Old filter sand - up close!

chjade84

Well-known member
Apr 2, 2014
106
Indiana
I think it's time for new filter sand? My PSI climbs from 15 to 20-25 in a matter of days, and my water is quite clean. I just did the deep clean last night and noticed my sand has been warn down into tiny smooth spheres! I don't know how old it is but I brought a sample into work to take a look at under the scope and share with you guys here.











On a side note, what does the air relief tube do? I pulled it out to get the diffuser off last night abut just kinda stuck it back in when I was done. Where is the end of the tube supposed to go?
 
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duraleigh

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We never suggest changing the sand. It comes to you millions of years old already so 20 years in a pool has little affect.
My PSI climbs from 15 to 20-25 in a matter of days, and my water is quite clean.
That simply means your sand is catching particles and the particles are adding resistance to your system.

Posting a complete set of test results is the first step but your water is not perfectly clear or you wouldn't have the psi increase.
 

chjade84

Well-known member
Apr 2, 2014
106
Indiana
We never suggest changing the sand. It comes to you millions of years old already so 20 years in a pool has little affect.That simply means your sand is catching particles and the particles are adding resistance to your system.

Posting a complete set of test results is the first step but your water is not perfectly clear or you wouldn't have the psi increase.
I suppose it could be catching the plaster "dust" that was created after the acid wash. I've noticed I can brush the bottom and a bunch of "dust" will get kicked up. My new robot has filters that catch it and I rinse out a bunch of what looks like sand from its filters after every use.

Tests from last night are:

FC: 4
CC: <.5
PH: 7.6
TA: 80
CH: 275
CYA: 15-ish?

I've just added more CYA a few days ago so I'm still waiting on it to register properly. I'm out of reagent for the test though... just waiting for it to get here... ;)
 

JasonLion

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Not really. The dust shouldn't last all that long. Brushing regularly will help clear it up more quickly. While it does last, you just need to backwash more frequently.
 

freqz

Well-known member
Sep 9, 2013
119
Dallas, TX
New sand looks a lot like old sand ;)

Think of sand grains like tiny river rocks...they've been beat to heck for a very long time getting from wherever they came from to wherever they were deposited while getting carried down a mountain then a stream and then a river.

"New" sand:
 

chjade84

Well-known member
Apr 2, 2014
106
Indiana
New sand looks a lot like old sand ;)

Think of sand grains like tiny river rocks...they've been beat to heck for a very long time getting from wherever they came from to wherever they were deposited while getting carried down a mountain then a stream and then a river.

"New" sand:

I guess I was thinking new sand would look more like this "Lumber Yard" sand:



Or this sand from Guam:





But... neither of those are pool grade silica sand. :)
 

woodyp

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Apr 17, 2010
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East Texas
Thanks for posting..........very interesting. Kinda backs up our suggestion of not needing to "change" the filter sand.
 

chjade84

Well-known member
Apr 2, 2014
106
Indiana
The pool grade sand will be a lot closer to frac sand which will typically be pretty 'round'.
Where does the pool sand come from? Why is it round?

- - - Updated - - -

Thanks for posting..........very interesting. Kinda backs up our suggestion of not needing to "change" the filter sand.
If I can get my hands on some new filter sand, we can really compare!
 

chjade84

Well-known member
Apr 2, 2014
106
Indiana
Want me to mail you an envelope full? :p I have bags of it stacked, ready to go into my filter.
Haha surely I can find some around here. Can you imagine what the post office would think about that? Just a letter envelope with a tablespoon of sand in it and nothing else? lol

Same way a river rock is round...
Well sure, but I guess I meant why is this silica sand round while other sands are jagged? Is it more a property of silica or a property of where it is found vs. "normal" sand?
 

chjade84

Well-known member
Apr 2, 2014
106
Indiana
EDIT:

I didn't think as many people would find this as interesting as I did!

So, I took photos with the DSLR instead of the cheap scope camera so you can see the grains in more detail. :)
 

freqz

Well-known member
Sep 9, 2013
119
Dallas, TX
Haha surely I can find some around here. Can you imagine what the post office would think about that? Just a letter envelope with a tablespoon of sand in it and nothing else? lol



Well sure, but I guess I meant why is this silica sand round while other sands are jagged? Is it more a property of silica or a property of where it is found vs. "normal" sand?
It all depends on how long/how far it took to get from where it came from to where somebody dug it up. Some application you want more angular sand, for some you rounder sand. Filtering is one of those instances where you'd prefer the rounder variety. (angular pieces fit together in weird ways and could make your filter either too permeable or not permeable enough)