2000 gal plywood sump
- Thread starter karimwassef
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karimwassef
Active member
You mean a fresh water or other coolant loop in the concrete?
Could even use copper since it's encased in concrete and epoxy I guess..
I need to think about this. I didn't consider the thermal benefits or penalties of the slab's direct contact... good point.
Could even use copper since it's encased in concrete and epoxy I guess..
I need to think about this. I didn't consider the thermal benefits or penalties of the slab's direct contact... good point.
karimwassef
Active member
Thinking it through... the large surface allows me to use a large PEX tubing to cool or heat. I think embedding it in the concrete may be an unnecessary complication and maintenance risk? The exception would be using copper lines for a freon loop (compressor, external radiator and fan) to really cool the concrete. But still- expansion/contraction... feels so risky
I do plan on having gas so running hot water would make for a very efficienct heating loop.
Intrinsically though, the current design should keep the slab very cool... the back room is shaded constantly. The sunroom has a false wooden floor that would keep the slab there shaded as well. So with limited radiated energy and being intimately heatsunk to the shaded earth below, it should help "normalize" the temperature... cooler in the summer, warmer in the winter?
The large underground cooling loops will do this even more being at 10' deep. The air loop will cool the air & the saltwater loop will cool the water. The heat exchangers are the buried pipes directly.. no secondary heat exchangers.
I do plan on having gas so running hot water would make for a very efficienct heating loop.
Intrinsically though, the current design should keep the slab very cool... the back room is shaded constantly. The sunroom has a false wooden floor that would keep the slab there shaded as well. So with limited radiated energy and being intimately heatsunk to the shaded earth below, it should help "normalize" the temperature... cooler in the summer, warmer in the winter?
The large underground cooling loops will do this even more being at 10' deep. The air loop will cool the air & the saltwater loop will cool the water. The heat exchangers are the buried pipes directly.. no secondary heat exchangers.
der_wille_zur_macht
Team RC
Having the concrete floor as part of the structure and waterproofing of the tank scares me a bit, honestly. It's putting all your eggs in one basket. You basically have no room for issues, there is a single point of failure. If it were me, I'd go with the all-wood construction and just let it sit on the concrete. At the very least, this will allow for any flex or expansion in the wood/epoxy that might be at different rates than the concrete. You're talking about a very large tank - dynamics that don't matter in typically sized tanks are going to be multiplied.
karimwassef
Active member
True, but it's 18" of concrete with three layers of rebar coated in drylock.
It's basically as watertight as a pool... so not worried about the concrete cracking.
The wood-concrete interface.... that could exhibit different expansion/contraction or at least fatigue the joints over time. But the interface is epoxy so very hard. The weakest link would break first - epoxy or wood?
There are also two kinds of wood. Plywood inside and 2x12 outside. The 2x12s should be very strong in tension. I would expect the plywood to be strong in tension and compression.
Hard to call.
Would the sidewalls made on concrete block be less prone to failure since the expansion coeff should be the same?
It's basically as watertight as a pool... so not worried about the concrete cracking.
The wood-concrete interface.... that could exhibit different expansion/contraction or at least fatigue the joints over time. But the interface is epoxy so very hard. The weakest link would break first - epoxy or wood?
There are also two kinds of wood. Plywood inside and 2x12 outside. The 2x12s should be very strong in tension. I would expect the plywood to be strong in tension and compression.
Hard to call.
Would the sidewalls made on concrete block be less prone to failure since the expansion coeff should be the same?
karimwassef
Active member
Is there a precedence like this problem? Don't we use wood studs and beams over concrete floors? Is there relief built in?
der_wille_zur_macht
Team RC
Yes but if the wood shifts a millimeter on the concrete, there aren't thousands of gallons at stake.
When I disassembled my 360g, the weakest link was epoxy bonding to already cured epoxy, even when proper surface prep had happened. It was still strong but that was clearly the weakest part of the entire structure. Your plan revolves around that type of bond in the most critical joint, and it's between dissimilar materials and under changing pressure from all your surges etc. Hence my reservations!
karimwassef
Active member
Way to strike FUD - fear, uncertainty and doubt
I guess if I want to take advantage of the cool slab without the hassle of forms or rebar, the only remaining option is to use a 3 layer high concrete block wall ~ 24"
I guess if I want to take advantage of the cool slab without the hassle of forms or rebar, the only remaining option is to use a 3 layer high concrete block wall ~ 24"
Something to think about. If for some reason the wood failed it would likely result in a total blowout. For example the epoxy developed a crack/hole allowing water into the wood causing rot. You might not notice until it's too late due to the epoxy coating hiding it. The epoxy might be tough but your talking about walking, setting up ladders & working in there over a period of years. Now if you went with poured concrete and it started to fail you would be much more likely to notice a crack giving you time to fix the issue before total failure. Think of it as a small swimming pool, would you rather have one made of concrete or plywood? It might not cost as much as you think especially if your having the room built at the same time. Even if it does take longer and cost a bit more, why would you go cheap on the most important part of the entire system? Your ideas/plan might turn out great & likely will. Personally I'd be waking up with nightmares playing through my head, but that's just my own paranoia & I tend to WAY overbuild everything.
Good luck with the build & I can't wait to see what you have in store for the finished system.
Good luck with the build & I can't wait to see what you have in store for the finished system.
der_wille_zur_macht
Team RC
Wood is very forgiving in terms of noticing and solving problems. It tends to fail very slowly. If the wood core gets wet and starts to delaminate, you will get a slowly developing bow in most cases. I've seen wood tanks that had run partially failed for months. I had a local guy who had a tank with a bad leak that damaged the wood and ended up bowing several inches. He fixed the leak and kept running it with the bow. I wouldn't have but there was no catastrophic failure. My own tank had a pinhole underwater allowing water into the eurobrace for months. I lowered the water level an inch so the pinhole was above the water line and kept running it, even with the damaged wood core. A year or so later I drained the tank and ran fiberglass over the damage. The tank ran for several years after that.
I can't speak to personal experience with concrete but I can say wood tanks are very forgiving.
I can't speak to personal experience with concrete but I can say wood tanks are very forgiving.
karimwassef
Active member
Actually- I think wood is "self-healing" as it rots.... basically, the water that causes it to swell can actually create a seal stopping additional leakage.
It's bizzare but I've seen it in my test builds. Over time, the swollen wood weakens and will eventually fail, but imagine a glass that self seals for reference!
Also, the wood is actually sealed before being glued to the concrete so the failure would be an epoxy-epoxy failure. The wood-epoxy bond is insanely strong... stronger even than the wood alone or epoxy alone. The wood fibers "drink up" the epoxy creating a new matrix composite medium (assuming proper surface treatment).
Concrete-epoxy is also very strong. The concrete is porous.
I don't know about concrete-drylok-epoxy. I may choose to eliminate the sealant to avoid introducing weaknesses.
It's bizzare but I've seen it in my test builds. Over time, the swollen wood weakens and will eventually fail, but imagine a glass that self seals for reference!
Also, the wood is actually sealed before being glued to the concrete so the failure would be an epoxy-epoxy failure. The wood-epoxy bond is insanely strong... stronger even than the wood alone or epoxy alone. The wood fibers "drink up" the epoxy creating a new matrix composite medium (assuming proper surface treatment).
Concrete-epoxy is also very strong. The concrete is porous.
I don't know about concrete-drylok-epoxy. I may choose to eliminate the sealant to avoid introducing weaknesses.
der_wille_zur_macht
Team RC
Some day I would like to build a tank with foam cores instead of wood. Fiberglass in the epoxy. It would be strong, light, inherently waterproof, totally inert and stable, and it would last forever. Either plain insulation foam (blue or pink) or foam honeycomb.
karimwassef
Active member
With epoxy inside and out?
der_wille_zur_macht
Team RC
Epoxy with heavy glass cloth.
karimwassef
Active member
Ok. So it's basically using the foam as a form for a fiberglass tank.
As long as the foam was fully encased, it should be comparable to the plastic tanks. At this scale though, they all use ribs or ridges to increase strength so you'll probably have to engineer that in.
Fiberglass isn't cheap either - so I'll go with wood or blocks.
I'm really intrigued by the potential for the slab to passively cool the water. That's probably why I'm pausing on just going with the plywood floor.
As long as the foam was fully encased, it should be comparable to the plastic tanks. At this scale though, they all use ribs or ridges to increase strength so you'll probably have to engineer that in.
Fiberglass isn't cheap either - so I'll go with wood or blocks.
I'm really intrigued by the potential for the slab to passively cool the water. That's probably why I'm pausing on just going with the plywood floor.
der_wille_zur_macht
Team RC
The strength comes from the thickness of the foam - at 2" thick you're getting an incredible advantage versus a 3/4" thick wood tank or a ribbed frp tank or just a thin fiberglass tank. Any tank wall has tension on the ouside and compression on the inside - with a thicker wall core, you're basically giving leverage to the fibers under tension. If you leave the inside and outside skins alone and just double the wall thickness, the stiffness goes through the roof. You could get even more strength with careful cloth selection. In the end this approach wouldn't make much practical or financial sense compared to a wood tank, but it would be a super fun engineering project.
With regards to passive cooling - why not just put a ground source loop in under the concrete and circulate the water through a heat exchanger? Then you're taking the concrete out of the picture - after all, ultimately, the cooling effect is coming from the earth under the slab, not from the slab itself. Could just use a coil in the air to cool the room, wouldn't have to be in the water. With that much water and that much surface area, you wouldn't really need to cool the water directly. If you concentrated on keeping the entire room at the right temp, the water would be there naturally.
With regards to passive cooling - why not just put a ground source loop in under the concrete and circulate the water through a heat exchanger? Then you're taking the concrete out of the picture - after all, ultimately, the cooling effect is coming from the earth under the slab, not from the slab itself. Could just use a coil in the air to cool the room, wouldn't have to be in the water. With that much water and that much surface area, you wouldn't really need to cool the water directly. If you concentrated on keeping the entire room at the right temp, the water would be there naturally.
karimwassef
Active member
I have plenty of alternative cooling mechanisms in the design:
1. Geothermal air cooling loop (10' deep )
2. Geothermal saltwater cooling loop (also 10')
3. Chiller
4. Evaporator tower
5. Blower fan over the 13' length of the sump
I was looking for a freebie, especially a passive freebie.
I'm going back to all wood. In case I want to make drastic changes, this would be easiest to change.
You can see my cooling loops in the first few minutes of my build video
1. Geothermal air cooling loop (10' deep )
2. Geothermal saltwater cooling loop (also 10')
3. Chiller
4. Evaporator tower
5. Blower fan over the 13' length of the sump
I was looking for a freebie, especially a passive freebie.
I'm going back to all wood. In case I want to make drastic changes, this would be easiest to change.
You can see my cooling loops in the first few minutes of my build video
karimwassef
Active member
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der_wille_zur_macht
Team RC
OK you've got cooling covered!
I would probably end up with wood as well. It's forgiving, cheap, relatively easy to DIY, and easy to change later. Do it right and it'll last as long as the concrete IMHO.
I would probably end up with wood as well. It's forgiving, cheap, relatively easy to DIY, and easy to change later. Do it right and it'll last as long as the concrete IMHO.
karimwassef
Active member
Yup.
I started with cooling actually. Solar radiation is 1050 W/m2 ~ 11.3KW/ft2
The sunroom is 25' x 20' so ~ 5.7MW ..... silly kind of numbers
The display tank alone is 9' x 12' ~ 1.2MW
That includes light as well as heat, of course. Still silly big numbers before the greenhouse effect.
I started with cooling actually. Solar radiation is 1050 W/m2 ~ 11.3KW/ft2
The sunroom is 25' x 20' so ~ 5.7MW ..... silly kind of numbers
The display tank alone is 9' x 12' ~ 1.2MW
That includes light as well as heat, of course. Still silly big numbers before the greenhouse effect.
