Adding a septic tank with water for heat Storage????

[Splitz]

I have an almost new 2000 Gallon concrete septic tank behind my shed that I used as a holding tank for two years. I have been trying to think of what to do with it and the idea of thermal storage crossed my mind, but I wasn't sure it was worth it. I thought of insulating it but leaving above ground to avoid water issues. If anyone has any constructive ideas on how this might be accomplished I would love to hear them as I already have the tank and it's too heavy (expensive) to move or sell. This has been an interesting thread, like most people here I hate to be "inside the box" or we would all have modulating propane boilers or be slaves to the oil companies.
(p.s. using the ACTUAL sh*t tank is a little out there!)

 

[maple1]

I don't think I would try one above ground - they are designed to be fully contained (surrounded by dirt) when full. Not saying it would burst, but don't think I'd chance it full of 2000 gallns of hot water.

 

[2.beans]

sorry for the late post. i do know someone that spray foamed a 500 gallon propane tank and put it under his addition on his house. no fixing it or knowing if ground water is affecting it. its been working fine.

 

[Tennman]

Airplane, and all.... Most all of us understood you weren't planning on heating poop as energy storage.... just that some of us just couldn't resist the temptation of going there. Speaking for myself, they just beat me to the obvious jokes. But it was symptomatic of the fact that a discussion of using a septic tank as storage was a novel topic.

Maple1, Yeah my last caveat post stating it's all about the insulation was not to imply I thot the septic tank was a good idea!! I'm a closed system guy with autofill backflow preventers managing pressure and chemicals managing rust. Since I'm around large industrial and government facilities I just think that way. Quite a few posts here about folks happy with non-pressurized systems and lined plywood storage tanks. I'm a closed, pressurized kind of guy.

AND just about the time this thread is running out of steam... Splitz reenergizes it. Splitz, if you lived near me you'd make a tornado shelter out of it.... If you want to use it for storage..... just insulate the CRAP out of it.... sorry just couldn't help myself. I'm going to stop before I talking about how energy always is trying to find a way to get to a LOWER energy state. All our btu's are relentless and untiring in that law of the universe.

Ya'll have a good day... now I gotta make some money.

 

[Splitz]

Yeah, maybe a bomb shelter...or after seeing Steve's post on Happy Greenwood owners, an outdoor boiler shed...hard to burn down concrete!

 

[HeatFarmer]

Imagine the smell coming out of the vent pipe with 180 F poo.

The plus side is you could run your BBQ off-in the fumes.....if you didn't smoke too close to the tank........KaBOOM.

 

[roknwoe]

I have been known to think out side of the "Box" sometimes a little to far.

I was just thinking the other day about putting a HX in my actual septic tank when the boiler temp drops. Have a loop on a aquastat that when the storage gets so cold if a fire hasn't been made to circulate water through the actual septic tank. For obvious reasons I would want a loop going from a heat exchanger in the tank to another one that the boiler water would go through so if is does leak or erode it wont contaminate the boiler water or drain you system into the septic. Septic tanks seem to be nice and toasty between the warn water and other things that go into them plus the bacterial reaction.

:cheese: How far out of the box is that?

You have a very stinky idea! (pun intended). I am jealous I didn't think of it.

Actually, I think this would not work in the long run, because similar to "stealing heat off a hot smoke pipe of a stove to heat your house", it cools the pipe too much and can/does create creosote on the inside of the pipe and perhaps clog it up.

If you cool off the septic tank too much, it might clog up the septic system because heat works with the good bacteria to break down all the nasties inside your septic tank, on its way to the drain field. You might acquire some BTU's for your home at the expense of creating trouble in your septic tank and drain field...which would be very costly to fix.

The bottom line:

--dont mess with mother nature!

 

[senoiaslim]

Ok, been a while for this thread, but here goes. Lets say you insulate the crap out of the tank, put a copper coil in the tank, to make it a closed system going out of the tank to the mix valve and blend it with your hot water heater. You run the water from the septic tank to the wood boiler in an open system. Does anyone think that would be a good idea? Basically I am looking for a system that would be able to shut down without freezing during some times in the winter if we are not at home.

One other thing, how would I figure out the size of the copper coil to have in the tank that would run to the mix valve?

 

[Tennman]

Sooo.... why do you care about keeping the poopy water in the septic tank warm?

Resurrecting this thread from when I was younger may just be the highlight of my day. Well, I've changed since then but the physics hasn't. Thanks for the memories.

 

[tom in maine]

No doubt it will work for a while. I have some customers in the Southwest who have used septic tanks for solar systems.
There is an issue with concrete being affected strength-wise when heated over 140F.
We made liners for those tanks in the SW. Apparently the contractor had issues with cracking as well.

 

[E Yoder]

What I'm wondering about how copper would hold up in a corrosive environment like an "in use" septic tank.
Maybe SS or Pex.

 

[E Yoder]

This thread is priceless.

I actually fed about 50+' of 3/4" Pex into a septic tank once by mistake. Homeowner had buried a 4" PVC conduit from basement to outdoor boiler. We were feeding a 3/4" Pex pipe down the conduit to couple to the insulated pipe to pull it back through... We fed about 50' into the tank til we smelled a whiff.... Tried to pull it back- not happening.... Then the homeowner comes over apologizing for showing us the wrong 4" pvc pipe.... !! Was stubbed up through the slab for a future upstairs bathroom that never happened. The right pipe was behind the drywall.
Had to dig up the tank covers to get the pex out.
Wow, precious memories..... Wish I had a picture.

 

[tom in maine]

What I'm wondering about how copper would hold up in a corrosive environment like an "in use" septic tank.
Maybe SS or Pex.

Wouldn't that be a fun experiment. I have a friend who is a septic expert. Was a mom to 7 kids, went back to college and got her PHD in microbiology, specializing in the biology of septic tanks. She was very casual about working in tanks, testing the fun stuff in them.

I would not consider using PEX in a tank with any fittings. Would use AL/Pex or stainless. And no fittings inside. There is a risk of contamination sneaking through a fitting joint. Not sure it is significant but it is not work the risk.
Would be interesting to see how things stood up.