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Diy non- pressurized sand filter for backyard pools

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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.

 
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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.
flamesami5 days ago

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

muddog151 year ago
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
cobourgdave2 years ago
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.
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!!
rbennett8 bpfh1 year ago
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!
7808 (author)  bpfh2 years ago
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
shakeval1 year ago
bah, remove the chlorine and put in some fish, they'll eat the algae and any insects that land in the water.
LucDaRocka12 years ago
Do you have a deformed dog in that Picture?
7808 (author)  LucDaRocka12 years ago
motion blur / crappy phone camera
Oh, okay IM A DOG LUVER
bpfh2 years ago
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!
7808 (author)  bpfh2 years ago
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
rimar20002 years ago
Great and useful work, thanks for sharing.
7808 (author) 2 years ago
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