Pool Filter Sand 101

Pool Filter Sand 101

Sand filters are the most common type of pool filter in America, and for good reason! They are efficient, powerful, and relatively easy to maintain. However, changing the media inside sand filters can be somewhat challenging and time consuming. In this article, we discuss when, why, and how to change pool filter sand, so you can keep your sand filter in top shape!

Why Change Pool Filter Sand?

  • New sand has sharp, crisp edges that stack well into layers. Old sand has rounded edges that don’t filter the water as well.
  • Oily dirt, dead algae, and other gummy residues build up and are pushed deeper into the sand bed with each backwashing.
  • Small amounts of sand can be lost during backwashing, and over many years time, can add up to a considerable loss.

When to Change Filter Sand

This depends on the size of your filter in relation to the pool, but somewhere between 2-7 years. Above ground sand filters of 16″, 18″, or 21″ in diameter often need fresh sand more often, every 2-5 years. Sometimes smaller sand filters need new sand sooner if the pool is used heavily, has sticky tree debris, or has a pump that is too large for the filter size.

Larger inground sand filters with 24″ to 36″ diameter tanks can often go longer between sand changes, simply because of the larger filter area. 5-7 years is the normal interval for larger sand filters.

The best time to replace sand is before you need to, meaning before the sand gets worn out and stops filtering as effectively. If you notice poor water quality, short filter cycles (time between backwashes), or dirt passing through the filter, it may be time to replace the pool filter sand.

What Type of Sand Do You Need?

filter sand

Masonry sand or play sand won’t work in a filter, use only a high quality pool filter sand. Pool filter sand, is specifically graded silicone quartz, .45-.55 mm in size, otherwise known commercially as #20 silica sand. You will find it to be clearly labeled pool filter sand.

Our help files also have a few entries of folks who purchased a cheap product ($5) labeled filter sand, that turned out to be a very poor substitute. Buying a well known brand of pool filter sand from a pool retailer you trust may make a difference in the quality and cleanliness of the filter sand you buy.

How Much Sand Do You Need?

Sand filters are not filled completely full of sand, but only about 2/3 full, to allow “Freeboard” space in the tank, above the sand bed. Your manufacturer will list the amount of sand required on their website, usually on the brochure or spec sheet, or you can find it with a quick google search with your filter make/model.

You need to know the tank diameter, which is often reflected in the filter model number, or can be found on the manufacturer spec sheet. Or you can measure the tank with a ruler.

How to Change Pool Filter Sand

How to actually change the filter sand – that’s a whole other topic that we talk about here.

You may also be interested in this article about how to improve sand filtration, or information about pool filter sand alternatives like ZeoSand or FilterGlass.

28 thoughts on “Pool Filter Sand 101

  1. Our filter sand has never been replaced – this will be my first time doing so. When is the best time…at closing in the fall or before opening in the spring?

    • Hi Grant, I would wait until spring, because I’m a procrastinator! But also you could do it now. There really is no best time to change the sand.

      • The girl at the pool place seemed to think that spring would be best since the filter tank would have been emptied for winterizing and therefore the sand would be dry. Make sense?

        • oh, yeah I get it, didn’t think of that! That is a good reason for doing it in the spring, yes. Dry sand would be a bit easier to scoop out, or easier to use a shop vac with, yes thanks for the tip!

  2. Hve a pool 24×48 above ground pool how many bags of sand does it take to put in the pump

    • Hi Mike, check the label on the filter tank, or look in the owner’s manual. Every filter is different, but there is an exact amount for your filter. Be sure to use #20 silica sand, labeled “pool filter sand”.

  3. Daniel Sullivan

    What size sand filter for a 16×24 4ft above ground pool?

    • Hi, your pool has about 8000 gallons or so. You could use the Hayward VL 13″ sand filter, or the Intex 14″ or 16″ sand filters, or the Raypak or Hayward 16″ filters. A 16″ filter will give the best performance over the long term and won’t require as much maintenance or sand changes.

      • I have a 1.5hp hayward pump for my 20 ft above ground pool. What size sand filter should I use.

        • Hi Missy, assuming a 1.5Hp Hayward Powerflo pump or similar, I would recommend the 21″ sand filter, like the Hayward S210T. Oversizing to the S244T would be a good idea if possible for your budget. The bigger the better, with pool filters!

  4. Mehmed Zekic

    Hi,
    I got a new Daytona 4vmp1 filter with a 2hp Hayward I keep getting sand in my pool. You don’t see it entering but after few day with the pump running you can see and feel some sand on the bottom of the pool.? Too much sand ? 2hp to much for the filter ? Should I use pea gravel at bottom of the filter ? Please help if you can.
    Thanks
    M.

    • Hi, yes the Dayton filter has a GPM rating of only 47.5 GPM, and your 2-hp pump may be pushing double that amount. A bypass could be constructed, with a 3 way valve, to allow half of the water to bypass the filter. It could also be too much sand, I don find the required amount.

  5. I’m going to be purchasing a 24×54 above ground pool. I am curious if a 19 inch one and a half horsepower is enough? Also I’m not sure what the difference in the 19 in in the 22 in tank makes on difference?

    • Hi Jessica, the 19″ would be suitable, but the 22 would be better. The larger filter will allow for longer filter cycles, or time between cleanings, and more importantly, will provide better filtration, because it has more sand, and the sand will last longer. It may actually save money in the long run, in decreased filter run time or fewer chemicals needed, because it filters the water more effectively. If you can swing it, I’d always recommend a larger filter, every time.

  6. Haley Gore

    Can I use 2 different brands of pool sand in the same filter?

  7. Crystal Burt

    1yr old Calvin 19″ filter and 1.5hp pump. Pool water is green even after chemicals added. Should I change sand??

    • Hi, probably not needed (new sand) after only 1 year on that size filter. I would look closely at pH level and chlorine level. Get pH to around 7.2, and get chlorine level to 10-20 ppm. Be sure to run the pump 24/7 during this period, and backwash only when pressure rises at least 5 psi. Just keep adding until the water turns a blue grey color, which will be more shock than you have added already. Clarifier can be used after killing the algae with high levels of chlorine.

  8. Kim Wuelling

    Hi. I have a 28 round above ground bought a.new pump filter dial and changed the sand. My pressure is good but after about 15/30 mins it slows down and my gauge is reading 20/30 psi it runs T 10psi after backwash and rinse. Help

    • Hi Kim, I would guess that either 1) the sand is not ‘Pool filter sand’, or 2) the proper amount was not added, or 3) soon after adding the sand an oily substance, or foreign material entered the tank and clogged up the works. If #3 is suspected, you can try a Sand Filter Cleaner product. Good luck!

  9. Richard A Moe

    I bought a intex 3000 GPh sand filter/pump for my new 18 foot round pool and foot high above ground pool. How much sand do need to buy?

  10. My 18 in Hayward sand filter runs for 15-20 minutes and then seems to lose pressure. I backwash and then it will run for 15-20 minutes. This doesn’t seem normal? How do I fix this?

    • Hi Chris, sounds like you need to replace the filter sand, or deep clean the sand with a Sand Filter Cleaner.

  11. Hi,
    I have to put two types of sand in my filter how do I layer them.

    Thank you

    • Hi Louise, two types? Is this a slow rate sand filter from the 1950’s? Modern sand filters need only one type, #20 silica sand. Large sand filters of modern area can benefit from adding pea gravel first, just enough to barely cover the laterals, and then fill the rest with #20 sand – but I’m not aware of other types of pool filter sand, only #20, graded to 0.45-0.55 mm, and always labeled clearly “Pool Filter Sand”.

  12. Ray Gillespie

    My Shott sand filter with multi port is losing sand into the pool every day.
    I have had the pool about 7 years without changing the sand.
    Cleaning the pool via the waste valve only helps for a day or so.
    The pool and filter system was installed by the previous owners so I don’t know the actual age.
    Have you any suggestions please?

    • Hi Ray; sounds like you need a filter overhaul. Is Shott the brand name, or are saying your filter is ‘shot’? Ahh, I just googled it, an Italian sand filter – http://www.shott.it/en/linea/sand-filters/ – so if sand is coming into the pool, what you need are new filter laterals, and/or a new standpipe. These can usually be purchased together, in a set or assembly, but sometimes sold separately. Secondly you would need new filter sand. Drain the tank, remove the valve (cutting pipes if needed for topmount), scoop out the sand, rinse out the tank, replace the broken parts, replace the drain cap, add water to fill halfway, fill with #20 silica sand or filter sand alternative to recommended levels, usually about 2/3 full. Reconnect the multiport, (tip: use unions for future access), start up the filter on the Rinse setting at first, then go to filter. You can buy filter sand locally, I’m not sure where to get Shott parts, might have to order from them, or thru their distribution network.

      Alternatively you could replace the entire kit and kaboodle with a similarly sized Hayward or Pentair sand filter, https://www.intheswim.com/c/filters

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