I am currently re-reading Ferrocement Water Tanks and Their Construction by S. B. Watt.

I have also reordered Art Ludwig's book Water Storage: Tanks, Cisterns, Aquafers and Ponds from the library.

The ferrocement tank book is for home builders, although other people in the business say that his designs need more support under the chicken wire.

One of the suggestions in Ludwig's book is to buy a large (like 5,000 gallon) plastic water tank and to wrap it with chicken wire and smear on an inch or so of concrete, which protects the plastic from UV and helps to keep the water cooler (most of the plastic tanks seem to be black).

Does anyone have any actual experience with either of these types of tanks?

Sue

I'm not sure pouring concrete around an entire large capacity water tank would be a good idea. Structurally, I doubt a plastic tank could handle that much weight. There's also the question of different materials responding differently to temperature changes. Maybe I'm just being too cautious but then again, I'd rather err on the side of caution when a project of such magnitude is involved.

I think the plastic tanks that were inteded to be buried could handle the concrete's weight, but I might worry about expansion. If had the skills to allow make the concrete shell in pieces and connected them, that might work better.

Is this for an above ground or a buried tank?

Were I to double hull a plastic tank, I would think either a pre-cast vault or a culvert of some sort. How big a tank are we talking about (physical dimension, not volume)?

I wonder if you could cover a platic tank with truck bedliner material?

-Blast

Art Ludwig says in his book that wrapping a tank with chicken wire and smearing concrete over it works, FWIW. The concrete clings to the chicken wire -- most concrete doesn't stick to plastic. I think it's like wearing an overcoat.

Ben, it would be aboveground (soil is far too rocky here for underground). The tanks I've looked at online are 5,000 gallons (just because 6,000 is the max here without having to get a permit). The tall ones are 8.5' in diameter, and 12.5' tall. The short ones are 11.75' in diameter and 7.25' tall.

Blast, plastics don't usually stick to concrete, or not securely, anyway. I use plastic for concrete molds, and don't even need a release agent.

Sue

He might say so but to me, it doesn't sound like a great (or even semi-decent) solution. I can pretty much guarantee you the concrete will crack and chip if applied that way. As you noted, concrete doesn't stick to plastics and the chicken wire won't keep it together in the long run either. Any major temperature changes will make the problem worse, especially if the tank is going to be above the ground. As a matter of fact, the plastics will probably expand much more than the concrete skin so the tank itself might eventually rupture.

YMMV but in my experience I'd try something different. Even if the ground is rocky, burying the tank is still an option. It will just cost more $ and take longer but it will be worth it - far better insulation and the whole setup will be conveniently out of sight. Or if that's not possible, build a standalone shed or concrete box and install the tank inside.

Are you going to use municipal chlorinated water or well water to fill the tank? How do you plan to keep things from growing inside the tank.

It would be cheaper and easier to build a shed for the tank. It will be protected from UV. My experience is that concrete less than 4" thick, whether reinforced with chicken wire or not, is not going to be structurally sound. It'd be like stucko more or less, and won't tolerate encapsulated thermal movement.

If you really want to overcoat your plastic tank, this would be my recommendation:

Polyurea

You can get some excellent UV protection. It has a lot of other beneftits as well, all much better than the concrete and chickenwire approach. I think you'll also find it can be quite competitively priced.

Polyurea is darned near as impervious as it gets. Blast might want to chime in on this, as he's the chem expert, but my experiences with it have all been quite favorable. It is used a lot for ag containment in eastern Washington.

It might be more expensive to do that concrete or not, but a shed seems to be an easier thing to build, if you cannot bury it.

You could also add insulation to a shed to improve the tanks protection from heat and cold.