leaking FNS Plus

satpoolguy

Active member
Sep 16, 2014
36
San Antonio, TX
I have an FNS Plus 48, installed in March 2013. Recently, it developed a leak where, or very near to, where the top and bottom meet. I am not sure how to best proceed and am hoping for insight. I've replaced the gasket (lubing it liberally), and it still leaks. I've inspected the band clamp and it looks fine, and I can't find any cracks in the top or bottom of the filter. The leak seems to move when I rotate the band clamp. I have tried installing the clamp "upside down" and the leak location still seems to match a point on the clamp. I have been tapping it into place as best I can with a rubber mallet (something I haven't done in 15+ years with no apparent issues) and I am torqueing the bolt until the spring is compressed. I did notice that the bottom swells slightly when I turn on the pump. I am not sure if it had been doing that previously. It is very slight, but noticeable if you look for it. The pressure reads normal and the grids are quite clean (just disassembled and cleaned everything late last week). Is it possible the clamp is the cause of the leak? Should I try replacing it? Or is the apparent correlation with the positioning of the clamp a red herring? If I should get a new clamp, how important is it to get a genuine Pentair vs an aftermarket?
 

PoolGate

Gold Supporter
TFP Guide
Jun 7, 2017
5,095
Damascus, MD
Pool Size
29000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Jandy Aquapure 1400
Is it out in full sun all day? They do degrade and do need to be replaced eventually. Amazon sells the vessel top and bottom but if you need one side I'd get both. Might be cheaper to just get a new filter.
 

PoolGate

Gold Supporter
TFP Guide
Jun 7, 2017
5,095
Damascus, MD
Pool Size
29000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Jandy Aquapure 1400
Could be the clamp, could be the vessel. Worth trying the clamp there isn't much to fail in the clamp though.
 

satpoolguy

Active member
Sep 16, 2014
36
San Antonio, TX
Could be the clamp, could be the vessel. Worth trying the clamp there isn't much to fail in the clamp though.
It looks like the clamp is $160...I'd hate to throw that money away if it is unlikely to solve the problem. I agree there isn't much to go wrong on the clamp.

Hopefully some other people will have thoughts.
 

bgray9

Bronze Supporter
Jun 26, 2015
76
Mesa, AZ
I've had trouble with my older FNS filter leaking around the joint and have replaced the gasket. My is an older unit, at least 9 years old and probably a bit more than that. My leak was minimal and stopped a few weeks after the last time I closed it up and I haven't opened up the unit now for awhile. I'm thinking I'll replace my filter unit in the near future, as I'm guessing it's the filter itself somehow having issues.
 

satpoolguy

Active member
Sep 16, 2014
36
San Antonio, TX
it sure sounds like the clamp is the culprit if the leak moves with the part on the clamp... :)
You would think that. However, I am not sure that was the case.

I ended up ordering an entire new filter. Between the cost of the clamp, my manifold being cracked and needing replacement soon, my filter grids probably needing replacement soon, and the uncertainty of what was causing the leak, it seemed to make more sense to get a whole new unit. When I received the unit, I installed the new band clamp (a somewhat updated design from my filter, btw) and the leak persisted, and also moved as I installed the clamp in different positions. So it seems that there is something amiss with my filter vessel. However, even after removing the original filter, enabling very close and detailed inspection, I am unable to find anything that looks like a problem.

Anyways, things are fine now with the new filter (running with the old manifold and grids to extract all usable life from them). And for anyone reading, replacing the filter is SO easy (assuming you are replacing with an identical model). I ended up experimenting with the bank clamp and then reusing some old components which added time, but if you're just doing a direct swap, it is literally < 10 mins work and requires no tools. The new filter comes completely assembled and ready to go, except for needing to screw on the gauge and valve.
 
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cowboycasey

Gold Supporter
LifeTime Supporter
TFP Guide
Jul 3, 2013
4,578
Fletcher, OK
That was a great test so something was broke in the vessel itself even though you can not see it... under pressure it was there... :)