Determining amount of DE I should have in filter

Aug 12, 2016
56
Houston TX
We bought a home with a pool and have no idea what the capacity of the filter is. All the labels/external markings that would give us an indication of the size of the filter have weathered away. Is there another way to determine its capacity for DE?
 
Sarah,

A couple of thoughts..

1. Send us a picture of your equipment pad, showing the filter. Two pics from different angles would be best. We need to be able to tell what size and brand the filter is..

2. If you have not done so yet, it would be best to open the filter and completely clean it out, so that you have a known starting point.

3. Most DE filters have a valve that allows you to backwash them. When you backwash you are never able to get them completely clean, so you only add about 75% to 80% of what you'd put in when completely clean.

4. At the top of the filter should be a pressure gage. You will need to backwash, or clean, whenever this gage gets 25% to 30% above the "clean" pressure. This is why I suggest that you start with a completely clean filter, so that you know what the "clean" pressure is.

Jim R.
 
image.jpgimage.jpg

Here are are the pictures of the filter. Sorry for the delay in posting them, I was unable to upload from my phone for some reason. My husband did the complete clean about a month ago, but being pool newbs we didn't know to take note of the baseline pressure.

- - - Updated - - -

Ignore the 3rd pic. Attached in error! Glad it wasn't incriminating ;)
 

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Looks like a Pentair FNS Plus 48 sqft filter, which takes 4.8 lb de. It might be a 60 sqft. The 48 sqft grids are 24" tall and the 60 sqft grids are 30" tall. You will be ok using 5 lb of de until you can take the filter apart and check the grid length.

What is the filter pressure?
 
The high-flow air relief valve on the top is missing. It looks like the previous owner just jury-rigged some kind of metal coupling on top with a pressure gauge. The filter will still operate in that configuration but you really want an air-relief valve on top to purge air that can build up from opening pumps up and what not; they also make opening the top cover easier as you can release any sealing pressure that might develop.

If you post a close up of the top of the filter, we can see better what is there. I don't want to mess with it if the previous owner did what they did to stop a leak. As I said, the filter will still operate, but that's not the most optimal setup...
 
The 48 sqft filter is 49" ground to top of the pressure gauge. The 60 sqft filter is 55" from the ground to the top of the pressure gauge. However, that's with the original air relief. Yours is not the original, but it looks close enough that you can probably use it to determine which filter you have.

Probably best to get a new air relief. It should just unscrew. Is the pressure gauge in the picture accurate? The pressure looks really high.
 
Matt you are right about that. It is leaking a little bit as well and we plan to replace it ASAP. We have purchased the parts to replace the topper with a relief valve and gauge but I am a little nervous about disassembling what is there. I'll take a close up pic of it tomorrow.
 

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