Crazy? cistern thinking.

Combining a recent you tube video discussing vibration compaction talk about it staying compacted long term with how our first cistern growing up was built.

The compaction video basically said ground compacted properly under buildings was basically the same as piles.  It didn't become uncompacted over time even with ground moisture.  Now I am sure freeze thaw would break it up but what about just water?

Top half of the first cistern in my life was a monolithic pour of the lid and about 4 feet of walls as the top half.  The lower half was a thin layer of concrete plastered over  the dirt.  Bottom half water held fine and worked but it was forever cracking at the joint between the 2 layers.  My parents never did get it sealed for any length of time so we only used the bottom half for the most part.

But what if the thin concrete went clear to the lid so it was a consistent material and the dirt behind it was vibrated or rammed earth thus heavily compacted?  Maybe cob with fiber glass or basalt fibers instead of straw?

I have to admit I cannot work out what you are saying!
Do you have a poorly made water cistern in the ground?

It really depends on if your concrete is reinforced and if the cement is dosed sufficiently. Plain concrete will always crack without rebar reinforcement.

That being said, the cracks are not always terribly significant for something like an in-ground cistern. I built my water tower with nothing but bricks and mortar. It leaks so I just planted banana trees around it...

Musing about cisterns ....

It has been years since I saw a concrete cistern as most are fiberglass now days.

When was the last time you saw one?

Concrete cisterns are still very much in use in the mountains of NC. My grandfather's spring fed cistern (built by my great great grandfather) was the only clean water on his little road (9 houses in a holler) for over a week after Helene came through. When it was built it fed 4 houses and a church. Today, the church has been converted to a house, but it still feeds 3 houses, including one newer one and that church house. I also used to run a summer camp that had a giant concrete cistern that fed the whole camp. It was fed by two large deep wells and served a camp of 400 kids plus staff. I can't remember how many gallons it was, but it had an 8" line coming out of it and it was approximately 80 feet in elevation above the highest point of use.

John C Daley wrote:I have to admit I cannot work out what you are saying!
Do you have a poorly made water cistern in the ground?

I grew up around cisterns.  So I have about 35 years using them.  We had the one small one describe first.  Then we moved to our biggest cistern ever.  It was something like 20,000 gallons.  Octagon  16 feet deep with roughly 6 foot flats making the sides.  Next move we built a concrete block cistern that everything went wrong with.  Lots of lessons in what NOT to do.  We had a neighbor with a cistern that I spent a bunch of time repairing and we installed 2 smaller commercial concrete cistern on the hired help houses. And a friend up country a big for another.  Right now while the crappy dying cistern still exists we put city water in instead of building a new one.

So I am actually thinking cistern multiple directions.  Would still like to have the back up cistern here at the house.   Would love to match our big one is size but even a few thousand gallons would be better than nothing

Then dreaming would like rain catchment.(dry area so smaller)  

Dreaming on a big aquaponics based greenhouse and I would want 3 tanks for this.  2 fish and one hot water storage set in an earth berm as the back wall.  Probably 1 to 2 thousand gallons each.  2 are cone bottom tanks.

Then if the solar planning doesn't do enough want another one for a hot water at both the house and the shop.

Big thing is that if it any of this is going to happen would need to keep the cost to a minimum.  Still trying to find an answer that I think might succeed.  Now the ones doing hot water storage the plastic tanks would not be as valid for.  Ideally want to eliminate plastic too.

recognizing I would need fiber etc with these.  Even wondering if maybe doing it in reverse order needed.  Looking at the cheap version of the underground dome homes Tyvec form, spray concrete with fiber, tight wrap of basalt roving, more concrete, more roving more concrete.  Ends up with rough 1 1/2 inches of concrete.  For the dome homes they then spray it with closed cell foam as the final layer.     What if it was then packed in rammed earth/cob with fiber? either with or without the spray foam?

Or maybe simply rammed earth with or without a concrete plaster with an EDPM or other liner inside.  Less ideal because of the added plastic.

I don't have the answers.  Still dreaming and looking.  But the information suggesting rammed doesn't come uncompacted with water was simply suggesting another possible path for the thinking.  Had never seen anything on this.  So I was posting the question here.

Anne Miller wrote:Musing about cisterns ....

It has been years since I saw a concrete cistern as most are fiberglass now days.

When was the last time you saw one?

 See them occasionally.  Neighbor has one too small.  fiberglass gets really expensive if you want any size and won't work for the possible hot water tanks.

The dream answer would be a cistern made out of glass.  Chemically safe and inert.  So have even been paying attention to the 3D printing with glass.  Almost certainly not doable but still on the dream thinking lost.

That explanation is very helpful.

I would recommend ferrous cement for the projects you describe. Affordable and sturdy. Totally DIY.

Nathanael Szobody wrote:That explanation is very helpful.

I would recommend ferrous cement for the projects you describe. Affordable and sturdy. Totally DIY.

Agreed.  Personally instead of steel looking at doing it with basalt mesh and fiber.  The mesh won't be immediately self supporting and will need to be tied to a support frame for first coat.  But from there should be good.  Big thing is it can't rust and spall which with water projects and thin concrete is a real risk.

/basalt mesh

Huh, I've never seen basalt mesh. Can it be wrinkled up like chicken wire? That's the real strength of the ferrous cement; it is "pleated" with lots of tiny folds for 3 dimensional reinforcement. As for rust, it all depends on how you treat the surfaces of the ciment.

You would certainly be introducing a modern twist to an old techneque.
I guess steel and concrete  about 150mm thick would be great and the new basalt 'steel' is clever, but what is its cost?

C. Letellier wrote:Combining a recent you tube video discussing vibration compaction talk about it staying compacted long term with how our first cistern growing up was built.

The compaction video basically said ground compacted properly under buildings was basically the same as piles.  It didn't become uncompacted over time even with ground moisture.  Now I am sure freeze thaw would break it up but what about just water?

Top half of the first cistern in my life was a monolithic pour of the lid and about 4 feet of walls as the top half.  The lower half was a thin layer of concrete plastered over  the dirt.  Bottom half water held fine and worked but it was forever cracking at the joint between the 2 layers.  My parents never did get it sealed for any length of time so we only used the bottom half for the most part.

But what if the thin concrete went clear to the lid so it was a consistent material and the dirt behind it was vibrated or rammed earth thus heavily compacted?  Maybe cob with fiber glass or basalt fibers instead of straw?

The compaction of the earth will still remain, however, it is not a 'pile' and still expands and contracts with changes in moisture content. The failure of your cistern at the joint due to expansion/contraction differential plus shrink/crack of the eath itself, not compaction. A thin plastering over the compacted earth will never hold water for long, you require continuosly reinforced concrete or suitable liner.

I bet there are some crafty 'natural' solutions to sealing earthen wall or cavity to hold water (fairly) long term. How about firing an appropriate clay content wall material in situ? Or coating the surface with a layer of pitch glue, natural latex, or other durable sealant? Or perhaps a compromise like repurposing an above ground pool membrane or similar?

In my case, I'm in an area with some (already well compacted) non-porous subsoil geology, which leads me to think that simply digging in below grade and capping with some barrier to evaporation would work reasonably well.

To the original suggestion, I think well engineered compacted earth with the right kind and proportion of clay could do pretty well as a tank wall - that's essentially what people do to create pond reservoirs. There would be some seepage, and perhaps unwanted biological activity/buildup to manage.

Vertesol Eustache wrote:[
The compaction of the earth will still remain, however, it is not a 'pile' and still expands and contracts with changes in moisture content. The failure of your cistern at the joint due to expansion/contraction differential plus shrink/crack of the eath itself, not compaction. A thin plastering over the compacted earth will never hold water for long, you require continuosly reinforced concrete or suitable liner.

Now you are talking about part of what I am trying to figure out.  If the tank is round the pressure horizontally is being distributed into an arch.  Vertically built correctly the pressure is applied vertically by gravity.  This means the concrete is under compression both directions and thus working with its strength.  Keep roots away and it should be tough.  What I started with growing up was just a concrete plaster on dirt and worked well up to the transition to the real concrete.  The ability to add fiber to the cement should make it stronger which they didn't have 60 years.  Trying to figure out if it would be enough? would it work on a larger scale etc?  Is it worth trying?

Ben Brownell wrote:I bet there are some crafty 'natural' solutions to sealing earthen wall or cavity to hold water (fairly) long term. How about firing an appropriate clay content wall material in situ? Or coating the surface with a layer of pitch glue, natural latex, or other durable sealant? Or perhaps a compromise like repurposing an above ground pool membrane or similar?

In my case, I'm in an area with some (already well compacted) non-porous subsoil geology, which leads me to think that simply digging in below grade and capping with some barrier to evaporation would work reasonably well.

To the original suggestion, I think well engineered compacted earth with the right kind and proportion of clay could do pretty well as a tank wall - that's essentially what people do to create pond reservoirs. There would be some seepage, and perhaps unwanted biological activity/buildup to manage.

Yes I suspect other possible answers too. Firing clay in situ likely wouldn't work because clay shrinks when fired.  Typically 10% or more.  

But coatings in another thought entirely.  Water glass would close the pores a lot and is food grade.  A number of the natural oils polymerize.  Better answers?

As for pool membranes EDPM pond and pool liners contain an algicide so probably not.  But there is also EDPM rate for incidental food contact.  And I am sure there are others.  Whole point here is to get people thinking.  Also looking for someone who may have tried it and learned lessons to share.

The dream answer is chemically inert, water proof, durable and low cost.  Earthen hole with a concrete liner comes close, if it would work?

As for biology being a problem for drinking water cisterns it would be.  But for aquaponics, or irrigation water tanks probably not.  Gleying is using biology to seal ponds so for a fish tank it might be ideal?  So if we can get close to a seal to begin with would the rest mostly seal of through biologic means?  

If the tank is round the pressure horizontally is being distributed into an arch.  Vertically built correctly the pressure is applied vertically by gravity.  This means the concrete is under compression both directions and thus working with its strength.

T is the tensile force in the tank wall, its in tension, not compression.
This diagram shows how the forces on the tank wall can be shown.

John C Daley wrote:

If the tank is round the pressure horizontally is being distributed into an arch.  Vertically built correctly the pressure is applied vertically by gravity.  This means the concrete is under compression both directions and thus working with its strength.

T is the tensile force in the tank wall, its in tension, not compression.
This diagram shows how the forces on the tank wall can be shown.

You are assuming the water is denser than the wall material and stuff behind it.  Should be very slightly the opposite.  Water is 62.4 lb/ft^3   the wall material should be in the 64 to 100 range.  If so it should push in harder than it should push out.

C. Letellier, I can see what your are talking about, but there is something missing.
Concrete tanks, unlike steel or plastic dont have a history of collapsing inwards, when soil is stacked around the outside.
That may be because the;
- soil is not stacked in a uniform manner, meaning the load is not uniform
- the wall is much stronger on compression