How to design a French
drain and drywell
drainage system
Step 2

Designing a French Drain and Drywell
System for Lawn, Yard, and Garden
Step 2

Please first read Step 1: Lawn and Garden Drainage Guide

In Step 2 you will find information on:

• How to design and build an affordable drainage system
• French drain and drywell tips for your lawn
• Installation of plastic pipe and drainage tile
• Connected landscape drainage system guide

How To Design a Drainage System – Step Two

This section will describe both how to design your water drainage system, and maybe
how to avoid have to install one at all. Gather your sketch and notes and let’s get
started.

Look at your notes from Step One -
How To Discover Your Water Drainage Problems
– to see how long it took the different areas of standing water to disappear and to
decide which situation below fits your lawn or garden drainage issue. The links below
will take you to specific design and installation information.

If the standing water disappeared in an hour or so - then your lawn, yard, and garden
has decent drainage and all you may need to do is
fix your Lake Downspout (gutter)
problems.

If there were no Rainy Rivers, or they disappeared quickly, or ran in an area that is
not a problem –
then you can probably just improve the yard top soil drainage, or
perhaps
install a French drain or build a drywell to drain your Soggy Lawn Swamp,
along with
fixing any gutter downspout drainage problems of course.

If you have any rain water collecting up next to your foundation – then you will need to
correct the slope of the ground next to your foundation first.

If your drainage problems do not fit in the above categories, or fit into multiple
categories –
then you will have to design and install a connected drainage system
utilizing the information below as well as our other
installation instructions.

Below are important drain system design guide lines, rules, and information:

Foundation drainage and downspout issues are critical
A soggy lawn is annoying, but a flooded basement or crawlspace is expensive and
potentially destructive. Always fix foundation and gutter drainage issues first.

Keep your water on your own property if at all possible
Draining your excess water away to the street or a ditch seems like a simple solution,
but it just transfers your problem to others. Also your lawn, trees, and plants will be
healthier if you have created a store of rain water in the subsoil for your plants to
access in dry times. Only after all other options to improve your drainage and keep the
water in your own soil should you send the excess off-site.

Top soil can be made to drain better by adding amenments
If your top soil is mostly clay, or is very compacted, your drainage will be greatly
improved by amending the soil with compost, gypsum, or other organic matter and
mixing it in by hand or with a rototiller. In some cases, you may be able to top dress a
nice lawn with sand to improve drainage rather than tilling up your yard.

Garden drainage issues by can also be fixed by raising the plants
Installing a drainage system in a garden might cause the soil to become too dry or
interfere with digging or cultivating. It is also possible to keep you plants from drowning
by using raised beds to rise above the occasional soggy situation.

Water will flow along the path of least resistance
Water flows downhill, not uphill. Water will flow through loose gravel easier than
through tight soil. Water will flow through a pipe easier that through gravel or soil.
Drainage is improved when water can easily flow from very soggy areas to drier areas.

Water can flow into, out of, or through plastic drain pipe or tile
Remember that there are two types of drain pipe: perforated and solid. Perforated
pipe has many little holes punched or drilled into it to allow water to enter and exit the
pipe. In any drainage system design there is often water flowing IN through the
perforations in a soggy area at the same time there is water flowing OUT of the
perforations in a drier area. The perforations always go on the bottom. Solid pipe is
used in a drainage system to carry water PAST areas where you do not want to add
more water. Most drainage systems use both types of pipe or tile.

A French drain is simply a trench full of gravel that moves water horizontally
It acts much like a perforated pipe in that it collects water from a soggy area and
distributes water to drier areas. French drainage systems often contain one or more
pipes buried in the gravel trench.

A drywell quickly moves water deeper into the subsoil.
The purpose of a drywell is to allow water to enter the subsoil faster and easier. It is
simply a hole dug downward into the subsoil and filled with gravel or a sleeve. A small
drywell can be dug with a posthole digger. A large drywell may use a precast concrete
cylinder as a sleeve.

Designing a drainage system is a little complex, but fortunately most of the knowledge
and techniques are fairly simple. Please read ALL of the above linked sections before
going on to Step Three -
How To Diagram and Layout a Yard Drainage System
Lawn and Garden
Drainage Guide

Step 1
Step 2
Step 3
Step 4
Instructions
Lawn Yard and Garden tools
trenching for a French drain
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