Home-made Tankage, Illustrated

[cguida]

Below is an attempt to show in pictures the constuction of a 1000-gallon unpreassureized storage tank.

This tank is made with Fiber-Reinforced Plastic panals, IsoPollySomething-or-Other Insulation boards, and EPDM pond liner. Cost (ex heat exchanger, circ's and plumbing) was about 600 dollars.

Tank shell consistes of 3 8x4 ft FRP panals, riveted with 4 inch overlaps. Makes about a 7 foot diameter cylinder, 4 feet high.
FRP panals cost 40 bucks apiece -- 120 total

Insulation consists of 14 4x8 sheets of IsoPolly????, foil on both sides. Insulation goes inside the shell.
20 bucks a sheet -- 280 total.

Pond Liner -- 25x25(?) tank liner; 10x10 lid membrane
165 bucks

Total so far 565

Other items -- 35 +-
Rivets (I probably used more than necessary)
Copper lid support
Plastic condit threaded nipples (7 -- 4 for lid support; 2 for input and output pipes; 1 for lid vent)

How do you get rigid 4x8 sheets of IsoPolly??? to conform to the curve of the cylinder? I could not figure this out till the trick was explained to me. (Carefully) slice throught the board down through everything except the last foil facing. Do this about every 4 or 5 inches. (Turns out the sheets have some kind of manufacturing line every 5 inches that you can use as a guide). When you are done, you will see that the formerly rigid 4x8 sheet will now conform to just about any curve, something like an old-time roll-top desk.

The tank has 2 layers (2 inches) of insulation all around, and top and bottom. Wish I could remember what the R value is...

Another question is how you get a 25 ft square sheet of pond liner to conform to a cylinder. Answer is to make diagonal plaits in the fabric so it sits right in the tank.

How do you support the lid? I don't have a good picture for this, but the lid support consists of an X of 3/4 inch copper pipe across the top of the tank, with a vertical leg near the center to provide support.

Now we will see if I can actually attach selected pictures to this post. You can see more pictures at (broken link removed) Look for the 'Think Tank' album.

(additional pics coming shortly...)

 

[cguida]

Pictures are not showing up in order...

But here are some more:

 

[cguida]

Lid Support and Flat Plate Heat Exchanger Plumbing

 

[cguida]

Lid and Vent Cap

I started this project in March, and only just finished it. I've never built anything like this before, but I can see now where a handy person could make one of these things in a day or two. It's a cost-effective addition to just about any hydronic set-up.

 

[atlarge54]

Looks like a nice job. If that was my tank I'd definitely have plenty of steel or nylon banding on the outside diameter to share the load on the rivets.

 

[cguida]

My father in law said the same thing, so I got 2 towing slings to strap the tank with, and took this picture just to re-assure him -- especially with the Bungee chord.

Nobody believed the tank would hold water. I was not 100% sure myself. But in actual fact, I snugged the slings up tight with rope, and watched for afew days. No sign what-so-ever of strain. So after a few days, I took the slings off the tank (and used them to pull my truck out of the mud.)

The secret seems to be that water 'wants' to be round, with force spreading out evenly in all directtions. The insulation inside also helps spread the load, I think.

One could try a table-top experiment with paper and a plastic bag -- make a rectilinear paper box and line with the plastic bag. Fill with water. Now do the same thing with a cylinder. See how much water can be contained before you have a mess on your hands. (I haven't actually tried this, but maybe I will someday.)

Anyway, to date the tank is still holding water.

 

[EricV]

Looks great

Where did you get the FRP panels?

Eric

 

[cguida]

I got the FRP panals from a building supply store. Various trade names, e.g. Tuff Coat. They use them to make washable walls in milking parlors, (or in our area) shell fish processing plants. Very tough material; and maybe easier to work with than sheet metal. Drill rivet holes alittle on the large side to alow (?) for thermal expansion -- so says the web literature. In actual fact, the tank can be 180 degrees, but you would never know it by feeling the outside shell. Two inches of insulation seems to work well.

 

[Tarmsolo60]

Nice job on the tank. Similar to my ssts tank but you saved a bunch of $, I wish I had built my own and saved as much as you.

one thing I find useful on my tank is they drilled 3 3"ish holes in a vertical line(top middle bottom) from the outside in through the foam before the liner was installed so a sensor or aquastat bulb can be placed between the outside of the liner and the foam.

I'm jealous of all the money you saved!

 

[pbvermont]

smee,
you done a good thing. I love it: "water wants to be round!"
"Water, water everywhere", ...and you put it in a 'play-pen!
I want to be 'round THAT: --SAVIN' MONEY! YOU DA MAN!
You oughta form a "think tank." (while you're at it).

 

[Hydronics]

Great job Smee. Are you going to add a seperate coil for domestic hot water or take it off the exchanger? What are you running for high & low temps in the tank & how often do you fire the boiler.

F.Y.I.: a cylinder is an ideal shape for a tank because the entire wall is in tension (hydrostatic force is attempting to pull it apart). A rectangle on the other hand induces a bending moment (like a beam) along the straight length of each side. A member must be much larger to support a comparable moment than to support tension.
Using your paper example: squeeze the sheet on each end between your fingers and try to pull it apart (tension), now lay the sheet on two supports (one at each end) you don't have to apply a force in the middle (bending moment), it's bending under it's own weight.

 

[Tree farmer]

Smee,
you inspire me to actually start thinking about investing and building a tank, almost. Maybe when I finish other open ended projects in the house. That tank looks awesome but the price points even better!

 

[Bad Wolf]

Egads!!
Hydronics, You sound like one of those En-ga-neer types!!

You probably have "the knack"

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(if it maks you feel better I'm a Mech/Materials engineer)

 

[Hydronics]

Greg,
You nailed it - a P.E. to make it worse! I'm Civil/Structural.
Didn't you say you're in Colchester? I sent you the names/number for truck length wood in a p.m.
If you don't mind, I'd like to check out & discuss the storage system you made sometime. I'm in Willington.

 

[Bad Wolf]

Haven't seen anything in th PM yet.

You know the differance between a Mechanical Engineer and a Civil Engineer?

A ME builds weapons systems

A CE builds targets

 

[Chad Robinson]

cguida, if you're still around, do you still have this tank? If so, what temps have you exposed it to and how is it holding up? I'm going through the storage-tank-style debate everybody hits, and this seems like an elegant solution.