Pool filtration is one of those subjects where the operator who knows it cold can upsell a $1,200 filter swap on a service call, and the operator who does not loses the customer to whoever explains it clearly. There are three filter technologies in residential pool service: DE (diatomaceous earth), sand, and cartridge. Each has a different micron rating, a different cleaning rhythm, a different cost profile, and a different ideal customer. This is the operator reference for which filter goes where, what to charge, and how to recommend the right one.
TL;DR
- DE filters: 2 to 5 micron filtration, the cleanest water, monthly backwash, replace DE powder annually
- Sand filters: 20 to 40 micron filtration, easiest to maintain, backwash as needed, replace sand every 5 to 7 years
- Cartridge filters: 10 to 20 micron filtration, no backwashing, hose cleaning every 1 to 3 months, replace cartridges every 2 to 5 years
- Cartridge is the most common new install in 2026 because of water restrictions on backwashing
- DE produces the highest water clarity but requires the most operator skill
- Sand is cheapest to maintain but worst at fine debris and dead algae
The 3 filter technologies in residential pool service
Residential pool filtration in 2026 falls into three categories: DE (diatomaceous earth), sand, and cartridge. Each works on a different physical principle. DE traps particles in a powder-coated grid. Sand traps particles in a graded media bed. Cartridge traps particles in a pleated polyester element. The differences in micron, maintenance, and cost are what drive operator and customer choice.
A typical pool service route has all three types because installations vary by builder, region, and era. Knowing how to service each one and which one to recommend on equipment upgrades is the difference between handling a callback and selling a system.
DE filters: the cleanest water option
DE filters use diatomaceous earth powder coated onto a set of internal grids. Filtration is 2 to 5 micron, which is the finest of the three technologies and produces the clearest water. Pools with DE filtration look noticeably different than pools with sand or cartridge: water is glassy clear at every depth.
Maintenance: backwash monthly (or when pressure rises 8 to 10 psi above clean baseline), then recharge with fresh DE powder through the skimmer. Full grid breakdown and rebuild annually. DE powder cost is roughly $30 to $60 per recharge. Grid replacement runs $300 to $600 for the set, every 5 to 8 years.
Drawback: DE handling has a regulatory layer in some jurisdictions (California, parts of Arizona) because spent DE is technically a hazardous waste. Service operators should not backwash to landscape or storm drain. Most municipalities require backwash to sewer cleanout or a containment pit.
Sand filters: the easiest to maintain
Sand filters are the workhorse of the pool industry. Filtration is 20 to 40 micron (or 5 to 10 micron with the addition of zeolite or filter aid). Maintenance: backwash when pressure rises 8 to 10 psi above clean baseline, usually every 2 to 6 weeks. Replace the sand bed every 5 to 7 years (cost $80 to $150 in sand plus 1 to 2 hours labor).
Sand handles heavy debris loads well, recovers quickly from algae blooms, and tolerates inexperienced techs. The downside is filtration is not as fine as DE or cartridge, so the water is clean but not glassy. Sand pools sometimes show a slight haziness in direct sunlight, especially after high bather load.
Cartridge filters: the no-backwash option
Cartridge filters use a pleated polyester element (the cartridge) inside a tank. Filtration is 10 to 20 micron, somewhere between sand and DE. No backwashing required; cleaning is hose rinsing the cartridge every 1 to 3 months. Cartridge replacement every 2 to 5 years depending on usage, at $80 to $250 per cartridge.
Cartridge has become the most common new install in 2026 because many municipalities (especially in California, Arizona, Nevada) now restrict or ban backwashing to landscape. No backwash means no water waste and no sewer connection requirements. For service operators, cartridge is also the lowest stress technology: nothing to time, no recharge step, just pull and hose.
Which filter for which customer
A service operator recommending a filter for a customer should match the filter to the customer's priorities, not to a default.
- Customer values water clarity above all (entertainment pool, weddings, premium home): DE
- Customer wants the easiest maintenance (vacation home, low priority): cartridge
- Customer has high debris (lots of trees, heavy bather load, large pool): sand
- Customer is in a water-restricted municipality with no sewer cleanout: cartridge
- Customer has a saltwater system: cartridge or DE (sand handles salt fine but cells last longer with finer filtration)
Filter sizing matters more than type
Most filter underperformance is undersizing, not the filter type itself. Filter capacity (gallons per minute, plus square feet of filter area) should match or exceed the pump's turnover capacity. A 1 HP pump moves roughly 60 GPM. A sand filter rated for 50 GPM will be overdriven and the water column will channel, dropping filtration efficiency.
Standard residential sizing: at least 400 to 500 sq ft of cartridge surface, 24 to 30 sq ft of DE grid, or 19 to 25 sq inch port sand. When in doubt, oversize. Bigger filter means longer time between cleanings and better filtration at the same pump speed.
“An undersized filter is a clean filter that does nothing. Oversize when the budget allows.”
Pressure as the universal indicator
Every filter type uses pressure as the cleaning indicator. Clean filter baseline pressure is typically 10 to 15 psi above the gauge's zero. When pressure rises 8 to 10 psi above baseline, it is time to clean. This is true for all three filter types.
Operators who clean on a calendar instead of on pressure either over-clean (sand bed channels, cartridge wears, DE grids damaged) or under-clean (filter restricts flow, pump runs hot, energy waste). Pressure tells you exactly when to clean.
The replacement and repair business
Filter replacements are a significant revenue line for pool service operators. A full DE filter swap (new tank, grids, DE) runs $1,000 to $2,500 parts and labor. Sand filter replacement runs $800 to $1,800. Cartridge filter replacement runs $800 to $1,500.
Service operators who track filter age in their software (year of install, brand, model) can preemptively offer upgrades before failures. A 15 year old sand filter on a customer who has been with you 5 years is a $1,200 upsell waiting for the right conversation.
Common filter mistakes that cause callbacks
- Backwashing a sand filter every visit. Damages the sand bed and channels develop
- Adding DE through the skimmer with the filter valve in backwash position. DE blows out the waste line
- Hosing a cartridge with high-pressure water. Damages the pleats
- Not coating DE grids after backwash. Filter runs without DE for 30+ minutes; particles bypass the grids
- Ignoring the pressure gauge. Filter runs restricted for weeks before the operator notices
- Re-installing an old cartridge with visible tears. Filter does no work, water stays cloudy
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