sides and put fabric only on the top. I was also considering lining the bottom with plastic so water would not penetrate into the clay soil.
    What is the best pipe to use, and the best drench design.

  8. Just saw your Q&A in the WP advocating the trench drain. Our front yard has barely any slope until about 15 ft from the house then it drops 5 feet to the street. If we installed the trench drain near the foundation could it be covered with soil or mulch or would that just clog it up?

    • MDL,

      Before you go do any amount of work, getting my DVD would be your best bet. I explain in great detail where the trench drain should be in relation to the side of the foundation.

      I urge you to re-read my column above about how the drain is installed, the gravel, and how it looks at the surface.

  9. Hi Tim,

    I'm wanting to install a drainage system that would move the water from my downspouts away from my foundation. I am wanting to run the drainage via a trench under my landscaping with a pop up connector at the end. My question is, how far do I need to run the pipe for it to drain properly. I was under the impression that due to the entry point of the water being the top of the guttering system, that it would still drain fairly well with minimum slope. My yard is relatively flat util you get to the very end (50 ft), and I"d like to minimize the amount of trenching needed.

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