Changing the filter media: when to do it and how to go about it
Filter media (sand or glass) does not last forever: reckon on about 5 years for sand, 8 for glass. But age is only a marker — as long as the water stays clear and filtration holds up, there is no rush. You replace it when the signs of wear appear, and it is quite doable yourself.
In short
Ageing filter media clogs, packs down and lets water take “preferential paths” through it without really filtering. The result: water that stays cloudy despite correct chemistry, backwashes that come ever more often, and pressure that climbs quickly on the gauge. If you tick those boxes, it is time to change the media. The job mainly needs a wet/dry vacuum and a bit of elbow grease — no professional required.
Do you really need to change it?
Reaching 5 years (sand) or 8 years (glass) does not mean “replace right now”. It is a reminder. As long as your water is clear and filtration holds without endless backwashes, keep your media. Replace it, though, if you notice several of these signs:
- Water stays cloudy despite correct pH and chlorine and enough filtration.
- Frequent backwashes: you have to clean the filter more and more often.
- Pressure climbs quickly after a wash: the media is clogging (it packs down and “channels”).
What you need
The most useful tool is a wet/dry vacuum to remove the old media. Have the new media ready at the right volume and grain size (marked on the filter), and a mask: sand gives off a silica dust best not breathed in.
Access tip: if the diffuser or laterals do not come apart and get in the way of the vacuum, tape a length of garden hose to the end of the vacuum: you can then reach the bottom of the tank and the awkward spots without forcing anything.
After replacing
A backwash then a rinse are essential to flush the fine dust from the new media before returning to filtration. Note the year of the change: it is your marker for the next due date.
What to do, step by step
Switch off the pump and isolate the filter
Stop the filtration. Close the suction and return valves if you have them, and release the pressure (drain plug or air bleed).
Open the filter
Remove the multiport valve (or the lid). Locate the central tube and the laterals so you do not damage them while emptying.
Vacuum out the old media
With the wet/dry vacuum, remove all the old sand or glass. If the diffuser blocks access, tape a length of garden hose to the end of the vacuum to reach the bottom and the corners.
Pour in the new media
Protect the central tube (a little water in the bottom cushions the fall), then pour the new media to the volume marked on the filter. Do not exceed the line: the media needs room to expand during a wash.
Reassemble and backwash
Refit the valve and its seal. Run a backwash, then a rinse, to flush the fines from the new media.
Return to filtration
Set the valve back to “Filter” and restart the pump. Check for leaks, and note the year of the change.
Frequently asked questions
How often should filter media be changed?
About every 5 years for sand and 8 years for glass, as a guide. It is not a hard deadline: as long as the water stays clear and filtration is effective, you can keep it longer.
Can I replace sand with glass?
Yes, filter glass goes into the same sand filter. It filters a little finer, clogs less and lasts longer. Respect the stated volume (glass is slightly less dense than sand).
How do I empty the media without dismantling everything?
A wet/dry vacuum does most of the work. If the diffuser will not come apart, tape a length of garden hose to the end of the vacuum to reach the bottom of the tank.