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Every owner freely disposes of the waters he receives, but he must not discharge them to his neighbor. In the absence of a rainwater system of sewerage, it must ensure infiltration. Also called infiltration well or filter well, the sump allows this dispersion of rainwater in the soil. It should only be used as a drainage device for rainwater drainage. It should only be considered if the sewage system does not include a specific rainwater drainage system.

Necessary material

  • Excavator (or micro-excavator)
  • Masonry material

Principle of operation

A system only for rainwater
The sump should only receive rainwater. It is strictly forbidden to evacuate effluent. You must be aware of the risks of pollution that they could generate on groundwater. The use of this type of installation for the purpose of sewage treatment is therefore strictly forbidden by the water law, on pain of a contravention.

The dispersion
The classic solution is to dig a well in which we place a big perforated nozzle. The base of the well must be more than 1 m from a potential water table. It is in the upper part of the well that the arrival pipe of collected rainwater flows, generally on the roof. Infiltration runoff from the surface must be able to penetrate directly into the well. If the well is closed on the surface, it must have ventilation holes.

Two methods to implement a sump

The simplified method
It consists of stack blocks in a well, with or without pebbles. We just close the well with a layer of gravel and with topsoil on the surface. This solution approaches the absorbent tray of a septic tank.

If the nature of the soil allows, the well can be dug by hand.

Digging the sump.

  • A well from 1.50 m to 2 m must be dug by hand or with a micro-backhoe, which can be easily rented.

Stacked, breeze blocks facilitate the infiltration of water into the soil.

Stacking of blocks.

  • Breeze blocks must be stacked around the well to prevent it from filling.

A perforated PVC or cement nozzle is placed in the center of the well.

Installation of a perforated nozzle.

  • The implantation of a perforated nozzle in the center of the well favors the infiltration of water.

Piercing in the center of the well.

Setting up stones.

  • Rock is thrown into the center of the well.

The well is filled with gravel and then soil before planting sod.

Re-grouting on gravel.

  • Rebouching with gravel. A gravel bed will promote the absorption of water at the surface of the well.
  • A layer of topsoil will melt it in a lawn after sowing sod.

The closed sump
This method consists of close the sump with a concrete slab and visit look. The surface infiltration is not targeted, we just fill the block with staggered blocks.

The digging of the well is done by hand or with a machine.

Digging the sump.

  • This type of well generally has dimensions larger than those of a simplified sump.

This type of sump is filled with blocks, in addition to two layers, staggered.

Stacking of blocks.

  • Several layers of blocks, stacked in staggered rows, fill the sump.

The sump is closed by a concrete slab with, in its center, a look of visit.

Realization of a slab with central look.

  • A concrete slab, with a central look, closes the sump.

The slab of this sump is equipped with a central inspection cover.

Laying the cover of gaze.

  • A cover of gaze closes the slab of this sump.

(photos / visuals: © DYI-Prod, except special mention)

On the same topic

  • DIY tips
    • Rainwater: promote their flow and recover
    • How to evacuate and recover rainwater
    • Recover rainwater
    • Evacuation of rainwater (gutter)
  • Questions answers
    • How to recover water for the garden and the house?
    • Regulation of rainwater runoff
    • Rainwater drainage
    • Where can I find a quote for the installation of a rainwater recuperator?
    • Drainage of a land

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