A pool filter is the hardest-working part of any Cape Town backyard pool, quietly trapping leaves, sunscreen, dust and the fine grit that the Cape Doctor blows in all summer. When the filter clogs, your water turns cloudy, your pump strains, and your chlorine simply stops doing its job. The good news is that cleaning your filter is a task most pool owners can handle themselves. This guide walks you through the three filter types you are most likely to have — sand, cartridge and diatomaceous earth (DE) — with practical steps suited to local conditions.
Why Filter Cleaning Matters in Cape Town
Between the summer south-easter carrying fine sand and the winter rains washing debris into open pools, Cape Town filters take a beating year-round. A neglected filter forces the pump to work harder, pushes up electricity costs, and can leave your water green even when your chemical balance looks fine. Regular cleaning also protects the surface of your pool. If you have already invested in marbelite resurfacing or a new lining, keeping the water properly filtered helps that finish last far longer.
How to Tell Your Filter Needs Cleaning
- The pressure gauge reads 8–10 kPa (or roughly 2–3 psi) above its normal clean level.
- Water returning to the pool feels weak or the flow has dropped noticeably.
- The water looks dull or cloudy despite balanced chemistry.
- It has simply been a while — most filters benefit from attention every few weeks in peak season.
Cleaning a Sand Filter
Sand filters are the most common choice on Cape Town properties because they are robust and low-maintenance. They are cleaned by backwashing, which reverses the water flow to flush trapped dirt out to waste.
- Switch off the pump before touching the multiport valve — never move the valve while the pump is running.
- Turn the valve to Backwash and run the pump for about two minutes, or until the sight glass runs clear.
- Switch off again, turn the valve to Rinse, and run for 30–60 seconds to resettle the sand bed.
- Return the valve to Filter and top up the pool, since backwashing sends water to waste.
Sand itself becomes rounded and less effective over several years and should eventually be replaced. If backwashing no longer clears your water, the media may be spent or channelled.
Cleaning a Cartridge Filter
Cartridge filters use a pleated element instead of sand, and they cannot be backwashed. They trap finer particles, which makes them popular for smaller or water-wise pools where saving every litre counts.
- Turn off the pump and release the pressure using the air-relief valve on the filter housing.
- Open the housing, lift out the cartridge, and inspect the pleats for tears.
- Hose it down from the top, working into each pleat to dislodge trapped debris.
- For a deeper clean, soak the cartridge in a filter-cleaning solution overnight, then rinse thoroughly.
- Reassemble, making sure the housing O-ring is seated and lightly lubricated.
Keeping a spare cartridge on hand lets you swap in a clean one instantly while the other dries, so your pool is never left unfiltered during a Cape Town heatwave.
Cleaning a DE Filter
Diatomaceous earth filters offer the finest filtration of all three, coating internal grids with a powder that captures very small particles. They need a little more care but reward you with exceptionally clear water.
- Backwash the filter as you would a sand filter to flush out the old DE powder.
- Once or twice a season, open the filter, remove the grids, and hose them clean.
- Inspect the grids for tears or worn fabric and replace any that are damaged.
- Reassemble, then recharge the filter with the correct amount of fresh DE powder through the skimmer.
Always handle DE powder carefully and avoid breathing it in, wearing a dust mask when adding it.
When to Call in a Professional
Routine cleaning is well within reach for most owners, but some issues point to something deeper. Persistent cloudy water, cracked filter housings, or a pool that will not hold clarity despite a spotless filter can signal problems with the plumbing, the pump, or the pool shell itself. If you are noticing staining or rough patches alongside filtration trouble, it may be time to consider fibreglass pool lining to restore a smooth, easy-to-maintain surface.
A well-maintained filter is the foundation of a healthy pool, but it works best as part of a bigger care routine. If you would like a hand getting your system running properly — or you are planning upgrades for the season ahead — the team at Aquatic Pools is here to help. Feel free to get in touch for advice tailored to your pool and your corner of Cape Town.
