Swimming Pool Sand Filter Maintenance and Repair
All sand filters work the same way, i.e. pool water is fed from top to fall onto the sand medium, and then allowed to percolate through to the bottom of the medium where the laterals are located to collect the filtered water. Sand filter can trap particles of 15 to 30 microns; and some commercial products claim that its products can enhance the filter to trap particles as small as 5 microns.
Sand filters may either be available custom-fabricated ( in a large steel tanks) or off-the shelf ( in fiberglass tanks)
The media are silica sand or crushed anthracite. Filter may be single, dual or multi-media.
Multi-media filters have 450nm of anthracite (1.0 – 1.5 mm), 200 mm silica sand (0.5 mm), 100mm (0.2-0.4 mm) silica sand and garnet. It can handle higher flow rates, give deeper penetration and longer filter runs compared with single or dual media types.
To effectively filter water, the ideal situation would be to have the large grains of media at the top to trap the large solids and uniformly decreasing grain size in the direction of fluid flow with the small grains at the bottom to do final polishing. The penetration of the solids through the entire bed allows increased solids storage, longer filter runs and higher filtration rates.
How does sand filter work:
Soil is captured in the filter bed by a combination of 2 processes:
- Gelatinous and mucous-like substances and oils tend to cling to the grains of filter sand and
- Solids particles lodged in extremely small spaces and voids between the sand particles.