Started Tank Construction Today

[WoodNotOil]

I started constructing my heat storage tank today. I have also created a web site to house images, design information, and to document progress. Much of the site is still under construction, but I am adding to it daily. Feedback and suggestions are welcome. Link to the site is in my signature.

 

[Willman]

Link to the site is in my signature

Nice start. Keep the pics coming.

Will

 

[Grapenut]

What material are you using for insulation? Also, what are you constructing the top from? Nice start on the site and the tank.

Thanks!

 

[WoodNotOil]

I plan to use approx. 3" polyiso insulation that comes in 4x8 sheets. I have not gone down to the store yet and picked it out. I plan to avoid having a foil layer or at least position any foil to minimize heat transfer. I have only bought blocks and mortar so far. If anyone has suggestions for other parts of the project, I can still alter a few things.

I have not come up with the complete lid design yet, but I have a few thoughts about it. The first layer will be EPDM with plyiso insulation just behind that. I may also use some rigid foam insulation after the polyiso for stability. There may even be plywood and other wood involved to make it strong enough to put things on. If anyone has designed a good lid, I would love some details.

 

[sparke]

The lid is the worst part of my project. I originally siliconed the polypropylene lid to the top. The problem is nothing adheres to polyprop. well. Also where you fold the liner to get it in the tank becomes an issue. It makes bumps and un-evenness etc... My solution and it is working well so far. I cut 2" foiled polyiso. board to a tight fit inside the top of the tank. I then used can foam and filled in all the cracks and holes. I also filled the areas where the liner was folded. That is the toughest place to seal. Not sure how the polyiso. will hold up over time but right now I seem to have a very good seal. The key is the foam (Great Stuff brand). You may consider using a waterproofing product and doing away with the liner. The lid would be much easier that way. Keep the pictures coming.

 

[MrEd]

I am considering a similar project, but 2000 gallons. Why does everyone use a liner? why not just make it waterproof with the cement and a pool paint? Does that require a lot of skill to work? Seems to me it makes sense to make it right the first time and not have to worry about replacing a liner down the road.

I have no idea how hard it is to make a watertight tank out of concrete, but I certainly have seen plenty of them. In the islands they make 2000-3000 gallons cisterns all the time to store rain water for drinking.

 

[steam man]

I am considering a similar project, but 2000 gallons. Why does everyone use a liner? why not just make it waterproof with the cement and a pool paint? Does that require a lot of skill to work? Seems to me it makes sense to make it right the first time and not have to worry about replacing a liner down the road.

I have no idea how hard it is to make a watertight tank out of concrete, but I certainly have seen plenty of them. In the islands they make 2000-3000 gallons cisterns all the time to store rain water for drinking.

Most constructed tanks probably have the insulation on the inside walls. I presume if you were going to coat the tank the insulation would be on the outside. If anyone can come up with a foolproof coating for concrete that can expand under elevated temperatures and contract without failing, I'd like to know about it. I've seen a number of Stainlees steel cistern tanks made for collecting rainwater in Puerto Rico that could handle the temperatures. However, they are pricey also.

Mike

 

[free75degrees]

I would be worried that the temperature fluctuations between 60*F and 180*F might causing cracking in the concrete. Maybe this isn't an issue but I'd research it before going this route. In the end I decided on epdm for my tank to be safe.

I am currently thinking about my lid design and will probably start it this weekend. The tops of my side walls have a very slight slant and the epdm lays over the top of the slant. This is so that any water that gets on top of the wall will drip back into the tank. My lid will be covered with epdm on the bottom of it. I am thinking of tacking some pipe insulation around the edges of the lid then stretching the epdm over the pipe insulation. This way when it rests on the top of the walls the pipe insulation will deform slightly to make a good seal. At the corners where the excess epdm from the inside of the tank gets bunched up I was going to make a gap in the lid and allow the lid epdm to stretch over the excess corner epdm. It's hard to describe, and also hard to visualize, so I'll send pics when I get it done.

 

[sparke]

Maybe someone should give this guy a shout and see if his method worked. See pictures about 1/2 down the page. http://picasaweb.google.com/pittman.jim/KevinSBoilerWorks?authkey=apvdOuoreyAdMc9MtlxgAJy5Yk8

 

[free75degrees]

Not sure how the polyiso. will hold up over time but right now I seem to have a very good seal.

I understand that we want a good seal to prevent heat and vapor loss, but don't we also need to allow some air movement in and out to allow for expansion/contraction? I was going to try and make my seal pretty good and any imperfections would allow a small amount of air movement for this purpose.

I also talked to a guy who said he likes the fact that his tank loses vapor in the winter. Around here it can get very dry in the winter and losing vapor means the tank is acting like a warm air humidifier, which is a nice side effect. He piped in an automatic water refill valve to keep it at the right water level.

 

[free75degrees]

i cant remember which but i think that either styrofoam or isofoam ONLY loses 1/2 its r value when it is saturated...good luck

When I said that my seal might not be perfect I meant that I might have air exchange between the air at the top of the tank and the room air. My polyiso will be sealed from water contact.

 

[free75degrees]

good luck with murphy & her law!

haha, I buried Murphy in the tank hole before I poured the slab floor.

 

[sparke]

I was concerned with pressure build up also. I think it is impossible to get the tank perfectly sealed so I am going with your theory, a bit of vapor leakage is OK. If it ever becomes an issue Eric has a good solution. Put in a small piece of pipe with a small rubber ball sitting on top. If the pressure builds up it can escape otherwise the ball will rest on the pipe essentially closing it.

 

[MrEd]

Maybe someone should give this guy a shout and see if his method worked. See pictures about 1/2 down the page. http://picasaweb.google.com/pittman.jim/KevinSBoilerWorks?authkey=apvdOuoreyAdMc9MtlxgAJy5Yk8

Thats exactly the post I was thinking about when I read the thread and made my comments - his seemed liked a pretty slick setup, nicely constructed and waterproof to boot. It would be interesting to know if it performed as expected.