Tetra LP Block® Underdrains for Drinking Water Filters

Tetra LP Block is world leader in the design and manufacture of dual underdrains for drinking water filters, with more
than 70 years of experience. Their main attributes are:

  • Less civil works
  • Quick and easy installation
  • No losing of filtering media
  • Excellent conditions for water or air-water backwash
  • A solution to maintenance problems. Service life of over 30 years.

Dual Parallel Underdrains are installed directly at the bottom of the filter bearing the media of the filters and its support. They collect the filtered water and distribute evenly backwash water and air.
In these systems, backwash air or water is distributed by main channel and after by two secondary or compensation channels. This promotes an optimal distribution with a minimum charge loss.  Building material is HDPE.

At the bottom it has a high distribution of holes 236 holes/m2. This produces a better wash of the filter media leaving no dirty volume that in time will be a loss of the media (dead spaces) or decreasing filtering efficiency.


From the installation perspective, differences are very important when compared to the conventional nozzles system. Here there is no need of building a concrete flat bottom either in block or with tiles. With Tetra LP Block®  setup times are considerably reduced as well as work force, because they are installed at the bottom of the filter.

Civil works are also considerably diminished because the height of the flat bottom is reduced thanks to dual lead of Tetra LP Block®.   Traditional nozzles need at least 75 cm to generate uniform backwash conditions. With Tetra LP Block® ideal  backwash solution is reached with just 30 cm.



All in all, the adventages of operating your water plant with TAERSA filters with Tetra LP Block® equipment are the following:

  • Less civil works
  • Less setup times
  • Optimal hidraulic profile
  • Gravel use can be avoided
  • Services life of at least 20 years with no maintenance
  • HDPE is resistant to rust and chemicals
  • Larger and better filtered water quality, resulting from longer filtration runs.