Methods of Soil Drainage

It is better to lay drains in the direction of the greatest slope, rather than across it obliquely.

There are three types of drains: main drains, submains and small drains.

All of the other drains send their water to the main drains.

The mains lead all of the water to their point of outfall, which should be in the lowest part of field.

Submains are laid along secondary low places. Normally, they enter into the mains. However, if the field is extremely uneven, they may have a separate outfall.

Small drains should enter the larger pipes at angle. If they meet the larger pipes at a square angle, the pipes may become clogged with silt.

Where two pipes must be joined together, a hole should be made through the larger one. The lip of the smaller pipe should go through the larger pipe so that the top of each pipe is level. Broken tile shouldcover the space where the pipes are joined so that soil and silt does not enter the pipes.

Field drains should not be longer than 250 yards. If necessary, they should be broken up by other mains or by submains.

There should be at least one main outlet out of which all of the drains can empty.

It is easier to take care of one main drain outlet than many small ones. It is important to make sure that drains are kept clear.

4 to 6 inch pipes are usually used for mains, 3 inch pipes for submains and 2 inch pipes for small drains.

If there is only a slight fall, larger pipes should be used.

In clay, a drain should have a fall of 1 in 100 for the mains and 1 in 75 for small drains.

The fall should be greater if the soil is lighter.

Drains in stiff clays should be 2 to 2 ½ feet deep and 15 feet apart, or closer.

If the soil is porous, they should be 3 to 3 ½ feet deep and 20 feet apart.

In deep, peaty soils, pipes should be larger than commonly used. They should be from 5 to 6 feet deep and about 30 feet apart.

When cutting trenches, begin at the outfall. This should be at least 6 inches higher than the lowest part of the ditch, to allow room for silt to be deposited.

The bottom of the trench should be just wide enough to fit the pipes easily.

If it is too wide in any place, stones, pieces of broken pipe or clay lumps can be used to hold the pipes in position.

Try to keep drainpipes away from plant roots so that they do not block the popes.

Some drainpipes are made of porous concrete and can be used to prevent roots from entering.