Pool Filter Cleaning in Ontario: Sand vs Cartridge vs DE
Almost every water clarity complaint we attend across the GTA traces back to the filter, not the chemicals. Pool filter cleaning is the single highest-value maintenance task a pool owner performs, and it is also the one most commonly done on the wrong schedule, in the wrong way, or not at all. This guide covers the sand filter vs cartridge filter question honestly, how to backwash without wrecking your valve, when media actually needs replacing, and the Ontario seasonal schedule that keeps water clear without wasting your weekends.
Ryan Roy
Lead Pool Specialist, Swimpool 360
- Written for the Toronto & GTA Market
The One Number That Runs Everything
Forget cleaning schedules based on the calendar. Pool filter maintenance is driven by one number: the pressure gauge on top of your filter tank.
Immediately after a thorough cleaning, with the pump running normally, write down the pressure. That is your clean baseline, and it is specific to your pool, your pump, and your plumbing. It might be 10 PSI, it might be 18. The absolute number does not matter. What matters is the climb.
As the filter traps debris, flow restricts and pressure rises. When the gauge reads 8 to 10 PSI above baseline, it is time to clean. That is the whole rule. Below that, the filter is working well and cleaning early actually reduces performance on sand filters, because a slightly loaded sand bed traps finer particles than a perfectly clean one.
If you do one thing after reading this: write your clean baseline pressure on a strip of tape stuck to the filter tank. Every homeowner we have suggested this to has stopped guessing about filter cleaning within a week, and most stop having clarity problems entirely.
What a falling pressure means
Rising pressure is a dirty filter. Falling pressure is a different and more urgent problem: it means the pump is not getting enough water. Check the water level, the skimmer basket, and the pump basket. A pump starved of water overheats and can destroy its shaft seal in minutes.
Sand vs Cartridge vs DE Compared
The sand filter vs cartridge filter debate has no universal winner. Each trades filtration fineness against effort, water use, and cost. Here is how they compare for a typical Ontario residential pool.
| Factor | Sand | Cartridge | DE |
|---|---|---|---|
| Filters down to | 20 to 40 microns | 10 to 15 microns | 3 to 5 microns |
| Cleaning effort | 2 min backwash | 30 min disassembly | Backwash plus recharge |
| Water wasted per clean | 200 to 400 L | None | 200 to 400 L |
| Unit cost installed | $900 to $1,600 | $1,100 to $2,000 | $1,400 to $2,400 |
| Media life | 5 to 7 years | 2 to 3 years | 7 to 10 years (grids) |
| Best for | Low effort owners | Water clarity, well water | Maximum clarity |
Our practical read for the GTA: sand is the right default for most families because the cleaning is trivial and nobody skips a two minute job. Cartridge is the better choice if you are fussy about water clarity, if you are on a well where refilling after backwash is slow, or if your municipality restricts backwash discharge. DE gives the finest water in the business but asks the most of you, and the powder needs careful handling.
The glass media upgrade
If you have a sand filter and want better clarity without changing tanks, recycled glass media is a straightforward swap. It filters closer to 10 microns, resists the calcification that eventually ruins sand, and typically lasts longer. Expect $350 to $550 installed. For Ontario pools on hard municipal water, this is often a better investment than a whole new filter.
How to Backwash Without Wrecking the Valve
A pool filter backwash reverses flow through the sand bed and flushes trapped debris out the waste line. It takes two minutes and there is exactly one way to ruin your equipment doing it.
The rule that saves the valve: always turn the pump OFF before moving the multiport handle. Rotating the valve while water is under pressure shears the internal spider gasket, and a failed spider gasket means water bypasses the filter entirely and leaks to waste continuously. It is the most common self-inflicted equipment failure we repair.
The sequence
- 1. Pump off. Always first.
- 2. Roll out the backwash hose to somewhere that can absorb a few hundred litres, away from garden beds and off your neighbour's property.
- 3. Set the valve to Backwash. Push the handle down and turn.
- 4. Pump on. Watch the sight glass. Run until the water runs clear, usually two to three minutes.
- 5. Pump off. Valve to Rinse.
- 6. Pump on for 30 to 60 seconds. This resettles the sand bed and clears the residual dirty water so you do not push it back into the pool.
- 7. Pump off. Valve to Filter. Pump on.
- 8. Top up the pool and record the new clean baseline pressure.
Skipping the rinse step is the second most common mistake. Without it, the first thirty seconds of filtering pushes a cloud of dirty water straight back into the pool, which is why some owners find their pool looks worse right after backwashing.
Cleaning a Cartridge Filter Properly
Cartridge filters cannot be backwashed. They come apart and get rinsed, which takes longer but wastes no pool water at all.
- Pump off, then release the air relief valve on top of the tank. Do not skip this. A pressurised filter lid can come off with real force.
- Open the tank and lift the cartridge out, noting its orientation.
- Hose it down from the top at a 45 degree angle, working around the element and spreading each pleat. Work top to bottom so debris washes down and out.
- Do not use a pressure washer. It drives debris deeper into the fabric and tears the pleats. A garden hose with a standard nozzle is correct.
- Inspect the pleats for tears, thin patches, and a collapsed core. Any of those means replacement.
- Check the tank O-ring and lubricate it with silicone grease, never petroleum jelly, which degrades rubber.
Worth the money: buy a second set of cartridges. Swap the clean set in, take the dirty set out to soak overnight at your leisure, and your pool is never down. For roughly $150 to $300 you turn a thirty minute chore into a five minute one, and cartridges that get properly soaked rather than hurriedly hosed last considerably longer.
The Annual Chemical Deep Clean
Rinsing and backwashing remove debris. Neither removes the two things that genuinely kill filter media: body oils and sunscreen, which glaze the surface, and calcium scale, which cements it. Both need a chemical soak, and both build steadily through an Ontario season.
For cartridges
Soak overnight in a proprietary filter cleaner, or in a solution of one part muriatic acid to twenty parts water for scale. Critically, degrease first and descale second. Acid applied over an oil glaze simply seals the oil in place and the cartridge comes out no better than it went in. Rinse thoroughly and let it dry completely before reinstalling.
For sand
Sand filters take a chemical cleaner poured into the skimmer or directly into the tank, left to sit overnight with the pump off, then backwashed out thoroughly in the morning. Do this once a season and you will meaningfully extend the life of the bed.
For DE grids
Remove the grid assembly, hose it down, then soak in filter cleaner. Inspect the fabric closely for tears, because a single torn grid sends DE powder straight back into the pool and creates a cloudiness that no chemical will fix.
In Ontario the natural time for this is at closing, so the filter goes into winter clean and comes out of winter ready. Doing it at opening also works, but you will be fighting for a service slot in a very busy month.
When Media Needs Replacing (and Costs)
Media does not last forever. Sand grains erode round and lose their ability to trap particles. Cartridge fabric stretches and glazes. DE grids tear. Here are 2026 Ontario figures.
| Media | Replace Every | Cost Installed (CAD) |
|---|---|---|
| Filter sand | 5 to 7 years | $250 to $450 |
| Glass media upgrade | 8 to 12 years | $350 to $550 |
| Cartridge element | 2 to 3 years | $80 to $300 each |
| DE grid set | 7 to 10 years | $250 to $500 |
| Multiport spider gasket | As needed | $150 to $300 |
Signs the media is done
- Pressure returns to high within days of a thorough clean
- Water stays hazy despite perfect chemistry and long run times
- Sand appears in the pool, which means a broken lateral rather than tired sand
- Backwash water never runs fully clear
- Visible clumping when you dig into the sand bed, a sign of calcification
The Ontario Season Schedule
Our season runs roughly five months, which means filter maintenance has a natural rhythm rather than a year-round grind.
May, at opening
Reassemble, inspect O-rings and the pressure gauge, backwash thoroughly after the first 48 hours of running, and record your clean baseline for the season.
June through August
Check pressure weekly. Clean at 8 to 10 PSI over baseline. Expect that to fall every two to four weeks in peak season, more often after storms or heavy use.
September
Leaf load climbs sharply. Empty skimmer baskets more often and expect more frequent filter cleaning even as swimming tails off.
October, at closing
Full chemical deep clean, then drain the tank completely and leave the multiport valve in the Winterize or between-positions setting. A filter tank left full of water will crack in an Ontario January.
That last point is the Ontario-specific one that costs people money. Filter tanks, like pumps, hold water that expands when it freezes. Draining the tank at closing is part of any proper pool closing service, and skipping it is a common cause of a cracked tank discovered in May.
The Bottom Line for Ontario Pool Owners
Good pool filter cleaning comes down to three habits: know your clean baseline pressure, clean at 8 to 10 PSI above it rather than on a calendar, and give the media one proper chemical soak per season. Do those and you will spend less on chemicals, less on hydro, and considerably less time wondering why the water looks dull.
On the sand filter vs cartridge filter question, pick sand if you value simplicity and cartridge if you value clarity. Both work well when maintained and both fail identically when neglected. If you would rather not track pressure gauges all summer, Swimpool 360 handles filter service, media replacement, and full seasonal maintenance across Toronto, the GTA, and York Region. Call 647-239-7665. We respond to all inquiries within 24 hours.
Frequently Asked Questions: Pool Filter Cleaning
How often should you clean a pool filter?
Clean when the pressure gauge reads 8 to 10 PSI above its clean baseline, not on a fixed calendar. In practice that means backwashing a sand or DE filter every two to four weeks during an Ontario summer, and deep cleaning a cartridge every four to six weeks. Every filter also needs one full chemical deep clean per season, best done at closing. Cleaning too often is counterproductive on sand filters, because a lightly loaded sand bed traps finer particles than a perfectly clean one.
Is a sand filter or a cartridge filter better?
Cartridge filters filter finer, roughly 10 to 15 microns versus 20 to 40 for sand, and waste no water because they are rinsed rather than backwashed. Sand filters are cheaper and cleaning takes two minutes instead of thirty. For most Ontario homeowners sand is the lower effort choice and cartridge is the better water quality choice. If you are on a well, or your municipality restricts backwash discharge, cartridge has a clear advantage. A glass media upgrade lets a sand filter approach cartridge fineness without changing tanks.
How do you backwash a pool filter?
Turn the pump off first, every time, because moving the multiport valve under pressure shears the internal spider gasket. Set the valve to Backwash, turn the pump on, and run until the sight glass runs clear, usually two to three minutes. Pump off, valve to Rinse, run 30 to 60 seconds to resettle the bed, then pump off and return the valve to Filter. Top the pool back up, since a backwash uses 200 to 400 litres, and record the new clean baseline pressure.
How much does pool filter media replacement cost in Ontario?
Replacing sand costs $250 to $450 in Ontario as of 2026 including labour, needed every five to seven years. Replacement cartridges run $80 to $300 each and last two to three years. DE grid sets cost $250 to $500 and last seven to ten years. A glass media upgrade for a sand filter runs $350 to $550 installed, filters finer than sand, and typically outlasts it. A failed multiport spider gasket, a common self-inflicted fault, costs $150 to $300 to put right.
Why is my pool filter pressure high after cleaning?
If pressure stays high right after a thorough cleaning, the media is exhausted or something downstream is restricted. On sand filters the usual cause is calcified or channelled sand that water flows around rather than through, which backwashing cannot fix. On cartridges it is oils and minerals embedded in the pleats, needing a chemical soak rather than a hose rinse. Also check for partly closed return valves and a heater bypass left shut, both of which raise pressure with no filter fault at all.
Related pool guides and services from Swimpool 360: