Pool Cartridge Filters 101: OEM vs Aftermarket & Service Scope

Pool Cartridge Filters 101: OEM vs Aftermarket & What We Actually Clean

We recently got a call from a customer — let’s call her Lisa — who had a great set of questions about her pool’s cartridge filter. She was trying to price out new cartridges, compare what she’d paid online versus what her husband paid in-store, and figure out what exactly should be cleaned when we service her filter.

By the end of the call, we’d walked through OEM vs aftermarket cartridges, why prices are all over the place, and what a proper filter service should include. If you’ve ever stared at a filter quote and thought, “Why is there such a big price difference?” or wondered whether your filter is really being cleaned thoroughly, this is for you.

OEM vs Aftermarket Cartridges: What’s the Difference?

Lisa had a Waterway Crystal Water 425 style setup (four cartridges), and she’d used both OEM (original equipment manufacturer) and aftermarket brands like Pleatco and others. Her main question: “Are the cheaper ones online really the same thing?”

OEM Cartridges

OEM cartridges are made (or contracted) by the same company that built your filter — Pentair, Waterway, Hayward, etc.

• Pros:
  • Exact fit and specs for your filter tank
  • Reliable micron rating and flow characteristics
  • Usually recommended for warranty compliance
• Cons:
  • Often more expensive than aftermarket
  • Pricing can vary a lot between local stores and online

Aftermarket Cartridges (Pleatco, Filbur, etc.)

Aftermarket cartridges are made by third-party manufacturers to fit OEM filter housings. Brand names you’ll see include Pleatco, Filbur, Unicel, and others, along with “house brands” some pool stores carry.

• Pros:
  • Often cheaper than OEM, especially online
  • Many reputable brands perform comparably to OEM
  • Wide availability and multiple options for the same model
• Cons:
  • Quality can vary a lot between brands
  • Some “bargain” cartridges use thinner fabric or less pleat area
  • Fit isn’t always perfect, which can affect sealing and flow

In Lisa’s case, she’d seen “genuine OEM” four-packs online for substantially less than what her husband had paid locally for another brand. That leads us straight into pricing.

Why Do Filter Cartridge Prices Vary So Much?

On the phone, we walked Lisa through why she might see a four-pack of 420–425 sq ft cartridges for around $260 online, while our in-stock set from a premium brand was $358. Here are the main factors:

1. Brand & Fabric Quality

Not all cartridges use the same quality of filter media (fabric). Better media holds more dirt, resists collapse, and cleans easier.

• Premium brands tend to cost more but often last longer and maintain good flow.
• Cheaper cartridges may have fewer pleats (less surface area) and wear out faster, even if they’re “the right size.”

2. OEM vs Aftermarket Markup

OEM parts can carry a higher MSRP. Aftermarket brands may undercut that pricing, especially online where overhead is lower. Local shops also factor in:

• Stocking and inventory costs
• Warranty handling and support
• Time spent matching the correct cartridges to your filter

3. Service vs “Just Parts”

Sometimes prices include more than just the plastic and fabric. For example, we often bundle:

• Cartridges
• Professional installation
• A full filter clean and system check while we’re there

Online, you’re paying for parts only. With a local company, part of the higher price is convenience, expertise, and a person you can call if something isn’t right.

What Should Be Cleaned During a Proper Cartridge Filter Service?

The most valuable part of Lisa’s call, in our opinion, was her question about what had actually been cleaned when the new cartridges were installed. She mentioned a knitted “sock” on the center pipe (a debris pre-filter) that hadn’t been touched and a dirty bottom in the filter tank.

Here’s what a thorough cartridge filter service should include.

1. Powering Down & Safe Disassembly

• Turn off the system and relieve pressure from the filter (very important for safety).
• Open the filter tank and carefully remove the cartridges.

2. Cleaning the Cartridges Themselves

• Rinse each cartridge between every pleat with a gentle, fan-style nozzle (not a pressure washer).
• Inspect for cracks, torn bands, or crushed ends.
• If the cartridges are heavily stained, oily, or very old, we’ll recommend replacement instead of just cleaning.

3. Cleaning the Filter Tank & Bottom “Sump”

This is the part many homeowners don’t see, but it matters. A good tech should:

• Rinse and vacuum or drain out dirt and debris from the bottom of the tank.
• Clear any buildup around the standpipe and internal fittings.
• Check the tank O-ring, lubricate it, and inspect the clamp or band for safety.

As Lisa pointed out, simply “sticking new cartridges in and leaving the dirt in the bottom” isn’t ideal, especially if the tank is clearly dirty.

4. Cleaning Additional Accessories (Like Socks & Screens)

Lisa had a knitted “sock” on the center pipe — basically a fine debris pre-filter. Accessories like that should be:

• Removed and rinsed clean during a filter clean or cartridge replacement
• Inspected for holes or tears (and replaced if they’re damaged)

Anything that catches debris before it hits your cartridges helps extend their life — but only if it’s actually being cleaned.

5. Reassembly & System Check

• Reinstall cartridges correctly, making sure they’re seated properly on the standpipe.
• Close and clamp the tank to manufacturer specs.
• Restart the system, purge the air from the filter, and check for leaks.

What We Do vs Weekly Pool Service

One important clarification that came up with Lisa: during regular weekly pool service, we do not open the filter tank every visit. That’s a separate, scheduled filter service. Most cartridge filters only need a full clean every 3–6 months, depending on use, environment, and water balance.

When we’re booked specifically to replace cartridges or perform a filter clean, that’s when all the steps above — including cleaning the tank bottom and any socks or screens — should be done.

How to Get the Most From Your Cartridges

If you’re trying to balance cost and performance like Lisa was, here’s what we usually recommend:

• Stick with reputable brands (OEM or well-known aftermarket).
• Match the exact model of your filter (label should show brand and square footage).
• Clean on a schedule — don’t wait until the pressure is sky-high.
• Ask your service company what’s included in a “filter clean” so expectations are clear.

If you’re unsure what cartridges you need or whether your filter is being maintained properly, we’re always happy to talk through it — just like we did with Lisa — and help you choose the option that makes the most sense for your pool and your budget.