Aluminium based flocculants are excellent. IMHO this is essential for proper water treatment,in order to capture colloids.Originally Posted by 257WbyMag
A sand filter is able to filter about 20 microns - colloids are 0.001 - 0.1 microns .The problem with non commercial filters is the filtration speed , which is usually between 15 - 20 gpm/ft2. If you were to add the flocculant slowly into your skimmer it does not have the time to form a proper floc. Filter channeling will happen and the floc will pass through the filter and finally ending up in the pool.
Now you'll have aluminium residuals in your pool, which may cause itchiness on the skin.
Another method for flocculation in private pools is to broadcast the aluminium sulfate over the pool surface . Turn off your pump, wait till the floc settles at the bottom of the pool and vacuum to waste.