Filter grid failure for a relatively new Pentair DE filter

pool_dufus

Well-known member
May 22, 2013
100
Dallas, TX
Today I had to have a service call after tearing down my system for a routine cleaning and being unable to figure out why I was blowing DE back into the pool when I recoated the grids. After some close inspection with the pool guy we finally saw that ALL but one of my grids and totally blown out at the bottom of the grid. There were no threads left and the bottom of the grid material on all but one of my grids was totally open ... not just a small rip ... but the entire bottom of the grid material was totally open and there was not stitching left at all or evidence of stitching. Pool guy said he had never seen this before.

No, I back-flush pretty regularly and no, I did not have any pressures on the gauge above 20 psi. I maintain my chemistry and its never been out of hand.

I am thinking I got a batch of bad grids all manufactured at the same time. Only the short grid was OK. All of the long ones were blown out. The system was 4 years old. It was an expensive day.

Anybody else experienced grid failure from Pentair grids purchased in the 2014 time frame??
 

JamesW

TFP Expert
Mar 2, 2011
16,589
Sounds like the water is going backwards. Maybe plumbed backwards or wrong multiport.

Was the dirt and de inside the grids or outside?

Water blowing into the fabric will blow them up like a balloon and rip the stitching.

Water going the correct way will push the fabric onto the skeleton and keep the fabric closed.
 

pool_dufus

Well-known member
May 22, 2013
100
Dallas, TX
Sounds like the water is going backwards. Maybe plumbed backwards or wrong multiport.

Was the dirt and de inside the grids or outside?

Water blowing into the fabric will blow them up like a balloon and rip the stitching.

Water going the correct way will push the fabric onto the skeleton and keep the fabric closed.
Outside. They worked fine for 4 years, no problem.

Don't know why suddenly the water direction would change with no changes to the system, which has worked properly since we bought the house 7 years ago.

Apparently, the water did keep the rips closed. It wasn't until I broke the system down, cleaned the grids, and replaced them, that the problem occurred. Apparently, some of the tears did not get sealed when I put the grids back in.
 

JamesW

TFP Expert
Mar 2, 2011
16,589
Are these original Pentair grids?

It's unlikely that name brand grids would do this.

What model filter?

Do you have a picture of the system?
 

pool_dufus

Well-known member
May 22, 2013
100
Dallas, TX
Pentair FNS Plus Model FNSP 60 (60 sq. ft). Manufactured in 2013 and installed in 2014. The grids were the original ones for the filter, not aftermarket.

Unfortunately, I had the pool service haul them away before I made pictures. It was amazing. The whole bottom seam of every one of the large grids was totally open as if they had never been sewn. In most cases, the stitching thread was missing completely. You could have pulled the plastic inside structure out of the opening with no problem. Interestingly, the small grid was just fine, suggesting to me that there was some kind of manufacturing flaw for the large grids that came with my unit.

The filter was torn down a few times before, cleaned, and reassembled with no problem. Very puzzling.
 

jfmorris

Active member
Jun 4, 2013
40
Huntsville, AL
I think pool chemicals are hard on the fabric and stitching of the grids, and the plastics. Maybe these were not sewn in the bottom, but glued or something instead, and the glue disentegrated. That said, I didn’t replace the grids on my Hayward DE filter until they were over 10 years old, so agree that this seems like premature failure.
 

JamesW

TFP Expert
Mar 2, 2011
16,589
I still think that the water might be going backwards. Was the fabric loose and puffy or pushed against the internal plastic?
 

pool_dufus

Well-known member
May 22, 2013
100
Dallas, TX
@JamesW-
Pushed against the internal plastic. That's why I missed the tears when I took them out to hose them down. The pool service guy was about to put them back in and happened to notice the bottom of one was open when you looked closely. Closer inspection showed all of the larger grids were bad, all open at the bottom, but yes, hot flared out but pushed in.

How can the water flow backwards??
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
14,586
Bedford, TX
What JamesW is not saying is that we have seen this before and that the pool owners never knew that had a problem until the grids or cartridges gave up the ghost!!!

Jim R.
 

pool_dufus

Well-known member
May 22, 2013
100
Dallas, TX
Everything is possible, of course, but I have lived in this house for 7 years with no problems. The pool has been in for decades with no evidence that the plumbing has been modified. In 2013 I tore the system down to clean the grids and that’s when I discovered somebody had put a mixed size set of grids in the old unit. That’s when I replaced the entire filter with the new Pentair. Has worked just fine with no leaks and was torn down last year with these same grids, no problems.

It’s a (expensive) mystery. Pool is clear as a crystal now.
 

JamesW

TFP Expert
Mar 2, 2011
16,589
Yes, it should have a model number.

If they used a sand filter multiport or plumbed it wrong, the water will go backwards.

Is your backwash valve a multiport or a push/pull slide valve?
 

JamesW

TFP Expert
Mar 2, 2011
16,589
The only other possibility that I can think of is leaving the valve on backwash for a long time to lower the water level or trying to vacuum to waste, especially if the pump is high horsepower.