DE Leaking into pool - what to do next?

[poolnovice1]

I have a 4 year old Pentair FNS Plus 60. I maintain my pool but have a pool guy clean the filter every year. After a cleaning 2 years ago, the filter has been leaking DE every time I backwash or get the filter cleaned. The DE comes out of the return jets.

The pool guy says he's checked the grids and doesn't see a tear.

Should I just bite the bullet and replace the grids even if there are no visible tears? Is there anything else it could be? I'm thinking that since the leak started after the cleaning done in 2020, the guy must have torn a grid while cleaning.

 

[AQUA~HOLICS]

One possibility if it started right after the filter was disassembled is that it has a crack in the manifold or a o-ring that needs replacement. Take the filter apart your self and inspect it. If it’s a grid this will most often occur on the corners/seams.

 

[poolnovice1]

One possibility if it started right after the filter was disassembled is that it has a crack in the manifold or a o-ring that needs replacement. Take the filter apart your self and inspect it. If it’s a grid this will most often occur on the corners/seams.

I usually pick up 1-2 lbs DE in my cleaning robot over the course of a week or two. I suspect 90% of the DE leak happens immediately after turning the pump back on. I'm wondering if I'm just adding too much DE. I usually add 4.5 lbs back in after backwashing. If there was a leak, wouldn't most of the DE end back up in the pool?

 

[AQUA~HOLICS]

Just the fact that DE is getting past the filter grids and into the pool may not be due to the amount of DE but it taking the path of least resistance in an opening.

 

[ferretbone]

Check the top and bottom of the manifold for cracks, then use a screw driver to push into the 2inch manifold hole into the top of it. Try to separate the top of the manifold from the bottom. The top of the manifold can split and you would never see that unless you do that little test. Next up check to be sure the grids are fully seated into the manifolds ports. All eight. If one looks shorter going into a port than the rest thats a DE leak.

 

[HermanTX]

The pool guy says he's checked the grids and doesn't see a tear.

Should I just bite the bullet and replace the grids even if there are no visible tears? Is there anything else it could be?

While grids are usually the main reason for leaking DE, i would think it would get worse over time if it was a tear. Look at each grid carefully, close to the seams. You can fill them from the top with water hose as well and try to see a tear As the water flows down the grid.
However, there are other leak paths
The air relief screen on top of plastic manifold - there is usually a small screen depending on the model
The oring on the standpipe where the manifold sits on top-if that is cut or missing
Each of the grids seat in the bottom of the manifold - if they are not seated properly during reassembly, they they could allow a path for DE
The manifold itself - it is plastic and if banged around during disassembly or just old age, then it can crack and may only leak when pressurized.

So your pool service tech should look at other things - not just the grids. This should not be going on for 2 years if the pool service tech was trying to identify the issue. Sorry this has not been addressed by the service tech sooner.

 

[rockaway99]

I'm also experiencing DE leak. Replaced all the grids, and the standpipe oring. Replaced the air relief screen. Re-opened the tank after DE was still leaking in - carefully inspected the manifold and grids and carefully re-assembled the manifold atop the grids - all seemed well. Still leaking! I give up!
Next, replace filter. FNSPlus48 8 years old.

 

[HermanTX]

carefully inspected the manifold

A crack in the manifold may only be seen when the system is pressured up. This may be why you cannot see it when disassembled. Since you purchased new grids, it may be worth purchasing a new manifold before purchasing a new filter. In fact, you will have a new filter with new grids and new manifold. So long as the housings are in good condition.

 

[rockaway99]

A crack in the manifold may only be seen when the system is pressured up. This may be why you cannot see it when disassembled. Since you purchased new grids, it may be worth purchasing a new manifold before purchasing a new filter. In fact, you will have a new filter with new grids and new manifold. So long as the housings are in good condition.

Thank you Herman - appreciated. The manifold has to be the last possible problem. I'll try it.

 

[rockaway99]

Well, the new manifold is in and relief was noticed - for awhile.
Seems that the problem only occurs when the pool calls for solar.
At that point the pump bumps up to accommodate the water going to the roof. I get a brief surge of DE into the pool followed by a regular particulate stream - as far as I can tell only during the solar cycle. There are no discernable leaks visible and the level hasn't changed much. I get some air build-up in the filter, noticeable when I turn the air relief valve. I'm throwing my hands up at this now.
So it's time to retire the DE filter, imo. There are enough good cartridge alternatives on the market.
On that note, I'm looking at (among others) a Pentair Clean & Clear 420. Reason is it has the same footprint as the FNS+ so maybe I can get by with simply undoing the unions and replacing the filter. Otherwise, there's mucho plumbing to be done.
So the question is: can I leave the Multiport valve in place with the 420? I know I don't need the functionally of a multiport, but can I just leave it on Filter mode? That would make a huge difference in the plumbing. If I need to re-plumb, I'll go with a pre-filter/cartridge combo from Circupool and try to find a good plumber.

 

[HermanTX]

Sorry to hear the new manifold did not solve the issue.
The CCP420 is a great filter. As you indicated, the MP valve is not needed but it does give you access to the waste line which is nice.
if you do opt to remove the MP valve then I would still plumb in the waste line using a 3-way valve.before the filter.

 

[poolnovice1]

Replacing the grids and manifold solved the DE leak for me.

 

[HermanTX]

Replacing the grids and manifold solved the DE leak for me.

great to know that it got resolved. Leaks in a manifold and /or a grid can be hard to find.