Filter Size Question

[Mr. Blue]

New pool owner here.

I have a Pentair FNS Plus filter, but do not know the filter size. On the side of the filter, there is a chart where the person installing the filter was supposed to 'check off' the model number (see below). As you can see, no one did this.

The person that was "maintaining" the pool said she was told to add 6 cups of DE after backwashing. Yet, when I look at the filter, the minimum size listed is 36ft, which would call for 8 cups (based on the chart on the bag of DE).

Is there a way to tell what the filter size is for sure?

 

[Isaac-1]

DE really should be weighed, using scoops can be WAY OFF depending on how packed the DE is.

 

[Richard320]

I had the same problem when I started.

What I did was measure the height of the grids when I had it opened to clean it. The manual shows different heights for different sizes - all they change is the height of the grids, the center rod, and the top tank. Look at the exploded view on page 9. The parts list shows the grid heights.

Or, less accurately, measure height of filter. Add height of top tank. That tells you how high you'll need to lift to clear the grids inside. Compare to Table 1 in that link to the manual.

 

[Mr. Blue]

I had the same problem when I started.

What I did was measure the height of the grids when I had it opened to clean it. The manual shows different heights for different sizes - all they change is the height of the grids, the center rod, and the top tank. Look at the exploded view on page 9. The parts list shows the grid heights.

Or, less accurately, measure height of filter. Add height of top tank. That tells you how high you'll need to lift to clear the grids inside. Compare to Table 1 in that link to the manual.

Awesome. Thank you!

I am in the process of deep cleaning the pool. I have taken the filter out and cleaned it once when I first started; I am going to do it again once I am done. I can measure the height of the grids then. Below is what the pool looked like when I started. It is now blue and cloudy...just a little bit further to go!