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Doug Hoover
Title: Koi Ponds - Dispelling Myths About Concrete Ponds
Summary:  An experienced construction contractor provides his "secret formula" for success in using concrete for waterfall and pond construciton.

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Koi Pond: Dispelling Myths About Concrete Ponds

By Doug Hoover

What do some liner promoters and salesmen say about professional pond installations using concrete and rebar, plus mortar to hold the rocks?

(1) "One problem with concrete and mortar construction is that of cement alkali leaching out for some time after construction, poisoning the pond water with high alkalinity. It also leaves unsightly white deposit build-ups at the points of exit and on the surface of rocks in the waterfall."

NOT TRUE! If the concrete you use to pour the shell is a 7-sack mix with 40% pea gravel and stealth fiber mix, the concrete is so dense that no leaching can even occur. Also, because of the density of the concrete, it is not only waterproof, but stronger than normal 5-sack mix used to pour driveways, patios and sidewalks. Finally, if you coat the finished surface with Thoro-seal, one of several non toxic concrete sealers, it cannot leach.

(2) "When you use mortar mix to secure the rocks in a waterfall, the water that soaks into the porous mortar joints, leaches out alkali and phosphorescence that poisons the pond.

TRUE in the past, but not anymore. Regular mortar is porous, allowing water to pass through, dissolving and collecting the cement residue. This had been a major concern of mine for many years. After the completion of a waterfall, I would have to run the waterfall for two or three weeks, shutting it off every 4 or 5 days, and acid-clean the white alkali residue off the rocks that had built up. Then, when we were finished, we would have to acid clean and rinse out the pond.

Twelve years ago I discovered a secret formula that would render the mortar mix non porous and waterproof. It also makes regular mortar mix three times stronger. It is produced by adding one 45# bag of thinset (used to apply ceramic tile to a shower wall) to two bags of type S mortar mix. Once it cures, it becomes so dense, it is totally waterproof and will not leach any alkali after it cures (3 to 4 days). In addition, this mix is so strong in its holding ability that once it cures, a sledge hammer is needed to remove a rock. In most cases, the rock breaks up before coming free from the secret formula mortar.

It is not only waterproof, but it bonds very well with all types and textures of rocks. It will create a watertight barrier that comes in handy when building rock damns in the waterfall. The main feature of my special formula, is that it allows for much more creativity. You have the ability to raise the water level above the confines of the concrete shell without water leaking through the mortar joints, as in the case of regular type mortar mix.

This special mix is not for sale in the stores, and never will be, because I give the formula away for free! This discovery has revolutionized the effectiveness of mortar mix and its ability to bond, waterproof, and prevent alkali leaching.

A Dramatic Test

A 4,000 gallon swimming pool was converted into a concrete koi pond with two large waterfalls, held together with my new mortar mix, and an 8' x 12' island. The rocks surrounding the island, were also held by the new formula. When the project was completed, all the surfaces were given a quick, mild acid wash, and the pond was filled and dechlorinator was added. The following day, $3,000 worth of my own personal koi fish were transferred into the concrete koi pond. They all swam calmly around the island, inspecting every nook and cranny. None of them experienced any stress and they remained in their temporary quarters for three months with no incidents. If that dramatic demonstration was not enough to convert the skeptics, nothing will.

So what is the bottom line?

Pond liners cannot be guaranteed not to leak, for a myriad of reasons. Concrete and rebar ponds, if built properly, will stay leak- free for decades, if not generations. You be the judge. You're the one investing your hard earned money and time into it.

Below you can follow a concrete waterfall and pond construction, from beginning to end.

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Site prior to waterfall and pond construction

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Another photo of site prior to waterfall and pond construction


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Pre-construction, digital design photo one


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Pre-construction, digital design photo two

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Excavation of the waterfall and pond site


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Laying of concrete


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Laying of concrete and rebar


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Finished waterfall and pond

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Another view - finished pond


Be as wise as an owl and as sharp as the many objects that can puncture a liner shell. If you have any questions:

Happy koi, peace & joy.


About the author:

Doug Hoover

Douglas Hoover, with his wife Alice, has resided in San Diego, California, for twenty-five years. Previous to settling in California, he was a custom home builder and designed and built restaurants. He designed and built one in Michigan; he built the first two of a chain of Pony Express pizza stores in Provo and Salt Lake City, Utah. In La Jolla, California he built two restaurants on Fay Avenue, The Bagatelle French Cuisine and Pizza Jolla Italian Restaurant. Doug Hoover has well over 1,900 waterfalls to his credit. The largest of these is 135 feet high on Mt. Soledad in La Jolla. His experience includes dozens of waterfalls constructed to spill into existing swimming pools, waterfalls for pool contractors, the conversion of swimming pools into koi ponds, and more. His work stretches from California to the midwest.

Doug Hoover is also an inventor of several pond products such as FountainliteTM, FountainPotTM, AquafillTM electronic float control system. There is now one available for new swimming pools and a retrofit model for existing pools. Also there are Aquafills for hot tubs, ponds and fountains of all types.

Doug Hoover's work has appeared on the front cover of many magazines, including Ponds, Ponds USA, San Diego Living, San Diego Family, San Diego Home and Garden, Living in Style, and the May 2005 issue of Better Homes and Gardens "The Spring Planting Guide." He was on the front cover of the October, 2003 issue of San Diego Home and Garden and that project won "Garden of the Year" award. Doug currently is a free-lance writer for six magazines and is the author of a first-of- its-kind construction manual for contractors that teaches every aspect of professional waterfall and pond construction. Doug is an expert author and his articles can be read at