Building a water tank

[vpd66]

Hello, I've had this project in mind for a year or so and have been hoping for something surplus or scrap to turn up, but no such luck. What I need is to build a square tank 5' wide by 6' tall by 7' long. It should hold about 1500 gallons. It will just hold water and it will have a man hole on the top to fill it. It will not be pressurized and it will not be under any pressure and will be open to the atmosphere. How thick of steel should I build it out of? I'm thinking 1/4". Does anyone know how to calculate the weight of water on tank sides? I'm a welder by trade and have no problem cutting and welding the tank. I just need to do the engineering. Back 6-7 years ago when steel was affordable, I would have just built it out of 1/4" steel and if it bludged out the sides to much i would just weld reinforcements on the sides. Steel is just to costly these days for "Redneck engineering". LOL

 

[Artisan]

5x6=30x7=210Sq Feet of water.

1 cubic foot = 7.480 519 480 5 gallon [US, liquid] x 210 = 1570.9 Gallons.

Water weighs 8.34 pounds per gallon x 1570.9 = 13,101 Pounds of water
plus your steel... 13,101 pounds on 5x6= 30 square feet.

13,101 \ 30 = 436.7 pounds per square foot at the bottom for weigh straight
down. I would be more concerned about my bottom I thunk.

Swimming pools are made of really thin metal...it is the frame that does the work, yes?

1 foot of water exerts a pressure of I think .433 pounds per foot so you have 2.59 pounds of pressure at the very bottom if your full, subtract .433 for each foot you empty out of the tank.

Get an engineer to tell you about horizontal forces. :laughing:

I think I might concentrate on a good frame and maybe use 1/8" for the tank with maybe 2" x 2" x thinwall square tube frames bottom, 3 middles and a 3" or doubled 2" top.

Did you think about finding the local farm supply and just buying a cattle water trough? Or maybe just pick up one of these.

 

[mjncad]

I'd just buy a plastic tank and be done with it. No rust to worry about; but algae could be a problem if above ground and exposed to sunlight. However; there are black tanks out there to counter the algae issue.

http://www.watertanks.com/


Or are you just looking to build a tank because you can? If so, go for it.

 

[MarkV]

Considering the cost of steel a plastic septic tank might be more affordable and easier.

MarkV

 

[vpd66]

Plastic is out of the question. The tank is going to be used has a heat storage tank. The water will be heated to 180 degrees. The tank also is custom sized to fit into an already built shed, so the size has to be with in a foot of every dimension. Like I said, I've searched around for over a year and have not found anything prebuilt that would work. I'm sure has soon has I purchase the steel, something salvage will pop up.

 

[vpd66]

5x6=30x7=210Sq Feet of water.

1 cubic foot = 7.480 519 480 5 gallon [US, liquid] x 210 = 1570.9 Gallons.

Water weighs 8.34 pounds per gallon x 1570.9 = 13,101 Pounds of water
plus your steel... 13,101 pounds on 5x6= 30 square feet.

13,101 30 = 436.7 pounds per square foot at the bottom for weigh straight
down. I would be more concerned about my bottom I thunk.

Swimming pools are made of really thin metal...it is the frame that does the work, yes?

1 foot of water exerts a pressure of I think .433 pounds per foot so you have 2.59 pounds of pressure at the very bottom if your full, subtract .433 for each foot you empty out of the tank.

Get an engineer to tell you about horizontal forces. :laughing:

I think I might concentrate on a good frame and maybe use 1/8" for the tank with maybe 2" x 2" x thinwall square tube frames bottom, 3 middles and a 3" or doubled 2" top.

Did you think about finding the local farm supply and just buying a cattle water trough? Or maybe just pick up one of these.

Thanks for the info! I was thinking of building it like you would stud a wall with 2"-3" steel channel for the studs maybe 21" on center and using 1/8" steel skin on the inside of the studs. I've seen quite a few of these tanks built out of 3/4" plywood and 2x6 studs run horizontal around the tank. They used epdm rubber for a liner. I'm a welder and perfer to work in steel then no rubber liner would be needed.

 

[BRBurns]

Swimming pools are made of really thin metal...it is the frame that does the work, yes?

Swiming pools can be made thin because they are round (typicaly).

You will have 2.6psi pressure pushing on the sides at the bottom. The bottom to the sides will be relativly well supported since it will be welded to the bottom plate (I assume). So you will have an average PSI of 1.3 on the entire side. 6048 square inches on the 7 foot side. 7862 lbs pressing on the entire 7 foot side.

It's been too long since college for me to remember how to calculate the load in the center exactly, but I'm thinking that 1/4 steel will bow significantly. However some angle iron going around the top and in an X pattern on it's side would help greatly.

 

[BHD]

Red neck engineer here

fuel tanks are Round. water tanks are round grain tanks are round,

Hum I wonder why?

if you make it round one could make it out of 16 gage, 10 gage would be really over kill.

I have a water tank that is ROUND that is 20 foot tall and 9 feet across it is either 3/16" I believe,

my son make tanks and there rolling out 1/4" sheets into about 10 foot cylinders for the oil company's and welding up tanks,

go to some place that has the rollers and have them roll you out the shell and then weld the seam top and bottom on,

If there is no one with a roller have them break it into segments 10 gage I would think would be more than strong enough. for that size of tank, if round in nature.

IMO

 

[SandburRanch]

For a lot less money than stud wall construction, it could be built similar to the way farm wheat truck sides were kept from bowing out. They had a chain inside ( heavy dog chain size ) from one side to the other with a simple chain binder, attached in which ever link chosen, drawing the sides together . A series of these each direction could be attached to stubs welded about a foot O.C. each way or #2 rebar might possibly be used with some planning.

 

[BRBurns]

For a lot less money than stud wall construction, it could be built similar to the way farm wheat truck sides were kept from bowing out. They had a chain inside ( heavy dog chain size ) from one side to the other with a simple chain binder, attached in which ever link chosen, drawing the sides together . A series of these each direction could be attached to stubs welded about a foot O.C. each way or #2 rebar might possibly be used with some planning.

That's a good Idea. Probably the best bet if he really needs it to be square.

 

[jenkinsph]

If you build this tank in steel which is the likely conclusion I would also recommend a good quality spray on liner. Maybe powdercoat or Demetcoat will work as that would be cheaper than a high purity coating. If you don't do this I think it will rust out prematurely and you would be back to square one. Find one of these tank liner coatings available to withstand 180 F. Since the tank will cost about $2000 to build (rough guess in 1/4" plate) in materials you wan't it to last too.

For bracing I would expect angle iron with a finger turned in to the walls would help support it well enough. Best to have it engineered if possible but I would probably guess if it were me.

 

[SandburRanch]

My non professional engineering mind still has gears turning. 9 gauge galvanized wire laced between eyelets from side to side would probably work. Make the eyelets from chain a dozer stretched. Now we're getting down to budget. :laughing:

 

[tommu56]

A friend of mine has solar hot water.
The company built the tank in his basement out of the fiber glass pool parts bolted and banded together and lined the inside and bottom with foam board. hasd a heavy pool liner made to fit and built a foam cover
It survived fine he moved but it lasted the 10 years I knew him while living there.
They uses copper pipe coils in it for the heat transfer water in the tank never left the tank.

tom

 

[vpd66]

I know a round tank would be the way to go, but even if I had it rolled by someone it would still be multiple pieces to weld up. I don't know anyone with a 19ft by 7ft piece of steel. The largest steel plate I know locally would be 5ft by 12 ft. It would take 4 pieces that size and it would have 5 seams just to make the cylinder. Just try to image trying to get that cylinder welded up. I just think making it square would be easier to build and would elminate having to out source the rolling.

 

[Iplayfarmer]

180 degrees is pretty hot water. What are you going to do with 1500 gallons of 180 degree water?

How important is it that you get all 1500 gallons? The dimensions you gave are about what a small tanker truck would haul (6 wheeler size). I would think you could find a used tank like that for cheaper than materials cost for your tank, but the volume would likely be about half.

 

[vpd66]

180 degrees is pretty hot water. What are you going to do with 1500 gallons of 180 degree water?

How important is it that you get all 1500 gallons? The dimensions you gave are about what a small tanker truck would haul (6 wheeler size). I would think you could find a used tank like that for cheaper than materials cost for your tank, but the volume would likely be about half.

What am I going to do with 1500 gallons of 180 degree water???? Heat my house and shop!!! I would connect it to my wood boiler and that would heat the water. Then I draw off the tank to heat my house and shop. 1500 gallons should let me have a fire every other day in winter and maybe once a week in summer to heat my DHW.

 

[Ted Summey]

I have a 500 gallon water stove to heat 2400 square feet. Here in NC on the coldest days (in the teens) I have to fire it twice a day and more when the wind blows. 1500 gallons in Wisconsin sounds right as an addition to a wood fired boiler. I have thought of adding a 500 gallon storage tank to minimize the number of times I have to fire my stove. There is a company in Mount Airy, NC that builds water stoves which are essentially storage tanks with a firebox and flues built in. It is not a pressure system as it can't be fired above 212 degrees or it will boil over.

A call to Hick's Water stoves in Mt Airy might be helpful. They do build larger water stoves 1000 gallons and bigger. I am sure they are on the internet.

 

[Den1952]

pressure on side walls? an interesting question. and a complex formula I suppose , for whichever square inch of side wall you happen to point out. Each one in height would vary.
we learned in tech school that at depth, the water is indeed .433 psi for each foot of height (head) 6 feet times is 2.59 psi alright, that is "per Square Inch.
fluid exerts pressure equally in all directions.
the bottom square foot of the tank floor is 144 square inches, is 144 x 2.59 is 373 pounds per square foot. 144 square inches of the lowest level of the sidewall would have the same pressure applied to it. that'd be a strip of sidewall one inch high and 144 inches length , a strip of sidewall 12 feet of perimeter at its lowest edge. at that depth each square inch of side wall has the same pressure as each square inch of bottom.
Ya, this is all pretty much what Artisan had mentioned in his post although I got one weight per area a slightly different number I think. I thought I just might point out again that the .433 times the height in feet gives the pressure at only one square inch at the bottom of that column of water, but more so to point out that the same pressure is equal sideways also at that same depth.
I was wondering if you could find a used bulk milk tank cooler. Plenty of various sizes available, I know the wall thickness isnt anywhere near 1/4 inch but I have no idea of the internal bracing on one of those.

 

[pat32rf]

Since you are building this yourself, you can use lighter than 1/4" sidewalls (1/8" should be plenty) if you weld angle on the INSIDE of the tank and cross brace it wall to wall. It will take a lot less steel to hold two sides together than to try to keep them straight by reinforcing the outside.
I would think that a 4' piece of 1/4" 2x2angle should do welded on the inside of each wall. You could then crossbrace (tie) these together with regular "bedframe" angle.
Don't forget to add a good thick layer of insulation to the sides and top, unless you want to keep the shed at 80degF...

 

[vpd66]

I have a 500 gallon water stove to heat 2400 square feet. Here in NC on the coldest days (in the teens) I have to fire it twice a day and more when the wind blows. 1500 gallons in Wisconsin sounds right as an addition to a wood fired boiler. I have thought of adding a 500 gallon storage tank to minimize the number of times I have to fire my stove. There is a company in Mount Airy, NC that builds water stoves which are essentially storage tanks with a firebox and flues built in. It is not a pressure system as it can't be fired above 212 degrees or it will boil over.

A call to Hick's Water stoves in Mt Airy might be helpful. They do build larger water stoves 1000 gallons and bigger. I am sure they are on the internet.

I'm also hoping that with 1500 gallons of hot water I'll be able to go out of town for a weekend and not have to have someone come over everyday and feed the stove some wood.