Diy Non- Pressurized Sand Filter for Backyard Pools





Introduction: Diy Non- Pressurized Sand Filter for Backyard Pools

i have had a few cheap backyard frame pools, and pretty much the "filtration systems" they come with are only good for people that never get in there pool dirty, have no friends, no kids, no dogs, nothing but time to wash or replace the filter constantly, always keep the pool covered, you get the idea.

my pool is a 16' round 42" deep.  think it holds about 4000 gallons. basicly between all the people, and our 2 filthy dogs, the little cartridge filter was not cutting it.  it hangs in there for the 1st couple weeks then the water just gets too nasty. even though i come home and sray it off every day and change it once and a while.  the filtration setup that comes on the pool should probly only come on somthing with a few hundred gallons. whatever, i think it sucks. in the picture obviously im also dealing with some algae.

Step 1: The Basics

why do you want a sand filter? because sand is actually a really good filter, thats why most larger pools and aquatic facilitys and even your nicer backyard above ground pools use them. 

how do they work?  well its actually really simple. a "normal" sand filter is a sealed container half full of sand, water is forced though the sand by the pump. ya its that simple. 

how exactly?  a pump forces the water into the top of the container, usually through somthing that spreads it even so its not just a jet of water blasting a tunnel in the sand, you want a nice even sand bed the water has to go through. in the bottom there is somthing that usually looks like a a bunch of little pipes with slits in them the sand cant fit through that connect to a big pipe, that is the outlet where clean water comes out.

Step 2: Parts

i didnt really document this very well but its pretty simple.

because i dont have any big pump, or larger container with a water tight lid, i used a plastic 55 gallon drum i got free.

i re-used the little pump that came with the pool to get the water into the top of the barrel, i drilled and taped the barrel with 1" NPT pipe thread and used cheap grey pvc barbed fittings to connect the hoses.  

the lower white hose that used to return to the pool now connects to my "spray bar" in the other picture, this evenly spreads the dirty water over the sand.  this is made of 1" PVC with holes drilled in it, i put a union on it so it can be easily removed to ad/remove sand etc.

the clear re-enforced hose comming out the top is just an over flow of unfiltered water back into the skimmer/pool.. more on this later

Step 3: Rest of the Parts

now you want somthing that will stop the sand from comming out and only let clean water through.  for this i used 1 1/4 pvc with lots of slits i put in it using my miter saw, then i covered each bar in cheap lawnscaping fabric and held it on with zip ties, this isnt on there yet in the picture.

i re-used the pump from last years pool for the return pump pumping the filtered water back into the pool.

as you can see i didnt use a whole lot of sand, about 4 bags of play sand, just enough so there a few inches of sand above the suction bars (there called latterals in a real filter), i started to fill it more but it seemed to slow the flow down too much (weak pumps) ended up using 4 x $3.50 bags of play sand.

the overflow:  this is also why there is an overflow on the otherside... like all half assed backyard built sht theres usually some kind of design flaw, this one was the fact that i used the same crappy little pump on the in and out side of the filter, the pump on the skimmer pushing water into the filter has much less resistance and therfor can flow more water, filling the barrel a slightly faster then the lower one can drain it and push it uphill into the pool, against the water pressure of the water already in the pool. 

the simple solution would be a higher flowing pump on the return side to the pool, with a valve if needed for adjustment so it didnt empty the barrel too fast either.  i dont really have the spare $$ for this project right now , maybe i can get a bigger pump later.

option two would be to put the barrel up a few feet on somthing and let gravity assist.

Step 4: Hows Did It Do?

how did it work?  well the water was green and cloudy and you couldnt really see the bottom of the pool, and there was a slimly layer (probly from the damn dogs) and it kind of just smelled no matter how much chlorine was in it.  within a few hours it was noticeably less green, and you could see the bottom again (see picture above)  within a couple of days the water actually looked pretty good the bottom of the pool just needs a vac. I did ad some algaecide but i never had it work this well, or much at all, so i give credit to the filter.

keep in mind i have the flow restricted * on the in side via the over flow wasting unfiltered water back to the pool and not many holes drilled in my "spray bar" because the water does not come out of the pump returning it to the pool very fast. better pumps would really kick some ass.

 I had to backwash the filter once or twice after a couple days, just like a real sand filter you would reverse flow through the filter washing the sand and whatever has settled on top. DO not pump that back into your pool obviously, i just disconnected the hose from the IN side of the filter and let the filter spill the dirty water out and flipped the pump from the OUT side of the filter around so it was pushing back into the sand.  it looked NASTY like the container from an outhouse. 

a normal sand filter would have a multiport valve that makes back-washing easy. its kind of a hassle on my version.

you could even make one of these with a 5 gallon bucket, not sure how well it would work but it would probably work better then the filters that come in these !



    • Make it Move Contest

      Make it Move Contest
    • Woodworking Contest

      Woodworking Contest
    • Oil Contest

      Oil Contest

    We have a be nice policy.
    Please be positive and constructive.




    So on the pump thing, I've seen a lot of people on craigslist or at flea markets and stuff that have hot tub pumps, in working shape, for like, super cheap. Might be a good source for a pump that will move a little bit more water if you get the right one.

    I'd love to see someone make one out of a five gallon bucket and some pipe. Maybe you could put it directly under the skimmer and pipe it directly into the lid? A couple ball valves and some tees for back washing?

    1 reply

    The big problem with doing a 5 gallon bucket is just going to be the surface area of sand that you have available to filter. There are some calculations that we do on commercial pools that tell you how much sand you really need- you might even be able to do something where you run multiple buckets, but it's pretty important to make sure that you have enough surface area to filter the amount of water you are dealing with.

    how powerful IS the filter you used? (so anyone doing this project can avoid that pitfall by buying a stronger one)

    I know this is an old instructable, and you've probably refined the filter a bit by now, but do you even need an "in" pump? if you have a direct connection to the pool, with no possible airlocks, the level of the water in the filter should stay the same as in the pool, the water just flowing naturally into it. I'm planing on making a filter for grey water before it goes onto the garden (just to reduce any smells), and I was thinking "gravity sand filter" and found this... mine will probably need gravel to avoid the "blast through the sand" effect

    my neighbor had a big 1 horse pool pump..........................I got it for......................$5 WHEN HE TOLD ME THAT I WENT RUNNING FOR MY MONEY BEFORE HE COULD CHANGE HIS MIND

    I like your ingenuity. This a great solution, for your pool and it also has real application to fish pond builders as well. Sand filters reallly do an excellent job. The use of the overflow pipe is clever; the pump is really underpowered. A suggestion is to make use of some hydrochloric acid to buffer your pool and keep the algae down. This will reduce the chlorine required. Check the pH frequently. Even with two dogs, your approach will pay off with crystal clear water.

    4 replies

    Bleach can be used too, as long as it's a chlorine base, just dont pour it in raw, (same with the acid by the way) or it will sink and decolour the liner if you don't dilute it first!!

    you can put bleach in the pool with out diluting it first i i do it all the time and its more effective

    wont hurt any thing really the water in the pool dilutes it any ways


    Using hydrochloric acid has several benefits - just think of it as ultra fast acting chlorine (HCl = Hydrogen + Chlorine!) : It gets the pH down fast as it is an acid, it's the fastest acting chlorine you can find (great when you have to superchlorinate an algae infested pool) and it's a darn sight cheaper than using buckets of chlorine tablets!

    I cannot remember what our equivalent doses my stepdad used though (20 odd years ago!), but Google will help you find it for you!


    yes those tablets are expensive. the bucket pictured in the backround was powdered chlorine shock i got for free at work because some one ordered lithium shock and i dont like using that in the pools at my building. i normally just buy liquid pool shock and throw some stabilizer in

    bah, remove the chlorine and put in some fish, they'll eat the algae and any insects that land in the water.


    motion blur / crappy phone camera


    If you have outdoor dogs that like rubbing themselves over the grass, then you will get a green pool :) I've seen the colour of the water when my mom managed to catch and shower her mutt ;)

    If you were using a cartridge filter, whatever the size of the pool, you will end up with a green pool unless you declare chemical warfare on it - the pores on the filter are still to big to filter out the smallest algae, and even after superchlorinating the water, and everything is dead, the filter just cannot take the crud out of the water!

    My parents ended up getting a 6000 gallon-ish pool complete with a sand filter, though the pumps have a tendancy to die after a few years - and given the price of a pump and filter system, compared to yours, this could be a great replacement idea.

    A question; do you have a method on hand to flush the filter? - push a couple of dozen gallons of water the "wrong way" through the sand, and dump the outflow (don't pump it back into the pool whatever you do!), so it resettles the sand - and the backflow will flush a load of crud out from the sand and refresh the filter!

    1 reply

    yes i do "backwash" the filter, i take the pump on the clean side of the filter, flip it around, disconnect the plumbing on the dirty/water in side and let it hang so it pumps water through the filter in reverse. it usually looks NASTY. then i put it back and let the water flow through the normal way a few minutes until the sand settles then hook it back up

    Great and useful work, thanks for sharing.


    thanks for the compliment and your right, im actually a certified pool operator, i just dont care, i dont want to spend alot of time balancing my crappy backyard pool when i do it all day at work. i just want the water to look clean