Home › Guides › FRP media filters
Backwashing Sand, Multimedia and Carbon Filters
- Reverse flow lifts the bed and flushes dirt
- Backwash on pressure rise or schedule
- Backwash → rinse → service
- Media wears out: top up or replace when needed
On this page
Why Backwash?
As water passes down through the media, dirt fills the spaces. Pressure loss rises and flow drops. Backwashing cleans the bed so it filters well again.
When to Backwash
- The pressure difference between inlet and outlet gauges has risen noticeably above its clean level (installers often use a set rise as the trigger: ask yours).
- Flow has dropped.
- On the schedule set for your water (dirty water needs more frequent backwashing).
Manual Multiport Valve: Step by Step
- Switch off the pump before moving the valve handle.
- Set the valve to Backwash and start the pump. Run until the water in the drain sight glass or outlet looks clear.
- Stop the pump; set to Rinse. Run briefly to settle the bed and clear dirty water from the outlet.
- Stop the pump; return to Service (Filter) and restart.
Automatic valves run these steps on a timer: manual vs automatic valves.
FRP Filter Vessels
| Product | Price |
|---|---|
| 817 FRP Tanks and PP Filters | KSh 9,200 |
| 820 FRP Tanks and PP Filters | KSh 9,800 |
| 835 FRP Tanks and PP Filters | KSh 11,600 |
| 844 FRP Tanks and PP Filters | KSh 12,800 |
| 948 FRP Tanks and PP Filters | KSh 13,500 |
| 1054 FRP Tanks and PP Filters | KSh 15,000 |
| 1248 FRP Tanks and PP Filters | KSh 22,500 |
| 1265 FRP Tanks and PP Filters | KSh 25,000 |
| 1465 FRP Tank and PP Filter | KSh 36,000 |
| 1665 FRP Tank and PP Filters | KSh 43,000 |
Current listed prices incl. VAT (updated 4 October 2026).
Sizes explained: FRP tank sizes.
Media Life
Sand and multimedia slowly wear and clump; carbon gets used up. Top up or replace media when backwashing no longer restores performance or water quality, or on your installer's schedule.
Frequently asked questions
What is backwashing a filter?
Reversing the flow through the filter bed so dirt is lifted and flushed to drain.
How often should I backwash a sand filter?
When the pressure difference rises or flow drops, or on the schedule set for your water.
What is the rinse step for?
It settles the bed and clears dirty water before the filter goes back into service.
Do I switch off the pump before changing the valve?
Yes, always stop the pump before moving a multiport valve handle.