Sand Filter Pre-Coat
The oldest and most popular method of filtration is sand. Sand filters share two things in common:
- When in the filtration mode, water always flows from top to bottom
- They all have some sort of lateral or under-drain with slots to hold back sand while allowing clean, filtered water to pass through
High-rate sand filters use a special filter sand, normally .45 to .55mm (also known as pool grade #20 silica sand), because it has sharp edges that serve to separate particles, allowing filtration to take place. They operate on the basis of "depth" filtration; dirt is driven through the sand bed and trapped in the minute spaces between the particles of sand. Initially, a clean sand bed will remove larger particles, and then, as the bed starts to load up with dirt, it will remove finer particles.
How "SAND-KOTE" Works
Davies "SAND-KOTE" pre-coats the sand bed, removing smaller particles than can be removed by sand alone, including body oils and suntan lotions. Davies "SAND-KOTE" gives faster pool water clean-up after a shut down of pool. Davies "SAND-KOTE" backwashes out easily, and will not affect pH of pool water.
Davies "SAND-KOTE" does not affect the chemical balance of your pool or add anything to the water...it simply keeps it much cleaner and, at backwash time, can be readily flushed out prior to new application.
The addition of Davies "SAND-KOTE" does not require any special tools or modification to existing systems. It is added to the filter through the skimmer. Without Davies "SAND-KOTE" your filter is operating far below its potential capacity.
Because Davies "SAND-KOTE" removes smaller particles than sand does alone, the first several times it is used, it will require backwash earlier than normal. However, after this initial clean-up period, Davies "SAND-KOTE" will extend filter cycle, (time between filter backwash) by as much as 70%. This pre-coat is removed (along with the filtered contaminants) with the backwash, and new Davies "SAND-KOTE" must be added--see chart below.
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