Filter pressure after transition to cellulose fiber

AceHigh · Apr 19, 2024

Hi all, new here and starting to dig into all the great knowledge here... Really glad this site exists!

I have a question - I learned how to do a full clean of my Pentair fns plus 48 de filter on YouTube

and decided to do the recharge with cellulose fiber this time around. (Wanted to do perlite but couldn't find any in my area)

But after the full clean and recharge... the pressure on my filter is only like 1 or 2 PSI. Shouldn't it be higher? Before the clean it was running around 20 PSI (I believe it was filled with DE, not sure though. Just bought the home.)

I bled air from the release valve when I restarted so I don't think air is the problem... And there aren't any obvious leaks or anything.

Any thoughts here? Or am I just incorrect in thinking that the pressure should be higher?

Thanks all! Looking forward to taking charge of my own pool maintenance rather than paying others!!

1poolman1 · Apr 19, 2024

AceHigh said:
Hi all, new here and starting to dig into all the great knowledge here... Really glad this site exists!

I have a question - I learned how to do a full clean of my Pentair fns plus 48 de filter on YouTube and decided to do the recharge with cellulose fiber this time around. (Wanted to do perlite but couldn't find any in my area)

But after the full clean and recharge... the pressure on my filter is only like 1 or 2 PSI. Shouldn't it be higher? Before the clean it was running around 20 PSI (I believe it was filled with DE, not sure though. Just bought the home.)

I bled air from the release valve when I restarted so I don't think air is the problem... And there aren't any obvious leaks or anything.

Any thoughts here? Or am I just incorrect in thinking that the pressure should be higher?

Thanks all! Looking forward to taking charge of my own pool maintenance rather than paying others!!

Its not unusual at all for the pressure to be much less with cellulose fiber, as long as the correct amount was added. First started using it in 1992-1993 when it first became available for pools. Was told by the manufacturer's rep to expect very different pressure-gauge readings. Would watch the pressure go down as the fiber was added to the skimmer and fill the filter. The proper amount for your filter is one full scoop in an orange DE scoop as in the picture. Works everytime.

Be aware that if you didn't do a soak of the grids to remove any oils on them (there's always oils in a filter) you will have to do a backwash/clean out of the fiber rather quickly. The rep warned me of that and its very true, so don't be disappointed if it happens to you, its normal for the product. The cellulose will soak up any oils in the grids and turn into a gooey mess the first time if oils weren't removed or new grids installed.

That's why so many in my area immediately hated the product, which was fine with me as they gave me what wasn't used. Servicing many commercial pools at the time, it saved me quite a bit of money on a product I wouldn't do without. I went from using 400# of D.E. per month to 1- 25# bag (which is the equivalent of 200# D.E.) per month and had water that sparkled

AceHigh · Apr 19, 2024

1poolman1 said:
Its not unusual at all for the pressure to be much less with cellulose fiber, as long as the correct amount was added. First started using it in 1992-1993 when it first became available for pools. Was told by the manufacturer's rep to expect very different pressure-gauge readings. Would watch the pressure go down as the fiber was added to the skimmer and fill the filter. The proper amount for your filter is one full scoop in an orange DE scoop as in the picture. Works everytime.

Be aware that if you didn't do a soak of the grids to remove any oils on them (there's always oils in a filter) you will have to do a backwash/clean out of the fiber rather quickly. The rep warned me of that and its very true, so don't be disappointed if it happens to you, its normal for the product. The cellulose will soak up any oils in the grids and turn into a gooey mess the first time if oils weren't removed or new grids installed.

That's why so many in my area immediately hated the product, which was fine with me as they gave me what wasn't used. Servicing many commercial pools at the time, it saved me quite a bit of money on a product I wouldn't do without. I went from using 400# of D.E. per month to 1- 25# bag (which is the equivalent of 200# D.E.) per month and had water that sparkled
View attachment 565695

Thanks for the response!

I didn't do anything special to remove oils, so I will take note that I'm going to have to service the filter sooner. My plan was to do a full clean and replacement of the cellulose every 6mo.s does that sound right or should I expect to do one in like 3 mo.s this first time around?

1poolman1 · Apr 19, 2024

AceHigh said:
Thanks for the response!

I didn't do anything special to remove oils, so I will take note that I'm going to have to service the filter sooner. My plan was to do a full clean and replacement of the cellulose every 6mo.s does that sound right or should I expect to do one in like 3 mo.s this first time around?

You may have to do it much sooner than that if there are a lot of oils in the grids. You will find that a backwash of the cellulose will remove almost all from the filter, but "your mileage may vary." The first backwash won't remove much if there are oils involved. After that you may not need to do a teardown for a year, or whatever makes you comfortable, its your pool. I like to look at the grids every year to be sure there are no tears, holes, broken grids, etc.

AceHigh · May 7, 2024

1poolman1 said:
You may have to do it much sooner than that if there are a lot of oils in the grids. You will find that a backwash of the cellulose will remove almost all from the filter, but "your mileage may vary." The first backwash won't remove much if there are oils involved. After that you may not need to do a teardown for a year, or whatever makes you comfortable, its your pool. I like to look at the grids every year to be sure there are no tears, holes, broken grids, etc.

Thanks for the heads up on this. It hasn't even been a month and it looks like it's time already

Hopefully all the oils are out and it won't be this short of a time between cleaning going forward.

Do you know if it's possible to replace the filter / filter assembly with one that's easier to clean like the traditional cylinder filters I see on YouTube?

Or is this spiral "grid" system the only thing that works with a Pentair FNS Plus 48?

1poolman1 · May 7, 2024

AceHigh said:
Thanks for the heads up on this. It hasn't even been a month and it looks like it's time already

Hopefully all the oils are out and it won't be this short of a time between cleaning going forward.

Do you know if it's possible to replace the filter / filter assembly with one that's easier to clean like the traditional cylinder filters I see on YouTube?

Or is this spiral "grid" system the only thing that works with a Pentair FNS Plus 48?

Are you wanting to convert to non-D.E. cartridge filters? Can it be done with your tank? Yes. Would you want to spend the time and cost (up to near $1000.00 with new cartridges) to make that conversion? Then a replumb of the system as the inlet and outlet of the tank are reversed and the backwash valve will go away. Probably not.

AceHigh · May 7, 2024

1poolman1 said:
Are you wanting to convert to non-D.E. cartridge filters? Can it be done with your tank? Yes. Would you want to spend the time and cost (up to near $1000.00 with new cartridges) to make that conversion? Then a replumb of the system as the inlet and outlet of the tank are reversed and the backwash valve will go away. Probably not.

No no, didn't mean moving to a non-DE filter, just meant is there another DE filter I can use that isn't as complicated as this spiral filter that I currently have. I'm attaching a picture of the current filter (before it was cleaned!)

These grids are quite difficult to clean and put back together. The DE filters I've seen online take cylindrical cartridges and seem much easier to clean.

DavidArmenB · May 8, 2024

AceHigh said:
No no, didn't mean moving to a non-DE filter, just meant is there another DE filter I can use that isn't as complicated as this spiral filter that I currently have. I'm attaching a picture of the current filter (before it was cleaned!)

These grids are quite difficult to clean and put back together. The DE filters I've seen online take cylindrical cartridges and seem much easier to clean.

You are referring to Quad DE filters:

I am not sure if you can convert an FNS plus to a Quad DE unless you are prepared to change all the internal components and plumbing, if that is a possibility at all.

1poolman1 · May 8, 2024

AceHigh said:
No no, didn't mean moving to a non-DE filter, just meant is there another DE filter I can use that isn't as complicated as this spiral filter that I currently have. I'm attaching a picture of the current filter (before it was cleaned!)

These grids are quite difficult to clean and put back together. The DE filters I've seen online take cylindrical cartridges and seem much easier to clean.

Again, it can be done as the tanks are the same. But, the cost to do so and the work involved are very high. You would need the 4, properly sized DE cartridges (don't know which size would fit your tank, likely Quad 60, +/- $170.00), new everything in the tank (including the air relief tune at about $40.00), along with replacing the bulkhead fittings for best results. The system would need to be re-plumbed to accommodate a new valve or just to plumb direct. You might save your existing valve, but a complete re-plumb of it would be needed to account for the different flow in and out of the filter.
Or buy a new filter.

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Filter pressure after transition to cellulose fiber

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