# Homemade storage tank design (plywood)



## mikefrommaine (Dec 21, 2011)

I have been playing around with ideas for a plywood tank. I would like to make a tank that fits in a storage area that I have. I have roughly 6.5' by 8.5' to work with. I'm a carpenter so plywood and framing lumber are my materials of choice. Here is a quick sketchup drawing of what I am considering for the tank structure. Based loosely on the BIS storage tank design.

As drawn I have 2x6 and 2x4 side supports overlapping at the corners. There would be sleepers on the bottom bolted to the bottom and top side supports to prevent it from spreading in one direction. Plywood screwed to the sleepers would prevent spreading in the other direction (top and bottom).

The tank would be lined with plywood, rigid foam and a liner (epdm or pvc) Everything would be glued and screwed or bolted.

The short upright 2x6 spacers would be to support the frame work until the plywood is installed.


Ideally I would like to have a tank depth of 5' -- not sure if this design is capable of that? Thoughts? Critiques?

Thanks in advance.


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## DaveBP (Dec 21, 2011)

If you are a carpenter, ask yourself "Would I pour concrete into it?"

Concrete is heavier than water but concrete forms only need to hold for a couple hours. And concrete is not hot. Long term strength requires a bigger safety margin.

Anyway, that's the question that always pops into my mind when a see a lumber frame tank.

If you know any concrete workers ask their opinion.


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## maple1 (Dec 21, 2011)

Could you just frame the corners something the same as a stud wall? Just has a 'wobbly' look to it.

Also, you could also maybe brace around the outside of the box with some metal rods running horizontally?


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## hobbyheater (Dec 21, 2011)

mikefrommaine said:
			
		

> I have been playing around with ideas for a plywood tank. I would like to make a tank that fits in a storage area that I have. I have roughly 6.5' by 8.5' to work with.
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 These are the instruction for constructing your own tank these came with our boiler.  Two things that I would do different.  For your planned height of 5',  keep the 6" spacing until you are within 36" inches of the top, and for your planned width of 6' 5", follow the framing pattern for the sides on the ends also.
There are another 4 pages for this tank building project.  If they would be useful to you, I would be more than happy to send them :exclaim:


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## mikefrommaine (Dec 21, 2011)

hobbyheater said:
			
		

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Allan those plans are great! Just what I was looking for. I would appreciate (and bet others would too)  if you posted the other pages.

Did you use these plans for your tank?


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## flyingcow (Dec 21, 2011)

Tom of Maine would have some good pints to help out. He can make you a liner too. But you probably already knew that.


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## hobbyheater (Dec 21, 2011)

mikefrommaine said:
			
		

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## tom in maine (Dec 22, 2011)

I would suggest that anyone who is considering building a tank out of wood use pressure treated wood and stainless steel fasteners.
I have had to replace old Jetstream tanks like hobbyheater sent along where moisture (not necessarily from the tank) has caused a tank to fall apart due to hidden rot.

It is prudent to put the foam on the inside to cushion the liner. 
EPDM, well, there are enough threads about that elsewhere on this site.


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## Onfoot (Dec 22, 2011)

There is a helpful description of a DIY plywood heat storage tank at: http://www.builditsolar.com/Projects/SpaceHeating/SolarShed/Tank/Construction.htm.

Another fellow describes (with pics) a 900 gallon plywood heat storage tank which he built using Sani-Tred's "Permaflex" product as a paint-on liner.  You can check it out here: http://www.builditsolar.com/Projects/SpaceHeating/PermaFlexTank/PermaFlexTank.htm.

I have spoken with the Sani-Tred folks and they have detailed instructions for applying their products to make a plywood water tank.  And of course Tom in Maine makes custom liners that are probably less trouble to use.

Barrett


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## tom in maine (Dec 22, 2011)

The Sani Tred sounds interesting, but I am nervous about their claims. The reason for my concern is that they talk about a very  thin film layer.
I think it was about 14 mils if I recall correctly.
Thin plastic films tend to be permeable to water, especially water that is hot.

If I was trying Sani Tred, I would definitely be using PT lumber. 

Using a brush on liner for a solar tank with intermittent high temps is different than a constant high temp every evening during the heating season.

It might be worth a try, but most other liners that are applied on surfaces use much greater thicknesses.
I would love to see it work, but have not been able to get over these issues.


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## Onfoot (Dec 22, 2011)

Appreciate your concerns, Tom.  In the way of information, if one follows the instructions that Sani-Tred sent to me, the outcome is "a permanent, impervious, waterproof membrane" that is 40 mil. thick.  They also point to their warranty, declaring that "all Sani-Tred products are life time warranted, permanently flexible, will never bubble, chip, peel, crack, or delaminate. All product literature, product prices, life time warranty, tech data, MSDS, etcâ€¦ is located with our website www.sanitred.com."  But of course they are selling the product!


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## tom in maine (Dec 22, 2011)

40 mils is nice. I think Sani Tred produces 6 mils per coat. That's about 6-7 coats. 
Keep us posted if you try it.

We figure about a dollar a gallon for liners. That is for a double lined tank that equals 40 mils. (as a comparison).


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## mikefrommaine (Dec 22, 2011)

Here is another sketch of the tank structure. Using all 2x6 construction. Instead of spacer blocks I made the side frames 'ladder' construction -- to ease assembly.

Pressure treated sounds like cheap insurance, though not sure if PT has the same bending strength as spf framing lumber. Instead of stainless steel fasteners I would think modern ceramic coated fasteners would hold up?

I've read a fair bit on people who have built aquariums out of plywood. A product called pond armor is popular, sounds similar to sanitread. Quite a few people have trouble with leaks at the seams. I would think the tank would have to be very rigid to avoid trouble at the seams.


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## huffdawg (Dec 22, 2011)

[del][quote author="mikefrommaine" date="1324584612"]Here is another sketch of the tank structure. Using all 2x6 construction. Instead of spacer blocks I made the del]


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## tom in maine (Dec 22, 2011)

The cross pieces on the top are not doing anything structural and they will interfere with sealing the cover.


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## Hydronics (Dec 22, 2011)

mikefrommaine said:
			
		

> Here is another sketch of the tank structure. Using all 2x6 construction. Instead of spacer blocks I made the side frames 'ladder' construction -- to ease assembly.
> 
> Pressure treated sounds like cheap insurance, though not sure if PT has the same bending strength as spf framing lumber. Instead of stainless steel fasteners I would think modern ceramic coated fasteners would hold up?
> 
> I've read a fair bit on people who have built aquariums out of plywood. A product called pond armor is popular, sounds similar to sanitread. Quite a few people have trouble with leaks at the seams. I would think the tank would have to be very rigid to avoid trouble at the seams.



Pressure treated dimensional lumber is made from southern yellow pine which has a greater bending strength than SPF (Spruce-Pine-Fir). Southern Yellow Pine has properties similar to Douglas Fir. In summary: if you've designed for SPF, Yellow Pine will more than do the job.

Mike, In my opinion stainless fasteners are also worthwhile considering the mess and pile of scrap that could result from corroded carbon steel fasteners. I'd heed Tom's warnings as he's speaking from years of experience.


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## mikefrommaine (Dec 22, 2011)

Hydronics said:
			
		

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I was thinking of something like timberlok or headloks. Though they are not that much cheaper than stainless bolts.


http://www.fastenmaster.com/tl_files/fastenmaster/download/ACQ-approval-documentation.pdf

http://www.fastenmaster.com/details/product/headlok-heavy-duty-flathead-fastener.html


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## Rory (Dec 23, 2011)

I'm on my 4th season with a DIY wooden tank.  I used the concrete floor and wall for two surfaces, a wooden interior wall for another, and only ran one outside corner post.  I used 2x6s horizontally as bands, tied at the one outside corner.  I have 2 2" layers of foil faced foam everywhere, and the landscape pool lining material.  The remaining 2 sides and the top are built from plywood.  I didn't seal the top, and have a removable section of the lid on a pulley system.  I occasionally hoist the lid and top off due to evaporation losses.  It's never budged.

Oh yeah, I also lagged the floor bands into the concrete, and I have a double 2x6 with spacers post at the midpoint of the long outer surface.


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## ewdudley (Dec 23, 2011)

Built a 600 gallon decagonal plywood tank during a blizzard once to store milk rather than pour it down the drain.  

Used 2Xwhatever vertical spacers on the outside down the middle of each chord.   Went round and round the outside with 14.5 gauge malleable iron wire -- which we happened to have a couple spools of -- and tightened by winding adjacent strands together.  Lined it with 4mil, and it held up fine until the rotary plow came through.  Took a couple hours.

Dunno if custom liner could be made for a roughly cylindrical tank, but using tension to hold things together is a nice way to go if the circumstances allow. 

Baling wire, what can't it do?


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