Rust inside my new Pentair filter?


Silver Supporter
Jul 21, 2017
So I've just opened up my 3-month old pool filter for it's first cleaning and I noticed some rust stains on the inside of the filter:



Is this normal? Seems a little disappointing to me that Pentair would have any materials inside the filter that are prone to rust. :confused:


Mod Squad
LifeTime Supporter
TFP Expert
Jul 7, 2014
Bedford, TX

I have the same filter, which is about 4 years old now, and it has always had the same problem... :(

I find that I could go for a year between cleanings if my OCD would let me... I do it once in the spring and one in the fall, when the weather is warm enough to get wet.. :p

I have no idea if it is normal or not... but your pics look identical to my filter...

Thanks for posting,

Jim R.

Texas Splash

Mod Squad
LifeTime Supporter
TFP Expert
3-months old though? I wonder .... maybe worth contacting Pentair and showing them those pics just in case? They might try to point fingers at chemistry, but as long as your water isn't acidic and reacting to something metallic (which I doubt), I think they should have an explanation. I'd be curious to hear what they have to say.


TFP Expert
Mar 3, 2011
The affected area looks like the metal was damaged by the process used to close the ring.

Possibly the area was heated too much and the metal lost its corrosion resistance.

I suspect that a grinder and/or torch was used on the affected spots.

The discoloration of the metal looks like typical heat damage.


TFP Guide
Gold Supporter
Nov 13, 2017
Central California
Hmmm, I hope the inside of mine doesn't look like that. JamesW is on to something. I thought at first it might be the rivets or riveting process. But it's also streaking elsewhere. Second guess was the manufacturer's use of a lower grade metal (stainless, I'd like to think, but there are a lot of grades of stainless). Some attempt to shave a little more profit, no doubt. Maybe a change in supplier. Whatever it is, Pentain would be hard-pressed to claim it is anything but "a defect in material or workmanship."