Building Pools, Ponds & Cisterns with Earthbags
Questions answered by Kelly Hart

Q: Is it possible to build water cisterns using earthbags? The idea being that one would construct a large cylindrical earthbag structure with a dome cap atop. If it is possible to build something like this how would one seal the interior so that the water would not seep or the walls would not need constant maintenance i.e. re-application of lime plaster. Is it possible to build this structure both above ground and below?

A: Yes, this has been successfully done, either above or below grade. The easiest way to seal such a cistern is with plastic sheeting, either heavy duty polyethylene or commercial pond liners. It is also possible to use a cement-rich stucco that is virtually waterproof...and there are various coatings that can also be applied.

Q: I am interested in constructing an earthbag cistern. You mention this has been done with success. Can you point me in the direction of any plans or offer any advice?

A: I don't know of any plans for earthbag cisterns, but the concept is really pretty simple. Basically you want to build an earthbag cylinder, making sure to use two rounds of barbed wire between each course. This can be either dug into the ground, bermed, or not...it doesn't matter. Then the best way to seal it would be with a pond liner coming up over the top. The cistern could then be covered in various ways if desired...with an earthbag dome, with ferrocement, or some other roof.

Comment: (Owen Geiger) I'm SERIOUSLY looking into making lots more earthbag tube water tanks. As you know, massive numbers of people lack clean water causing millions to die annually. Our water tank in Vanuatu is looking really good and it will be almost like solid concrete since tamped crushed limestone turns into stone. They're simple to build and teach. People instantly accept the idea, unlike earthbag houses that are more complicated. I think once people start building the tanks they will more naturally consider using the same methods for houses and other structures.

Cost: $200 for 5,000 liter tanks versus $1,300 for plastic ones that can break down, blow away, leach chemicals, etc. The demand is sky high on tropical islands where shipping skyrockets costs. Our process uses very few materials and so shipping is very low cost.

Q: I am wondering if anyone has used the earth bags to build a swimming pool? A friend of ours has a pool built with concrete blocks with a liner covering them. I was thinking that the earthbags would be a great alternative with a much better price. Now their pool is completely in-ground. I would be only able to dig down two feet (really big boulders after that) and then the other two and a half feet would have to be above ground. Do you think this is possible?

A: I didn't build a swimming pool, but I did make a pond by damming a small arroyo with earthbags filled with the local soil and then draping heavy polyethylene over the whole thing. This has lasted some 4 years now. I don't see why this approach wouldn't work for building a pool as well, especially if the pool were circular and several strands of barbed wire were placed between each course of bags.

Q: I am planning to build a number of large (35m3/9246 gal) outdoor water cisterns using earthbags with maybe some rammed earth-tires (foundation only). I would like to use a natural lining both internally and externally. We live in South America where we have intense rainy seasons, followed by a relatively dry summer. I was wondering if you could recommend a natural waterproof lining solution that doesn't involve plastic liners or cement? I was wondering if lime/sand stucco with a number of boiled linseed oil coats would do the trick? These cisterns will likely not go dry completely, and I'm not sure if we should completely put them below ground to help with any moisture escaping through the breathing that would happen with a lime/sand stucco mix (with or without linseed oil). Thoughts please?

A: First of all, I doubt that you really need a rammed tire foundation for an earthbag cistern; the bags themselves serve that function quite nicely. Expecting a lime/sand plaster to hold water over time, even if coated with linseed oil, is asking quite a bit. It might work to some extent, but I would not expect a lime plaster to hold up well over time when immersed in water. If you were willing to experiment with this, and allow some seepage to occur, it might function for awhile...and then if you needed to line the cistern later with plastic you could do this.

C: (Jeff Bousquet) I have often thought that Earthbag domes could make a great cistern. Make a smaller say 8 foot dome with no openings. Have buttresses radiate out from the structure on 3 sides, or better yet berm it. Leave a manhole at the top of the dome. Climb in and ferrocement the inside. Use a rain barrel as a slow sand filter at the top of the dome. This could be make a really low cost water storage system minimizing cement and creating a large water store for irrigation and household needs.

Q: We need to build a water deposit to accumulate irrigation water. Our idea is to do it with earthbags. We envision a circular hole in the ground, 5 yards in circumference, 3 yards deep. Can it be done? Will it hold the water in. Our thought is to put chicken wire on top of the bags and then cover it with cement.

A: Yes, I think that you can build a water deposit in the ground with earthbags. I once constructed a dam for water with bags and lined it with a polyethylene sheet big enough to go up and over the upper edge, and then I protected the top with a layer of concrete. You could also plaster the bags with cement-based plaster, but you might need to coat it with a water-proof paint to keep it from leaking.

Q: My husband and I are researching earthbag home-building for our future dream home here in southern Kentucky. Upon reading "Owen's Philosophy," which accompanies many of the floor plans I've seen on EarthbagBuilding.com, and in which is mentioned the possibility of building a durable and comfortable sofa with earthbags, I became fascinated with this idea of building furniture so that they are organic to the structure, and lend themselves to the "illusion" of a living home. I've also come across a few mentions of earthbag cisterns, and so I began to wonder...might it also be possible to build an earthbag bathtub/shower? If so, what extra steps and precautions should be taken when installing a drain and avoiding moisture damage? Protecting an earthbag home from a wet climate is one thing; I must assume that deliberately exposing an earthbag structure to water, steam, and soap -- or even filling it with water, combined with the agitation of a bather -- requires even more stringent efforts. Right? What say you?

A: Yes, I would say that it would be possible to build an earthbag bathtub/shower. I once built a dam on a stream bed with earthbags, using a pond liner to keep the water from penetrating into the earthbag dam. The same could be done on a smaller scale for a bathtub/shower with several layers of 6-mil polyethylene. I would suggest using cement-stabilized soil in this situation, so that even if the bags did get damp no damage would done. Most likely you would want to use a cement-based plaster over the bags as well, and this could even be tiled if you want.

Q: My wife and I retired to the mountains in the north of Chile. We live on 2.5 acres and are building a water tank out of earthbags for irrigation water. The tank radius is 8 meters at the bottom and 12 meters at the top. It is 5 meters deep. We plan to place chicken wire on top of the bags and cover them with 3 centimeters of cement. The wall of the tank is not smooth, there are rocks protruding in some places. We did the best we could with what we had. The idea is to follow the contour of the walls with the bags, in other words the bags will not be in a vertical position but they will be leaning on the widening wall. The question is; will it work?

A: That is quite a large cistern you are building! From your description, I would say that your plan should work. The bags will be acting as a retaining wall for the excavated cavity, if I am picturing it correctly. The fact that the walls lean outward is a definite advantage in terms of stability. I suggest that you do use the two strands of barbed wire between all of the courses of bags to help keep it as monolithic as possible.

Your main challenge will be obtaining and maintaining a waterproof interior coating (including the base of the tank). Using chicken wire mesh (or even a plastic stucco mesh, which might last longer in a damp environment) is a good idea to keep the plaster intact over time. I suggest a mix for the stucco that is very high in cement, as this will be more waterproof. You might research ferrocement cisterns to get an idea for what is appropriate. Then you might also consider an additional waterproof coating over the cement (something like Thompson's Water Seal).

Q: I read that you built a dam a few years ago with earthbags and have encountered zero problems. I have been wanting to attempt a very small pool, approximately 40 square feet and only 3' deep. Could this work with earthbags? I was thinking of using lime instead of concrete followed by Elastomeric (rubberized) paint. What would be your thoughts on this?

A: Yes, I did build a small dam with earthbags about a decade ago. The pond unfortunately was inundated with a massive flash flood that filled it up with sand and silt and it was never dug back out...but I'm sure that the dam is still intact. Is your pool above or below ground? I think it is possible to use earthbags either way. The pool I made was lined with a sheet of 6 mil plastic, with gravel or stone place over it to protect the plastic from abrasion and UV deterioration. The rim of the dam had mortared stones protecting it. Would lime and Elastomeric paint work to seal the water? It might. I suggest some trials to make sure before treating the entire pond area this way.

Q: We live in the Maldives Islands. Since our island is low-lying and since the sand is loamy it is difficult to dig a well and keep the sand from caving inl. Therefore we thought if we could get earthbags to put on the side of the well after filling them with sand then probably we could secure the water in the well without making a concrete well. What do you think?

A: Yes, I think what you suggest is possible, especially if you keep the well circular, like a cylinder as it goes up. Polypropylene is not affected by moisture, so that shouldn't be a problem. You will need to protect the material from sunlight, however, so perhaps a cover for the well is a good idea. Without being plastered, the bag wall will probably be porous and allow some of the water to escape. A more secure surface could be made with mesh-reinforced cement-based plaster.

Q: The main reason we have created our earthbag jacuzzi is for our rain water collection and it will go into the house and be a part of our grey water system. We plan on sealing the stream catcher/jacuzzi with either linseed oil or another non-toxic sealer; any suggestions?

A: I can only suggest some experimentation. Linseed oil is a good place to start, as it is a hardening oil and can render plasters fairly water resistant. You might make some small bowls that are plastered and sealed in various ways and see which ones seem to hold up over time when filled with water.

Q: For an above ground swimming pool is it possible to use earthbags? Considering a pool can house 20,000+ gallons of water, let's say the surface is leveled but isn't back filled at all, would an earthbag structure without any additional backfilling or support withstand 20,000+ gallons of water?

A: Yes, earthbags have been used to create above ground cisterns and pools. I used them to made a dam once. Be sure to use two strands of barbed wire between each course of bags and use a good plaster mesh embedded in a cement-based plaster. A circular design is the strongest.

Q: I want to build an in-ground cistern with earthbags. I am thinking a round, maybe around 2m diameter (or square?) structure. Will the walls need to have some kind of outward leaning to resist lateral forces?

A: If you keep the tank circular it should be more stable in withstanding forces both inward and outward, so that is what I would recommend. In this case the walls can be vertical.

Q: What I'm ultimately hoping to do is to use bags to create an inexpensive natural swimming pool structure. The swimming area would be up to 20ft wide and 30ft long, 10 to 12 feet deep on one side and maybe 3feet deep on the shallow end. In your experience do you think it would be possible to build below-grade, vertical walls of this height using sandbags? I would then use a giant pond liner with some sort of underlayment to protect it. I always envisioned smooth walls, but would this be possible using bags?

A:  It is generally more stable to have the walls of an in-ground pool slant outward, but this is not absolutely necessary. If the pool is rounded that will help make it more stable. Because of the outward force of the water contained, vertical walls can be relied on to remain standing, and 10 to 12 feet deep doesn't seem unreasonable. Yes, you can finish earthbag walls to be quite smooth.


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