Building a rock/cement water tank

Water tank, horray! Any ideas or thoughts are welcome!

We are building a tank to hook up to be fed by a windmill as well as gutters (we have long dry spells, hence the windmill--plus we have a good windmill sitting around not in use, and an unused well by the house too). In addition we have a dozen 40 gallon barrels we'll attach to each other and attach to the new tank. The water will be used for watering plants, and as emergency-only, to-be-filtered drinking source.

We have a guy who's good with rockwork and has built cattle tanks for us before. Planning to coat the inside with thoroseal. Don't know about a roof--will probably have just a simple tin roof with leftover tin, not air tight or anything.

Our plan is to dig down until we hit rock (we are guessing this will be maybe 1-2 feet--it varies around the property from 2" to 4 feet) and lay the foundation there. From the inner base of the tank (where the water will sit) we'll put a pipe going out one foot up so silt/debris will catch in the bottom and not clog the pipe. Hopefully this will be underground (depends on depth of rock) to avoid freezing. This will go to an above ground faucet pressurized by the water in the tank.

That's the plan anyway. We've never built a tank like this before--is there something we're missing? Or anything that's crazy?

A sheet of EDPM makes a nice reliable seal, unless you let wildlife chew on it. Thoroseal .vs. EDPM - well, neither is manure and grass clippings, which seems to be the only method with the Permaculture (R)(TM) approved seal

The roof does not need to be airtight (actually, air tight would be bad) but if it's not bug tight, you'll have happy mosquitos in about 2 weeks. Insect screening or fish, your call. Fish might be in trouble when you actually use the water, though. I'd guess that shiny roof and minimal ventilation would be best to reduce evaporation.

You should have a drain at the low point with a gate or ball (full-flow) valve so you can flush crud that collects out of the tank. Either use only for cleaning the tank, or use for any "flood-type" irrigation you are doing - and clean the tank while doing so.

Aside from taking "not quite off the bottom of the tank" you'll need extra filtration anyway if you are using drip irrigation or sprayers with small holes.

A siphon-exit is a slight pain to fix the prime on, and means never having to fix the leak around a bottom-exit pipe...

Depending on how tall this is, you might want a section of wire around the inside, embedded in the concrete to reinforce it.

How much does it freeze, that you are concerned with the pipe freezing? - You also need to think about the tank freezing if it's much.

You may find ferro-cement will work better for you than rock with mortar. You Tube has tons of video on the subject of ferro-cement water tanks,

http://www.youtube.com/watch?v=gmdBaFnTwKI&feature=endscreen&NR=1

http://www.youtube.com/watch?v=Xe4EbSdI164 (You may want to mute it however.)

or try these...

http://www.paceproject.net/UserFiles/File/Water/Ferrocement.pdf

http://liveearth.org/en/node/4642

If I had more energy I would go dig up all my ferro-cement stuff I have filed away on this subject, but since I have been really sick for a week, this is about all I can manage. Hope it helps! Oh, one last thing, there is no reason not to go ahead and ferrocement the top too -- you only need a "manhole" and cover for that opening instead of an entire removable roof. If you have a really huge old satellite dish rusting in your yard, you might even incorporate that as a domed tank top. Whatever you do, build a ladder into the design for the INSIDE of the tank. Its a lot easier to drop down into a tank to clean it than it is to get back out once you are there and just remembered you forgot a ladder or rope to get out!

Also you don't need to seal it. Do a really fine finish on the cement and it will seal itself well enough while still allowing air exchange with the water to keep it clean and fresh. It also works like an evaporative cooler to keep the water cold -- which also helps to keep it potable longer.

I use farm fencing and EDPM liners. Super cheap, make the thing in a day. Just make a cylinder with the farm fencing, maybe put in a few posts, then make a ring with rebar or steel wire for the top and the bottom, outside of the posts and fencing. So, now you have a big round pen. Inside, drop in a liner, if you can get one fit to the size (cylinder) great, if not, just get it in there, leave a foot overlap for the edges, then loop a rope around the outside to hold the extra liner. Fill with water.

A complete ferrocement how to on water tanks may be found here http://www.ferrocement.com/tankBook/indici.en.html

Ferrocement liners may be placed in old rock or steel tanks.

Garrett Connelly wrote:A complete ferrocement how to on water tanks may be found here http://www.ferrocement.com/tankBook/indici.en.html

Ferrocement liners may be placed in old rock or steel tanks.

Ahhh... that is the one I was looking for. I lost in somewhere in the depths of my favorites folder. Thanks!

Awesome links and resources everybody! Thanks very much. The tank is under construction. I'll update on this thread if anyone wants to see how it's coming. Hectic schedule right now, but will post soon about details of how it's being built.

Please send pictures of water tanks, septic or successful compost toilets and affordable shelter to contact@ferrocementy.com , where they will be in an archive shared by all.

Garrett Connelly

I realize this is an old post, but I'm hoping there are some folks on here who might still be interested in this conversation.

"You may find ferro-cement will work better for you than rock with mortar. You Tube has tons of video on the subject of ferro-cement water tanks..."

I'm curious if ferro-cement is actually better than a rock water cistern.

I haven't been able to get much information on rock water tanks at all, but the small amount of information I did get, relayed rock water tanks as very durable, and also great to keep water cooler in the summertime. I'm under the impression that a rock water cistern would be much stronger than a ferro-cement tank.

Any thoughts on this? We have tons of rock where we live. We could build about 50 rock houses if we wanted I'm sure. But no water!! So building a sustainable, environmentally friendly (as much as possible) and safe cistern for potable water is foremost in our minds.

Sarah Haas wrote:I'm curious if ferro-cement is actually better than a rock water cistern.

It's different, not necessarily "better". It depends on your needs/goals. A rock cistern is cheaper, but uses more labor and materials. Ferrocement uses less materials, but those materials are more expensive.

They are both plenty strong enough for containing water, if built and designed properly. Rock will likely crack easier than ferrocement, because it doesn't have the reinforcement.

I prefer the cheapest and fastest route, which doesn't include concrete to hold the water. http://velacreations.com/howto/cistern-howto/

Hi Abe,

Thank you for the thoughtful response. I've seen this link before and I'm interested.

I'm curious though why you say it would be cheaper to go the route you mentioned. When looking at the list of materials (such as 5 pieces of sheet metal, 50 ft of angle iron, 50 ft of metal strip, 9 pieces of pvc, 6 pieces of rebar, 18 ft x 18 ft vinyl tarp, etc.) and comparing that to a rock water cistern, it seems the rock water cistern list would be much cheaper. The only materials that I'm aware of would be rock, cement, gravel, sand, and a few smaller pieces for the water outlet/fixtures. Most of the materials I need for that are free. Is there something I'm missing? I'm very aware that there might be. I'm new to this. I realize that concrete can get expensive, but mixing with sand, gravel would make it much cheaper I'm thinking.

My other reason for wanting to build a rock water cistern is: from what I understand concrete can be found with non-toxic materials, therefore would be fine for drinking as long as we filter it. With many other cisterns it looks like the tank would need to be lined with some sort of plastic, which I'm less excited about. Most plastics are going to break down at some point, yes? I realize that concrete is porous and can be a magnet for toxic materials, but as long as there is only rainwater going in and it's well-filtered when used for drinking, it should be better to drink than anything from plastic.

Any thoughts would be fantastic. I'd like to make the best decision for us in the long run, so feel free to play the devils advocate.

What you are missing is that there is a LOT of cement. Cement is not free, and you need a LOT of it. You also need a floor out of the same material, my floor is sand and the liner (which is cheap). The vinyl we use as a protection for the liner, you can use anything free for that.

I've built a lot of tanks, concrete, metal, brick, etc, and the reason why we developed the liner tank was because of cost. Don't ignore your time, either. Time is valuable, and it's a resource that should be considered. A rock tank will need at least 10X the labor as a liner tank.

A lot of plastics don't break down very quickly, especially when they are not in the sun. Concrete in the long run will crack, so you end up lining most concrete tanks eventually, anyway. The most common place for cracks is right at the base, where the walls meet the floor.

I don't agree that concrete is better than plastic for drinking, but that's just personal preference. Rocks can also be full of all kinds of contaminates. Same for sand and gravel, so be careful where you source things.

Seeing as that most plumbing for water is plastic, anyway, I have no problem with the plastic in our tanks. It's the cheapest, fastest way to store rainwater in large quantities.

Good to hear your thoughts. Thanks so much Abe.

I'm going to think this over for a couple of months. I think a huge part of me just wants to play with rocks - they are so beautiful.

But yes, practicality needs to be considered. Romanticizing, in the long run, could be a huge time waster and cause a lot of problems. I didn't think that I would need tons of concrete, but I was wondering. So I really appreciate that info. too.

Awe, but when we are stubborn!

Hopefully, I will make the best decision, which is why I need to hem and haw over it for a few.

Best,
S

At the end of the day, if you get a tank that catches and holds water, that's what's important. Rock, concrete, ferrocement , plastic, and liner tanks all work.

I love rock for certain things, it is a great material. Really beautiful. I try not to lift it over my waist, if I can help it, though.

Another thing you could try is a rock cylinder with a liner inside. This would look nicer than the sheet metal tanks, but wouldn't come with the drawbacks of a rock/concrete floor and seal.

Good luck with it!