Sand Filter media

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J

Jonsstihl

Well-known member
Sep 2, 2021
81
Quebec, canada
starting my second full season with the pool and had a question about pool filter media. The company that installed my pool used gravel in the filter. it is actually written filter media on the bag so i think it is actually designed for this purpose but i was wondering what you guys think of this.
I have no filter problems yet.
I had no trouble opening my pool last year. this year had a green mess started a slam. got rid of the green fairly quickly once I hit it with chlorine but the cloudiness took forever, atleast a week.

i did put some DE in the filter this weekend and it has cleared up nicely. I will continue doing that but I'm not sure if it is the gravel that just isn't as good as sand at filtering.

I drain my pool with the backwash setting from the floor drain so I'm assuming my filter is pretty clean but will probably do a deep clean at some point. filter pressure starts around 12 PSI after a backwash.
 
A layer of gravel and then a layer of sand or is it just filled with the gravel material??

It’s not uncommon with certain sizes of sand filter (larger ones) for the manufacturer to call for a gravel bed on the bottom around the laterals and then to fill the rest up with sand to the freeboard level. Doing so usually improves the flow rate and head loss of the filter a bit. But it’s should not be all gravel.

I would scoop some of the media out of the filter and check the size. It should be #20 sieve silica sand.
 
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definitely all gravel. they brought five bags of gravel uses two for under the paving stones and put two in the filter and I have one left over. but I did have a problem at the begining with it requiring back washes every couple of days and the guy that came to check it had the top of the filter off before I could get my shoes on but I don't think he added sand but the problem went away. I think it was a problem with low FC and ammonia taking away my CYA. I got a test kit at the begining of the next season and haven't had a problem with too frequent backwashes since.
 
Jonsstihl said:
definitely all gravel. they brought five bags of gravel uses two for under the paving stones and put two in the filter and I have one left over. but I did have a problem at the begining with it requiring back washes every couple of days and the guy that came to check it had the top of the filter off before I could get my shoes on but I don't think he added sand but the problem went away. I think it was a problem with low FC and ammonia taking away my CYA. I got a test kit at the begining of the next season and haven't had a problem with too frequent backwashes since.
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How big is the filter? Mine took many more than 2 bags to fill. Sounds like the bags are extra large in Canada, or your filter is extremely small, or they didn’t put enough sand in the filter.
 
Jonsstihl said:
Any one have any idea how high the media is supposed to be in the filter. I'm assuming around half way up. i know it shouldn't be up to the top. It's just hard to picture what 4 bags of media would look like in the filter.
Click to expand...

Every sand filter has a “freeboard” distance from the top of the filter to the sand bed. It’s usually not halfway. You have to look at the filter manual or call the manufacturer to find out what that distance is.
 
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definitely all gravel
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That's a mistake.
A 19" filter should be all filter sand or perhaps some washed gravel up to the laterals, then sand to the freeboard height..

If you can't find the "freeboard" dimension, you will be VERY close filling it 2/3 full,
 
I sent them an e-mail just now. Their filter technical specs only list the weight of sand that should be added. I currently don't have any filter problems my backwashes are about once a week. It did take a long time to clear the water after my SLAM but that was the first time for me so I have no baseline. It took about a day to get rid of the green and about a week to get rid of the cloudiness.

one thing i did notice yesterday is that just turning the pump on and off to clean the skimmer and pump basket dropped the filter pressure back to my baseline and I was almost due for a backwash.
 
Jonsstihl said:
I sent them an e-mail just now. Their filter technical specs only list the weight of sand that should be added. I currently don't have any filter problems my backwashes are about once a week. It did take a long time to clear the water after my SLAM but that was the first time for me so I have no baseline. It took about a day to get rid of the green and about a week to get rid of the cloudiness.

one thing i did notice yesterday is that just turning the pump on and off to clean the skimmer and pump basket dropped the filter pressure back to my baseline and I was almost due for a backwash.
Click to expand...
Once a week? Yikes. Mine can go all season without backwashing. My filter manual says that they have generic baseline for weight but that since different material weighs differing amounts that you have to go by the dimension they say to.
 
Interesting conversation about "free board" - anyone know the free board for a Hayward S244T filter. I load it with 300 pounds of #20 - but never checked the free board space - I would be interested to know how many inches it should be and where you measure the distance to from the sand bed?
Thanks!
 
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