How to build a dry well

A dry well is not a septic tank, this is the first distinction that needs to be alluded to.

stormwater drainage

What is a dry well

A dry well is a pit that is filled with a cistern, of various materials, without bottom, whose purpose is to absorb the clear water discharges that are made to percolate inside the dry well by means of a special pipe.

In short, a large hole well built in such a way as to disperse the excess water in the surrounding soil and prevent it from flooding on the surface.

In some circumstances, especially in rural dwellings, there is no possibility of conveying the drainage channels towards a sewer or towards a slope that can drain the water naturally.

In these cases it can be useful, if not indispensable, to build a dry well in order to collect the water and then let it filter, slowly, into the ground.

In this way, even the rainwater, which from the roof is conveyed by the gutters to the downspouts, finds its final destination.

Part of the water of meteoric origin could be usefully collected and reused after being channeled into special water collection tanks, above ground or underground.

The excess, however, will still have to disperse into the ground, and if the soil is not able to absorb it here is that the dry well will come to our aid.

Do it yourself a small dry well

Before building a dry well it is always good to contact the competent municipal offices to know the rules and understand if there may be problems with the permeability of the soil and the level of the water table.

Building a small dry well, sufficient to drain an area of about 20 square meters, you can also do it by yourself, using a shovel and a pickaxe and a lot of hard graft.

type of dry well

To make it, a metal or plastic barrel with a capacity of 200 liters is sufficient.

For a larger dry well, in concrete, it is instead advisable to contact a specialized company that will take care of the installation.

The first thing to do, if you use a metal barrel, is to remove the upper and lower parts.

To do this, it is necessary to use an angle grinder with a special disc for cutting metal.

Remember to always work safely by wearing all necessary personal protective equipment.

An underground metal barrel will inevitably oxidize.

If you cannot use a plastic tank, therefore, the advice is to apply a coat of tar both inside and outside the barrel to protect it from corrosion.

Where to put the dry well

The choice of where to place the dry well is not at all secondary and also depends on the lay of the land.

The dry well (or wells) should be located at least 4-5 meters from the downpipe and in an area lower than the house, where possible.

I have spoken of wells, in the plural, because, at least on a theoretical level, it would be better to have more than one, each fed by a distribution well.

This, on the one hand, multiplies the work but, on the other hand, allows for the construction of smaller and more independent dry wells.

In any case, on a rocky terrain it can be extremely difficult to dig a large hole about 1.5 meters deep without using a mini excavator, for example.

Preparing the tank to be buried underground

I wrote above that tanks can be made of metal, plastic or masonry.

In the case of a do-it-yourself dry well, once both the bottom and the top of the bin have been removed, it will be necessary to make holes at regular intervals all over the surface of the bin.

Finally, the hole of the appropriate diameter must be made, where the drainage pipe will enter.

Sizing of the drain well

Once the right position in the garden has been found, the first thing to do is to remove the superficial grass layer for a diameter of 2 meters.

Then you can start digging, by hand or by mechanical means, until you reach a depth of 1.5 meters.

At the end we should have a cylindrical shaped hole on the bottom of which we will place a layer of 5-10 centimeters of stones.

At this point we can place the barrel in the center of the excavation and connect the drainage pipe.

Dry Well filling

The next step is to fill the barrel with rather coarse crushed stone, together with brick fragments and river stones having a diameter from 1 to 15 centimeters.

Now it's the turn of the metallic net, galvanized or in plastic material, that will have to surround the drum, leaving a free space of about 20 centimeters that will have to be in turn filled with rubble.

building a dry well

The mesh of the net should be quite fine, 0.6 to 1 centimeter. The two ends of the net should be closed with wire.

We are now ready to complete the work: in the gap between the net and the bin pour some crushed stone and gravel and, for each layer, fill also with earth the area outside the net.

This procedure ensures that the net does not open due to the thrust of the stones, making all the previous work in vain.

The upper part, to complete the closure, will be filled with a layer of gravel and at least 30 centimeters of earth and then, after everything has settled, it will be possible to relocate the turf or sow the part with the same essence sown in the garden.

dry well filling

DIY Editor
Do-it-yourself enthusiast. I started with the renovation of my flat and then I changhed this passion into my job.