Clean water in
Sand & Carbon Filters
Particles out with sand. Chlorine, odour and colour out with carbon.
Most treatment trains start here. A multigrade sand filter catches what you can see — silt, sediment, the cloudiness in tanker and borewell water. An activated carbon filter after it takes out what you can smell and taste.
What it means
A multigrade (pressure sand) filter is a vessel packed with layers of graded media — fine at the top, coarser below, gravel at the bottom. Water is pushed down through it and particles are trapped in the bed.
Activated carbon works differently. Its granules are full of microscopic pores with an enormous surface area, and dissolved substances — chlorine, many organic compounds, the things behind odour and colour — stick to that surface. This is adsorption, not straining.
Together they protect everything downstream: a softener’s resin and an RO’s membranes both last longer when silt and chlorine never reach them.
How it works
Step by step, as drawn in the diagram above.
- 1
Raw water into the sand filter
Water enters at the top and spreads over the media bed.
- 2
Particles stay in the bed
Passing down through the graded layers, silt and suspended solids are caught; filtered water collects at the bottom.
- 3
Through the carbon filter
The clear water goes through the activated carbon bed, where chlorine, odour, colour and organics are adsorbed.
- 4
Filtered water out
Clear, odour-free water goes on to storage, a softener or an RO.
Backwashing
As the bed fills with dirt the pressure drop across it rises. A backwash cleans it in place.
- 1 Service Water flows down through the bed, filtering.
- 2 Backwash Flow reverses upward, lifting and loosening the bed so trapped dirt washes out to drain.
- 3 Rinse A short downward rinse resettles the bed before it goes back into service.
What it takes out
- Silt, sediment and turbidity (sand)
- Suspended solids and oxidised iron (sand)
- Chlorine and chloramines (carbon)
- Odour, colour and many organic compounds (carbon)
What it does not
- Hardness — calcium and magnesium
- Total dissolved solids
- Dissolved salts
- Bacteria are not reliably removed
Where it is used
- First stage on borewell and tanker water
- Ahead of softeners and RO plants
- Apartments and townships
- Swimming pools
- Process water pre-treatment
What we size it on
- Flow rate the building or process needs
- Turbidity and suspended solids in the raw water
- Chlorine or organics to remove (carbon)
- Water and pressure available for backwashing
Looking after it
- Backwash on schedule, or when pressure drop rises
- Watch the pressure gauges either side of the filter
- Replace carbon when it stops removing chlorine and odour
- Top up or replace sand media as it wears over the years
Questions, answered
Do I need both a sand and a carbon filter? ＋
Not always. Sand handles particles; carbon handles chlorine, odour and colour. If your water is cloudy but odour-free, sand may be enough; municipal water with chlorine, or water with a smell, needs carbon too.
Will these filters soften water? ＋
No. Hardness is dissolved calcium and magnesium, which passes straight through sand and carbon. A softener removes it.
Why does carbon go before an RO? ＋
Chlorine damages most RO membranes. A carbon filter removes it first, so the membranes last.
The rest of the treatment train
Clean water in
Water Softeners
Hardness out. Scale, white spots and failing geysers with it.
Clean water in
Ultrafiltration (UF)
Particles and microbes out. Minerals stay in.
Clean water in
Industrial RO Skid Systems
Dissolved salts out — the one thing no filter can touch.
Clean water out
Sewage Treatment Plants (STP)
A building’s sewage, treated well enough to use again.
Clean water out
Effluent Treatment Plants (ETP)
Industrial effluent, treated to meet discharge or reuse norms.
Send us your water report
Or tell us where your water comes from — we design the treatment train, install it and stand behind it.