Recommended thread for repairing filter grids

[TXaquaholics]

Hey guys. I have a set of Pentair FNS Plus DE filter grids in which the bottom seam has failed on every single one after the first full cycle (complete tear down and cleaning). We previously used our sewing machine and thread on hand but that didn't last. Looking for what others have used for thread in this application. I have also seen references to hot glue being used but prefer the thread approach.

Before you blame backwashing, please know that isn't the cause. I never backwash and get 6 months of use before 10 psi delta rise and complete tear down/cleaning. That's due to use by two adults only and the fact I run with hair nets in the skimmer baskets (this catches a lot, including pollen!). Research here in the forums would indicate I ended up with a bad patch of Pentair grids as they are in the same date range that others have experienced this same issue.

Thanks!

 

[newdude]

I don't know of a material to use but I'd suggest ensuring it's plumbed correctly. It sounds like cartridges blowing/ripping after switching from sand/de because the ports are backwards.

Or it could be part of the modern 'shortage supply' where quality control has gone to crud everywhere.

Backwashing for a reasonable amount of time shouldn't ever cause damage.

 

[proavia]

I never backwash and get 6 months of use before 10 psi delta rise and complete tear down/cleaning.

We recommend cleaning the filter when the pressure increases 20%-25% above clean pressure - measured with RPM at around 3000RPM or higher.
Waiting until the pressure rises 10psi is too long between cleanings.

 

[TXaquaholics]

I don't know of a material to use but I'd suggest ensuring it's plumbed correctly. It sounds like cartridges blowing/ripping after switching from sand/de because the ports are backwards.

Or it could be part of the modern 'shortage supply' where quality control has gone to crud everywhere.

Backwashing for a reasonable amount of time shouldn't ever cause damage.

I can assure you it's plumbed correctly. Same config since 2008. The Pentair DE filter was changed from FNS PLS 48 to FNS PLS 60 a couple years back when the original 2004 filter cracked and sprung a leak. That's when the new grids went in service. If you search the forums here you will see others had the same issue. Sounded like a bad lot of filter grids.

Others responses here suggested backwashing could blow out the seams. I just wanted to convey that wasn't the root cause for my seam issue.

 

[TXaquaholics]

We recommend cleaning the filter when the pressure increases 20%-25% above clean pressure - measured with RPM at around 3000RPM or higher.
Waiting until the pressure rises 10psi is too long between cleanings.

Good feedback. Thanks. I was still using the old manufacturer guidelines of 10 psi increase. Especially now that I have a VSF pump I need to adjust for more frequent cleanings.

That being said, I still don't have any recommendations on closing up these relatively new otherwise perfectly usable grids. On the positive side, I have two grid packs so I can swap them out and go back into service quickly and take my time to clean properly.

 

[TXaquaholics]

Planning to try nylon upholstery thread this time around.