Want to build a raised platform for a 550 gal plastic water tank

I'm looking to build a raised water tank platform.

550 gal plastic water tank about 3 foot tall

Predominantly clay soil

Only for use in non freezing weather.

Would like to have the platform maybe 4  feet tall to gravity feed but don't need to have much water pressure.

Any suggestions on design or materials? We have hand tools but and battery operated drills and saws and such but nothing much else.

Thanks

Hi Penny! Your platform design is going to need to be pretty stout to support the weight and prevent an accidental collapse. If that 550 gal tank is full, it will weigh approximately 4400lbs, along the lines of an automobile. I think you can build a platform with the tools you mention. If you’re going to be purchasing lumber for this project, I suggest 6x6 for vertical posts to carry the load. The structure of the platform can be made with the same material, and all put together with lag bolts. It is important to notch the vertical posts so the cross members sit on a small ledge (like in lap joinery) so the wood structure is carrying all the load and the lag bolts only just hold things together and aren’t carrying any weight. Here’s a picture of what lap joinery looks like. Hope this helps you figure out a plan!

If it's only going to be 4' off the ground, I think you'd be fine with 4x4's for the legs.  As long as they are sitting on nice pads so they don't sink into the ground.  They make cement pads shaped like an octagon that would work.  

Does the tank have a flat bottom?  I'm guessing you'll need to support it with a lot of cross members or a floor.

I'd start by making the four legs and notching the top like James says.  Use 2x6's for the cross pieces between the legs, flush to the top.  They need to be on edge (vertical), like when you build the support for a deck.  I'd probably use joist hangers (metal brackets from the hardware store) and attach more 2x6s on probably a one foot spacing all the way across the platform.

Then if the tank can sit on those joists, you're good to go, if it needs more support, run 2x4s across the top of the joists like deck boards.  They could be spaced a few inches apart to save money.

The legs also need to be significantly braced so that the whole thing doesn't fall over.  So diagonal 2x4s connecting the tops and bottoms of several of the legs is in order.

If your tank is a potable water friendly IBC tote,  I suggest looking for a second tote, that is to tainted to ever store potable water in.
These totes are a lot cheaper than the other ones,  and one will give you 3' of height.
Totes are designed to stack 3 high,  so the weight wouldn't be an issue.
To make up the rest of the 4' maybe stack pallets 3 high under the bottom tote.
Come to think of it, a stack of 10 pallets, atop  a foundation  of cinderblock,  could work just as well.
Maybe drive some U stakes  alongside the closed sides of the pallets, then screw them into the stringers.

Since it's 550 gallons, I was assuming it wasn't an IBC...  But that would make the platform easier since they only need support around the perimeter.

Another option is to use cinderblocks as the legs.  Start with a good flat gravel surface and dry stack them 6 high and you have 4'.  Or mortar them to build some low risk masonry skills.

Or use cinderblocks as the whole platform.  Just make a series of 4' high rows of the blocks until they cover the footprint of the tank.  They're cheap and strong.

Thanks so much for all your input.

Yes, it is a round 550 gal water tank but I am really intrigued  by the icb support idea.

We have a couple of those that are in use right now for other things but I didn't realize that they were built to be stackable. Makes sense though.

Ours are 3' x 4' on top and the bottom of the round tank is 64" in diameter so if we did 3 icb's or even just the frames of them with some sturdy floor over them to provide a solid base for the tank, I think we would be all set.

Awesome, thanks so much.

We support our icb with railway sleepers, two one way then two the other way cut to length. stack as many as you want just got to make sure the bottom two are level and on solid ground.

Skandi Rogers wrote:We support our icb with railway sleepers, two one way then two the other way cut to length. stack as many as you want just got to make sure the bottom two are level and on solid ground.

I love it. Sometimes the simplest ways makes the most sense.

Is it feasible/reasonable to build some kind of berm or mound with soil to raise the tank?  Dirt is pretty inexpensive....actually, it's dirt cheap ;)

Don't know that the rail way sleepers would work since our 550 gal tank is the round plastic kind and needs pretty consistent support across the entire bottom.

Dirt would be an option except that ours is clay and dried solid like adobe brick right now. It would also need to be packed down fairly solid so that the tank didn't start to tilt when the weight of the water started to compress it. And it would probably need to be a fairly big mound since the tank is 64 inches across and at 4 feet height it would either need retaining walls or to be quite a bit bigger at the bottom so that the dirt wouldn't just sluff or erode  away from under the tank.

So IBC totes are designed to stack on one another since their frames can carry the weight through the cage (as I understand it).  So when you go to put your round tank on top of the IBCs, I'm thinking you'll want a series of boards for the tank to sit on that can spread the weight onto the frames of the IBCs.  If you just set the tank on IBC, the tank bottom will be only seeing support where the frames of the IBCs touch it which may not be enough.  Maybe.  I think...

I have raised some heavy tanks on simple stacks of concrete blocks, with a metal fence stake or two driven down through each stack to hold them straight, and then miscellaneous scrap lumber and plywood laid on top to make a rough platform for the tank.  Basically used what I could scrounge, so as to buy nothing but the tank and it's plumbing....

Yes, I was planning on a couple of pieces of sturdy floor to spread the bottom of the tank on the icb's.

If you built a soil pile for the tank to sit on, you would need to put a layer of sand or fine gravel, levelled out for the tank to sit on.
Also, if you have access to a welder, a simple tank stand can be built with 4 posts, bracing and cross bars.
Fit timber across the top that is suitable and it will last for years if set down onto concrete pads.
Tank stand image

I have also seen rings of steel or bricks which are filled with soil and used as a stand.
4 feet maybe a bit high though

Hey All,

We just finished the same project earlier this spring. 1000G tank, 4' off the ground.  We used used regular treated fence posts (3-4" 7 foot) sunk 3' in the ground topped with 6x6 spruce beams and decked with 2x6.  Has been fully loaded for the last 3 months with no sign of shifting.  We actually just made a video of the whole off grid gravity water system, you can check it out here:



And a few pics.... wait, how do I insert pics??  I'll get back to you with the pics.

Jeff and Rose

i loved Jeff and Roses version... cute and funny!!! Plus we are almost neighbors, Me SE Alaska, them Northern BC.. only 1 country apart

Penny McLoughlin wrote:Don't know that the rail way sleepers would work since our 550 gal tank is the round plastic kind and needs pretty consistent support across the entire bottom.

Crib stack railroad ties as suggested but put a bunch of them up against each other on the top level for a floor.

Four key principles you'll need to think through.

First, ground stability.  For something that heavy, your structure should probably be dug into the soil at least a foot or more, because topsoil has a lot of organic material in it that will continue to decompose and thus, the structure will settle, tilt and shift.  If it were me, I'd excavate down at least 2 feet, and then backfill with crush-grade road mix (fairly inexpensive).  That'll give your base stability.

Second, contact with the soil.  Unless treated, any wood in contact with the soil will eventually rot.  You could use pressure treated timber, but that will eventually leach some pretty nasty stuff into the soil over the years.  People have suggested railroad ties (sleepers) -- also treated heavily with creosote.  I don't want that anywhere near my garden.  The half-life of that stuff is a zillion years, which is why they use it on railroads.  So if you're planning on using them, I would get them up off the soil by using concrete blocks.

Third, lateral stability.  Even 4 feet of elevation needs to be laterally supported with triangular supports.  A triangle (three beams lagged together with steel hardware) is tremendously strong.  If you look at pictures of elevated water tanks for things like old time train stations or farm water tank storage, they have all sorts of supports that not only go vertical and horizontal, but diagonal, to tie the structure together.  That will keep your structure from racking or twisting under the weight of all that water.

Finally, I'd make sure you have a solid base under the tank -- not just joists.  Exterior grade plywood will eventually degrade with moisture unless it's properly sealed with some sort of membrane over it.  You could make something solid with 2by material -- but wood, unless treated, will eventually fail.  You could pour a 4" slab on top of your support structure, using lots of re-bar.  That'll add considerably to the overall weight.

If it were me, I'd dig 5 holes (a square with a center post to hold the middle of the structure), and backfill with at least a foot of crush grade.  Then I'd use those cast concrete pier supports with the steel bracket to bolt hour legs on.  I'd use 6 x 6 posts, pressure treated and angle them slightly inward, so that the base of your structure is slightly wider than the tank itself.  Using lateral supports to keep the legs from walking outward, and diagonal cross-braces (to keep the thing from racking), I'd use at least 2 x 6 material for your braces.  2 x 8 would be better.  

For hardware, I'd use bolts with nuts and big washers (on both the bolt side as well as the nut side) rather than lag screws.  If using pressure treated wood, it's best to over-drill the holes slightly, and then squirt paint into the holes.  The chemical they use for pressure treated lumber is chromated copper arsenate (CCA).  It can be corrosive to steel hardware over time.  By coating the inside of your holes with paint, and then by also priming and painting your hardware, it mitigates future corrosion.  You can spray-paint the bolts and washers with Rustolium.

For the frame at the top of the structure, I would use 2 x 8's on 1 foot centers minimum.  On top of that, 1" exterior grade decking plywood, and on top of that, glue down a weatherproof membrane that is rated for exterior deck application.  They sell this stuff by the roll.  Wrap that membrane over the edge of the structure so that water will not pool on top but will drain off.  You need to protect the edge of the plywood.

I would paint it with at least 2 coats of oil based primer, and then 2 more coats of latex exterior paint.  THEN I'd put my tank up top.

Overkill?  If you do it right the first time, you'll never need to mess with it again ever.  A structure like that would be good for 50 years.  At this point in my life, I don't have the time or patience to go back and try to fix things that were under-engineered to begin with.  Yes, building it right the first time costs more, but in 10 years when that structure is working perfectly and your tank hasn't budged an inch, you'll be glad that you took the time to do it well.  At least I look on stuff like that with a sense of craftsman's pride.  

One final thought: you could build it in such a way that you could store stuff underneath it.  Enclosing the sides and adding a door, it would be a great place to store hoses, tools or whatever.  

Best of luck.  Send pictures.

@Marco

is it true you guys down here in your neck of the asphalt woods are not allowed to harvest rainwater if it was to rain?

Mark Figelski wrote:@Marco

is it true you guys down here in your neck of the asphalt woods are not allowed to harvest rainwater if it was to rain?

I've never heard that.  They sell rain barrels in the hardware stores -- obviously for use in capturing rain water.

Los Angeles passed a big tax measure last year to slowly re-engineer the city toward the goal to capture, store, use and infiltrate rain water.  Basically, we are now taxed based upon how much hard water-shedding surface you have on your property (sidewalks, driveways, concrete patios, etc.).  It's not a huge tax, but over time, it will fund projects intended to capture and hold water throughout the Los Angeles basin.  If you wish to lower your tax burden, remove concrete.

This is a massive city and an even bigger county -- it's hard for people to get their head around how big LA county is.  There are 108 cities in Los Angeles county.  My city is only 65,000 or so but its one of a hundred, most of which are much much larger than my suburb.  Los Angeles has over 4 million residents.  The entire county has about 10.5 million people.  That means that if LA county were to be a state, there would only be seven states larger (California, Texas, Florida, New York, Illinois, Pennsylvania and Ohio).  The goal over the next 50 years is to re-engineer roads, roofs, parking lots, riverbeds . . . and keep the rainwater in LA rather than drain it off as quickly as possible into the ocean.  Its going to be a massive undertaking.

I think you'd be surprised how much land there is in greater Los Angeles that is still "wild".  We've got coyotes running through our yard at night, among all manor of other critters (raccoons, possums, squirrels).  I've never seen a deer or cougar in our neighborhood, but they are out there. Every so often, you'll see news footage of a bear up in Pasadena or one of those cities up against the hills.  There are ducks by the millions, some of which find my pool to be exactly what they are looking for as they raise their ducklings.  The entire LA basin is surrounded by hills -- think Beverly Hills, but that is just on the west side.  Orange County, to the south is hemmed in by hills, Ventura county to the north, again, lots of hills with undeveloped canyons . . .  There is still open space where wildlife lives.  That's why so much of it continually makes its way down into the city, to the lush green lawns and golf courses.  

With that as a goal, there are plans to help homeowners capture as much rainwater as possible and infiltrate it into the ground rather than drain it out to the street.  So no, there are no laws against capturing and using rainwater.  Just the opposite.