Principles Of Operation - Astralpool CLARITY Manuel D'installation

This manual has been specially written to guide the installer of filter as well as any person responsible
for its maintenance. Following the recommendations hereby stated, whitch are a result from a long
work experience about filtration systems at Astral company, you will get the best quality and the highest
crystallinity of your pool water.
1. INTRODUCTION
Diatoms are unicellular algaes existing in both fresh and sea water, they are capable of retaining the
silica dissolved into water. After they die, their skeletons fossilize becoming a white, light and porous
rock which is called diatomaceous earth. By drying and crushing the rock, diatomaceous earth dust is
obtained wich is used to water filtration. Due to the D.E. Porosity and tiny size, around 0.0036 mm, it is
even possible to filter particles down to 2 microns.

2. PRINCIPLES OF OPERATION

At the inside of the filter there are 8 filtering grids injection molded of plastic and covered by a thin
flexible woven polypropylene cloth, called "septum". After introducing the D.E. Directly into the
skimmer (dissolved into water). They enter the filter from the bottom and gradually distribute all over the
grids making up a thin layer called "filter cake" where dirt from water will be retained. (See Fig.1)
Clean water is taken up by a top mounted grid manifold, then water returns to pool. Even though the
initial head loss on these filters is very low, their great power of filtration make them dirty very easily:
when operating continuously, it is necessary to backwash it in less than 24 hours.
Nevertheless, in this kind of filters a regeneration process occurs that lengthens the time between filter
cleaning.
2.1 The automatic regeneration
The D.E. Keep attached to the septum due to the water pressure. That is the reason why, any time the
filtration pump is turned off, they are released from the septum and fall down to the bottom of the filter. It
is due to the special design of the grids, which shake off the septum when the pressure slops, that the-
highest D.E. Detachment is achieved. That is how we get, at the bottom of the filter, a paste formed by
diatomaceous earth and retained dirt.
When starting the pump, the whole paste is mixed due to the water turbolence, then it goes up to the
grids and makes up a new filter cake which will ready to restart filtration (See Fig.2).
Allhough the principles of operation seem to be simple, there are three fundamental details to which
ASTRAL has paid special attention in order to achieve the highest efficiency from this system:
Highest D.E. Detachment from grids.
Thanks to the special grid shape (curved vertical grids) you achieve as follows : a large filtration area, a
D.E. Uniform distribution all over their area and highest D.E. Detachment when turning the pump off
(see Fig. 3).
D.E. Total profit
One of the main problems form using these filters is that the D.E. Paste is little by little accumulated in
difficult accessible areas and the number of useful filtering D.E. Decrease gradually. Thanks to the
special design of the lower support grid, cone shaped and very small surface, accumulation and loss of
D.E. Is completely avoided. (See Fig.4).
2
ENGLISH