Wood storage tank, w/pics

[Jackpine Savage]

This is my first attempt at pictures, I hope it works. I should also add a disclaimer, I am not an engineer, and I hope this tank holds water in the end. All feedback is welcome.

I was pretty much forced into an unpressurized system. There is no way to get a tank down into our basement, in fact I still haven't gotten the Tarm down there yet. The boiler room is narrow, and I didn't want to give up the space that a round tank requires. So that led me to a plywood tank. I'll be using copper tube HXs, purchased from Bioheat, for boiler input and DHW.

The walls of the tank are basically stud walls, 2x4s 12" on center, fastened to the floor with 1/2" concrete anchors. I used 5/8" plywood to line the tank. Two layers of 1" poly-iso foam line the interior of the tank. I'll add r-13 un-faced fiberglass in between the 'studs'. That should give me a little less than r-26 for the walls. I put 3 layers of foam on the floor for an R-19.5. The interior of the tank ended up being 92"x45"x45" which I calculate at 805 gallons.

Some pics of the pressure treated bottom plate:

 

[Jackpine Savage]

Here are a couple pictures of the walls going up. The floors were not level of course, so it took a lot of tweaking to make everything come together.

 

[Jackpine Savage]

Here is a picture of the fiberglass insulation in the back wall and one with all the walls and plywood in place. There is an additional 2x4 in the corner that is screwed to the end 2x4 in each wall to tie the corner together. I have all the foam in place now as well. My DW has our camera at a dog show this weekend so I'll add some more pics later.

I think I might add some straps around the corners of the top and bottom plates just as cheap insurance.

I haven't completely thought out the cover yet. I'm thinking of having a 12" ledge that hangs out into the tank to run the piping through. Then have a cover that is hinged to the ledge.

Now to start thinking about the piping.

 

[ken999]

Please excuse my ignorance...what material will actually be holding the water?

 

[Jackpine Savage]

I should have mentioned that, it will have an EPDM liner.

 

[Dave T]

Good to see more creative people speaking up and showing their projects I will recomend you use the straps and personally I would not be shy installing a few extra straps while your at it "cheap insurance" is well said.. I have seen on this site where somebody ran a fake header all the way around the tank on top, then left a gap in the 2x12 fake header and ran his lines through the gap left, and into the tank, then he used silicone to seal around the lines..I don't know if you could find it with a few searches but worth a try..Are you using one solid pice of EPDM or trying to seam it ..Dave

 

[ken999]

Thanks.

Looks like a nice project.

 

[Jackpine Savage]

Thanks too.

It will be a one piece EPDM with folds. It was pond liner from Home Depot.

 

[ken999]

Are you layering the floor foam with anything to ward off compression or will the foam carry the weight ok on it's own?

 

[Jackpine Savage]

That is a good question Ken, it made me do some research. I am planning on just the epdm liner covering the foam. I'm using Firestone ISO-R, it is rated to 20 PSI. By my calculations it should be seeing less than 1.7 PSI. I've read about others using the same approach but sure would like to hear if anyone has run into problems.

 

[88rxn/a]

is that spray insulation? if so what did you use?

 

[ken999]

Sounds good!...I'll be keeping an eye on this thread.

 

[Jackpine Savage]

The poly-iso foam is foamboard.

Here are the latest pics. One showing the 2x4 in the corner. I'll add a 1/2 inch plywood filler and another 2x4 to get out to the corner. I think that I will skin the outside with 1/2" plywood. There will be a couple tension straps across the top.

I think I'm also going to put the aluminum layer to the inside on the inside foam boards, and then run foil tape in all the corners as a second layer of waterproofing. In one corner I'll put a plastic tube through to the outside so I can tell right away if the liner starts leaking.

 

[Jackpine Savage]

I hope if anyone sees any glaring errors they will chime in.

Here is a pic of the coils going in temporarily so I can start the piping. I'm waiting to put the liner in after the piping is done. The coils came with three small rubber feet zip tied to the bottom coil. Will that be enough to protect the liner? I've read of setting the coils on epdm wrapped concrete block, and making a CPVC cradle. I'd be interested in hearing recent experience of what works or doesn't.

 

[Jackpine Savage]

Finally made more progress on the tank today. I added a few reinforcement straps, insulation, and plywood. There's also a picture of the liner leak early warning system. And a picture of the DW anxiously awaiting more heat for the house.

I have the lid designed. I picked up a bunch of plumbing supplies last night, so thats next.

 

[Jackpine Savage]

The rest of the pics ....

Someone let me know if I'm wasting bandwidth.

 

[DaveBP]

Before I ran into a couple propane tanks that I can wheel right into my basement I was thinking about doing just about what you've got in the pictures. Did you use construction adhesive to fasten the bottom plates to the plywood 'subfloor'? That's my answer to "how many nails should I put in this assembly".

If the long wall is a 4' x 8' sheet of plywood, you'll have well over 2 tons of force pushing it away from the basement wall; most of that toward the bottom. I was planning to bolt down a rugged steel angle to the concrete floor along the outside of the walls to keep it from buckling away. I have a 5x5 x3/8 x 26 feet long that I'm trying to find a use for.

A few years ago I was over to a friend's house whose garage roof was obviously failing from accumulated heavy snow load. We were trying to decide if it was safe to go in and get his tools out (we were very reluctant, you could 'hear' those rafters whining) when it just let go and came down. Wood bends just so far and then it explodes/fails. I get the creeps just remembering that sound.

Looks like good careful work. Run a straight line string across the top corners as you fill it to monitor the bending as it comes into its load. 1/4" bend in 8' would be about the 1/360 bend that very conservative floor joist loads are kept to. 1/240 is considered safe if you have good quality lumber. The 12' 2x10's in my barn hay loft have almost 1" bend to them when the loft is full.

Keep us posted. Good pics.

 

[Der Fuirmeister]

What's the tempurature rating of the EPDM liner?

What do you have supporting the coils (preventing holes in the liner)?

Please let us all know how it works when you fill it up, and again when it's heated.

 

[Der Fuirmeister]

Are you layering the floor foam with anything to ward off compression or will the foam carry the weight ok on it's own?

FYI for those considering the foam. Dow has the compression ratings on their web site specs. What we see in lumber yards around here is typically 15 psi They also have 25psi. The polyisocyanurate is 25psi.

link to DOW spec....

http://building.dow.com/na/en/products/insulation/thermaxmetal.htm

 

[DaveBP]

Are you layering the floor foam with anything to ward off compression or will the foam carry the weight ok on it’s own?

I think any of the rigid foams can take the compression of the weight of a tank spread out over the whole bottom surface. My concern is the long term temperature limit differences between polyisocyanurate and polystyrene. Styrene's published service limits that I've seen hover around 160F. Cyanurates usually have higher limits closer to 190. You see a lot of different specs but that seems to me to be the averages.

 

[Fred61]

Did you purchase your copper coils all assembled or did you build them? If you purchased them, Do you mind sharing your source and approximate cost?

 

[Der Fuirmeister]

Are you layering the floor foam with anything to ward off compression or will the foam carry the weight ok on it’s own?

I think any of the rigid foams can take the compression of the weight of a tank spread out over the whole bottom surface. My concern is the long term temperature limit differences between polyisocyanurate and polystyrene. Styrene's published service limits that I've seen hover around 160F. Cyanurates usually have higher limits closer to 190. You see a lot of different specs but that seems to me to be the averages.

Good point. The Dow site lists max temp at 250F, and......is flammable.

We use Rockwool type insulation for high temp applications around engine exhausts etc. It's 1200 degree rated working temp. and they have cloth, preformed shapes for pipe etc., and flat sheet. R values similar to styrene. Compressive strength is less but this type of product would be much better in areas exposed to heat.

 

[Jackpine Savage]

I wish that I had glued down the bottom plate to the concrete, but too late for that now. I think I will add a section of angle iron in the middle of the 8' section. I like the idea of setting up a couple of strings to check for deflection.

I bought the copper coils from Tarm almost two years ago. Yep, I've had the boiler sitting in the shed that long too. Time flies.

The coils came with three small rubber pads zip tied to the bottom coil. I'd be interested to hear if anyone has used them or came up with something better.

It sounds like you want to keep the EPDM under 175 degrees.

I ran across plans for another wood tank for folks that want to watch their tank charge. I wonder if you can see stratification .

http://www.jonolavsakvarium.com/eng_diy/2200litre/2200litres.html

 

[DaveBP]

Now that is an aquarium! Or a lap pool for someone that really just wanted to practice turns.

First thing I noticed was the thwart across the top, like a canoe. Great idea, even if it was just a cable attached to brackets.

 

[Jackpine Savage]

I'm still making progress, albeit slow. I had to start working on the piping before I could work on the lid and the liner. Here is the start of the lid. There is an outside frame of 2x4s, with some cross 2x4s for the strap hinges to screw into. The interior was filled with foam board, 3 1/2". The top is 1/4 plywood.