The Breakroom > The Water Cooler

Another Workshop Time Waster: 3000 Gallon Masonry Cistern

(1/17) > >>

vtsteam:
Following onto Andrew's thread about his pig house construction interfering with his shop time, my time now is mainly going into building a summer drought cistern. I'm continuing since, even though it's been raining lately, the streams still look low to me now, and it is very early in the year for that to happen.

Our water comes from a spring coming out of a small round hole in solid rock ledge. It's been tested and approved by the state testing laboratories and normally feeds a 200 gallon cistern under the house, which is constantly fed and then overflows through a pipe. A shallow well pump takes the water from the small cistern and pressurizes to domestic pressure on demand. There's a 20 gallon pressure tank in the system so the pump doesn't run continuously.

Everything works well, the water is delicious, and cold right out of the spring, and though we've considered putting in a well in the past, the cost of $10,000 or more, and the prospect of not so good water (some nearby wells have sight rotten egg flavors) has made us reluctant to part with our genuine "pure mountain spring" water. We actually get compliments on it from visitors.

The plan is to build a cistern of about 3000 gallons capacity to enable us to weather a drought in late summer. There's always plenty of water in winter.....late summer can pose a problem on exceptionally dry years -- as it does also for some wells in the area. The cistern will be emptied for winter.

The amount of water produced by the spring is huge over the course of a year since flow is slow but continuous, and filling a reserve cistern would be easy with the overflow pipe from the present house cistern.

So anyway, on with the plan. I want it to be shaped like an urn or jug to fit in with the garden, rather than just a utilitary looking tank, and construction will be ferrocement. As a reference I'm using Art Ludwig's book "Water Storage" as a guide The book shows small photos of the construction of one urn shaped tank, but it isn't very detailed, so I'm having to wing it and guess at quite a bit of it.

My tendency is to build a bit stronger where unknown, so perhaps this is a little overkill in construction so far. The base is 8' diameter (unspecified in the book example) using #4 rebar on 12" square spacing. I believe the photos show #3 rebar on wider spacing. Number 3 (3/8" vs 1/2")  is unavailable locally,

The photos also show two shallow trenches dug after the fact of placing rebar, to provide shallow grade beams on a 4" (I believe) concrete base. I will be going with a 6" thick concrete base with no grade beams. I don't like rebar so close to the outer faces in a wet area, and the construction already seems massively stiffened for the purpose.

Actual load is probably going to be in the neighborhood of 600 lbs/sf, and I'm on very good compacted iundisturbed subsoil -- I'm sure bearing is better than 2k lb/sf.

Here's where I am this morning, still adding rebar to the base:

awemawson:
Emptying in winter I assume Steve due to likelihood of freezing? How far below below surface would it need to be not to freeze?

DMIOM:
Steve, I seem to recall from the trouble you had getting access initially, that some parts of the ground were damp. Just a small question - is there a danger of your ferrocement "hull", when fully ballasted-down, moving due to any local gradients?

Dave

vtsteam:
I wasn't real comfortable with the exposed upright rebar like that so first thing this morning i made some blocks from scrap hardwood, drilled them and put them over the ends. There are commercial plastic versions available but I don't have any.




Andrew, yes, I don't need extra capacity in winter, and keeping a full tank freeze free in -10F temps could be a challenge.

Dave, it's currently resting on hardpan, which is the impermeable layer that caused the shop leakage problem The shop is part underground, cut into a hill, above the hardpan and that's the problem. this new tank will not be buried at all,

I'll put a srone retaining wall around it, but with a walk space between. This is slightly graded to allow runoff. Unles the hardpan heaves I don't think the cistern will shift. It could happen however, and the design should be able to handle that, especially empty, without cracking (I hope). It should then settle back in spring, if it moved at all.

Interesting thing about Vermont farmhouses -- they were usually built on a dry laid rubble rock foundation and moved in winter If they did) as if on ball bearings, resettling in spring. Then in modern times people decided to mortar the foundations to lmake them "stronger" and look nice inside, dig out cellars, and or add poured cellar walls. Then had major problems with cracking sills, and foundations falling apart, uneven support stressing structures, water ingress, etc.

So your analogy to a boat hull is not a bad one here. If we keep it intact, assuming it moves, and design our piping to disconnect, and drain the ground around it, movement can probably be eliminated,and if not, tolerated rather than fought against in a losing battle. No guarantees, but that's the philosophy -- we'll see. I've never found that fighting against nature was an easy task, generally I try to let it win without a challenge, and try to fit in.

Brass_Machine:
Even though this is a distraction, I still find the idea pretty interesting (same with Andrew's distractions). They both definitely fit in with the theme of madmodder for sure.

Concrete itself interests the hell out of me. I have been researching it's unusual uses.... Found it in everything from backyard tables, shop benches and even boat hulls! Some of the more interesting things have been full CNC mills made out of a concrete mixture.

I will be watching you build this with enthusiasm.

BTW... I have well water and it tastes like @ss even when I use water softeners with it. To have decent water I use a cooler with jugs of Poland Spring water...

Eric

Navigation

[0] Message Index

[#] Next page