Do fiberglass filters wear out?


Sep 15, 2008
I have a filter that is of unknown age. It is a 24" Pentair Triton (though I'm not sure it is Pentair as the label is not fully there; the only legible part says Triton) on a 28000 gallon fiberglass pool.

I had noticed that the top of the filter would flex up to 1/4" or more when the pump would kick on (with or without cleaning and having air in it), once it got pressurized. I backwashed today and the o-ring began leaking. The o-ring needs replacing, so in the meantime I jellied it up to get it to seal. That did not stop the leak, and once fully pressurized, the filter cap will either pop up a full thread or pop off. I inspected the threads and it looks like in one section about 2 inches wide, they are worn; likely due to the flexing cycles of the filter upon pressurization. I also have a manual bleed and with it open, even partially or fully bled it will still pop off. The system typically operates between 18-24 PSI.

So that leads to the questions at hand:
Am I correct in assuming this filter is at the end of its usable life and needs replacing?
Are the threads causing the cap to pop loose, or do I have a different problem?
What should I replace with? I was thinking of going with a 30" Triton II. It should go right in place on my current collar setup, right?
Where is the best deal on a direct fit replacement sand filter?



In The Industry
Dec 22, 2008
Worn threads would signal a need for replacing the filter.

The larger filter would increase the filter area which would decrease your pressure. That would reduce stress on the filter, increasing it's life. Keep in mind that your current filter is meant for 63gpm max, and the 30" is 98gpm max. Size your pump accordingly, or go with an intelliflo.


Mod Squad
TFP Expert
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In The Industry
Apr 1, 2007
Sebring, Florida
I'm with cadillac.....I think it's close to time for a new filter. I have a large Triton II and I am a big fan (mine flexes, too).

30" sounds just about perfect for your pool but, more importantly, match it to your pump as cadillac indicated. A 1HP pump would be plenty for that size pool and would match the filter as well.


TFP Expert
May 21, 2010
Cary, NC
Fiberglass filters DO flex normally under operation. The damage you've seen on the threads probably indicates its time to replace though. All filters wear out eventually. Pentair's fiberglass filters are tested to over 10 times the industry life cycle standards, so you shouldn't have to replace them very often.

I will tell you that our new competition in fiberglass doesn't test anywhere near as well as the Triton, so my comments apply only to Pentair's fiberglass filters.