The Best Bullfrog Spa Filter Replacements

The verdict, up front. Bullfrog uses two completely different filter formats, and which one you need is decided by your tub’s series and its year. The newer A, M and Swim series take a flat rectangular filter panel. Older tubs, including Wellspring 30 housings, take a round coreless cartridge in the PBF40M pattern.

These are not alternatives to each other. A flat panel will not go in a cartridge housing and a cartridge will not go in a panel slot, so the first thing to do is open the filter compartment and look. Everything else on this page follows from that.

How we judged these

Flat filters or round cartridges: how to tell

Open the filter compartment and look at what is in there. A flat filter is a thin rectangular panel, roughly 10.4 by 8.2 inches and about an inch and a quarter thick, that slots in. A coreless cartridge is a round pleated tube about 8 inches across and 6 1/4 inches long with an open hole at each end.

As a rule of thumb, A and M series tubs built from 2023 onward, plus the Swim series S150, S180XD and S200, use the flat panel. Earlier tubs and Wellspring 30 housings use the cartridge. The rule of thumb is not a substitute for looking, because ranges overlap at the changeover and some tubs were built either side of it.

The end-hole trap on coreless cartridges

This is the most useful thing on the page, and it is not obvious. Two listings can both claim the Pleatco PBF40M pattern and quote different end-hole sizes: one gives 3 3/8 inches at both ends, another gives 3 3/8 at the top and 4 1/2 at the bottom. Those are not the same part in a housing, whatever the cross-reference says.

So measure the holes on the cartridge you are taking out, write both numbers down, and buy the listing that states your numbers. A cartridge with an undersized hole will not seat on the standpipe; one with an oversized hole lets water run straight past the pleats, which looks like a working filter and filters nothing.

Coreless also means exactly what it says: there is no rigid plastic center tube, so the cartridge relies on the housing to hold its shape. If your old filter had a hard core inside it, you do not want a coreless one.

The pre-2017 second filter

Tubs built before 2017 may need an additional filter cartridge alongside the main one, which the better listings say outright. Count the elements in the housing before assuming a two-pack is a complete set. This is the same trap Master Spa owners hit with two-part Eco-Pur systems, and it produces the same symptom: a tub that never quite clears after what seemed like a full filter change.

Flat filters are a faster consumable

Listings for the flat panels recommend replacement every one to two months, which is dramatically more often than a pleated cartridge. That is not a defect, it is the design: the panels are thin, cheap, and sold in fours because you go through them.

Budget accordingly. Four panels a year is a different purchase from four panels a quarter, and if you are running the tub hard the cadence is closer to the latter. The upside is that a fresh filter is genuinely fresh rather than a three-year-old cartridge you have soaked eleven times.

Flat filters also rinse rather than soak well. A cartridge rewards a proper chemical soak — see filter cleaners — whereas a thin panel is usually easier to hose off and eventually swap.

OEM part numbers worth knowing

• 10-00814. The flat filter panel for the newer A, M and Swim series.
• 10-00282. The round coreless cartridge, also sold as Pleatco PBF40 and PBF40M, rated at 30 square feet of filtration area.

Both numbers appear across multiple sellers, which is good news for a consumable: you are not locked to one supplier. Where two listings for the same number differ on dimensions, trust your own tape over either of them.

A clean filter is not a sanitizer

Worth repeating on every filter page. Filtration removes particles; it does not disinfect. Public health guidance for hot tubs is built around holding a measurable residual at a controlled pH — pH 7.2 to 7.8 with at least 3 ppm free chlorine or 4 to 8 ppm bromine — regardless of what is in the filter housing.^[source]

What a fresh filter buys you is sanitizer that is not being spent on suspended dirt. On a tub running month-old flat panels, that difference is noticeable.

On prices, and on what these scores are

Bullfrog filters are inexpensive individually and add up over a year, which is why the four-packs and two-packs are the sensible unit of purchase. Every button reads the live price where our price layer has one; anything we cannot verify, we do not print — the reasoning is on how we pick.

The scores are an editorial judgment of published fit information, stated media, pack economics and how many sellers carry the pattern, against our published method. We have not tested these filters, we make no performance claims on their behalf, and there is no rating markup in this page’s structured data.

The honest summary

Look in the filter compartment first. A flat panel means the 10-00814 pattern and a four-pack is the right purchase, because you will be changing them every month or two. A round cartridge means the 10-00282 or PBF40M pattern — measure both end holes before you order, because listings disagree, and count the elements if your tub predates 2017.

If you want the general method rather than the Bullfrog-specific one, the filter finder walks through matching any cartridge to any tub, and when to replace a hot tub filter covers judging condition rather than counting weeks.