Building a water tank

[vpd66]

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.

I've looked at quite a few milk bulk tanks and one would work, but all of them are made of stainless steel which even at scrap price makes them expensive.

 

[vpd66]

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...

Hey! thats a great idea. I never thought about that. You are right, it would take alot less steel because the tie crossbraces would have extention load on them. I could weld 2 angles vertically evenly spaced across the 7ft length then tie them togeather across the 5ft width. This also does not take much away from the capacity of the tank. Great idea!!

 

[jenkinsph]

While the internal bracing can be more efficient and has its advantages it also increases the surface area prone to rusting. If your tank is clean and smooth inside it will be alot easier to clean and repaint.

 

[powerpace]

Even on most 1500 gallon fire tankers they use only 1/8 steel. It is baffled on the inside to prevent sloshing. The baffles also help with tank integrity during stress. Baffles are about two feet apart and crossed.

 

[vpd66]

While the internal bracing can be more efficient and has its advantages it also increases the surface area prone to rusting. If your tank is clean and smooth inside it will be alot easier to clean and repaint.

Water quality will be checked and adjusted annually. I also have sourced an epoxy paint that is good up to 250 degrees that I'm thinking of using on the inside.

 

[Den1952]

to mention once more about the milk tank, around wisconsin anyway there are lots of them around. Usually found in a shed or behind a building somewhere. Lots of folks had picked up old used ones years ago and would use them for keeping the daily catch of fish. To get one from a private party, some old timer who no longer fishes, might be a totally different price involved.

 

[vpd66]

to mention once more about the milk tank, around wisconsin anyway there are lots of them around. Usually found in a shed or behind a building somewhere. Lots of folks had picked up old used ones years ago and would use them for keeping the daily catch of fish. To get one from a private party, some old timer who no longer fishes, might be a totally different price involved.

I'll have to look around.

 

[jenkinsph]

Water quality will be checked and adjusted annually. I also have sourced an epoxy paint that is good up to 250 degrees that I'm thinking of using on the inside.

I am a plumbing and heating contractor, thats what the "ph" on the end of my user handle stands for. I am only pointing out what I have found to be issues over a long career working with hydronic heating systems. Most hydronic heat systems are pressurized and closed systems which greatly reduces air entrainment and as a result less corrosion. I can easily see your reasons for opting for an open air system for your storage needs. At the same time I have spent alot of time chipping away rust. I can only advise you to carefully consider the maintenance problems with an open system. Using the proper corrosion inhibitors and/or anti freeze solutions should also help.

 

[Gary Fowler]

I have seen similar sized tanks built with only an x brace of 1.5 x1.5 angle on each side. You would need to first build an angle box frame on the bottom and top and all 4 corners. Seal weld the tank to the angle which will be easier than trying to seal the edges. Then add the external X brace. It needs to be skip welded to the steel shell at least 3" on 12" centers with alternating the skip on each side of the angle. I dont think you would then need any internal bracing. I wouldnt use anything thicker than 1/8" as long as you put a good internal and extenal coating on it to prevent corrosion. Go thicker if external or internal corrosion will be an issue.

 

[brokenknee]

I have heard on hearth.com of people using old propane tanks. They usually purchase the 500 gallon ones and put two or three together. There is a lot of information on that site about boilers and adding storage.

I admit I did not read all the treads, so if this has been suggested before sorry.