Pre filters

The prefilter is designed to trap matters in suspension.
This device is also known as clogging indicator. It is located at the output of a liquefier (all-water tank, septic tank or
decanter digester) and before an underground spreading system or a drained filter bed.
We recommend to use our pre filters following the cases below :

DEC1050 - Liquefier 1000 to 1500 l
DEC2/0201 - Liquefier 2000 l
DEC1100 - Liquefier 3000 l
DEC2/0501 - Liquefier 4000 to 5000 l
The pre filter is useful after being filled with pozzolana and other filter materials.
It has a « fuse » role in case of malfunction or in case of a lack of maintenance of the all-water tank or the decanter
digester. In this case, matters in suspension go out of the tank or the decanter and these matters are trapped by the filter materials located in the pre filter.
The role of the pre filter is very important, it prevents from the clogging of the spreading installations, the drained
filter beds or infiltration wells.
The device will be buried outside a building and must be installed on a perfect level.
It will be buried in a zone protected from vehicles passing.
The covers will be level with the finished ground and will remain accessible. The bottom of the hole must be perfectly flat and covered with 10 cm of sand. The backfill must be made using sand only, never stone or gravel.
The device must be filled with pozzolana or other filter materials (regular graining between 10 and 50 mm) and will be done before or at the same time that the infilling.
If vehicles will pass over the area or if the cover won't be level with the finished ground, a concrete slab must be poured resting on stable ground and equipped with a manhole cover. This concrete slab should be withstand the strains imposed.
This notice only applies for stabilized, non-flooded grounds and those without ground water. For all other cases, please contact our research department.
Check periodically the filter materials. In case of clogging, extract them from the device, clean with a water jet and
replace them.
If the cloggings increase, check if it is necessary to carry out draining or maintain the tank or the decanter. Otherwise,
filter materials should be changed (on average, every 2 years).


RH2/4031 -