Leaking Large Concrete Fish Pond

[SausageKing]

I have a large concrete fish pond with 30cm thick wall and 60cm thick floor. 1.5m deep x 4m wide x 7m long. the problem is when i fill it up the water goes down by a 1/3 in a few days ? I canot find damage or any holes ???? anybody got and ideas, I feel it maybe sucking water through the concrete ?? i was told the concrete had an agent mix with it to make it water proff ?? ummm

[Thailaw]

You might consider having the interior tiled, which should stop any water leaking through. It should not be an expensive job to have done. I have a fish pond a bit smaller than yours, with vertical sides and a flat bottom. The entire pond and surrounding area is tiled, and I have no loss of water from leakage, although I do lose an inch or two every 2 or 3 days due to evaporation.

[trogers]

...30cm thick wall and 60cm thick floor...

What is this concrete shell sitting on? A 60cm thick mass of concrete weighs about 1400kg/sqm excluding the weight of water and the weight of the wall at the edge.

Normal soil can only bear weights of 1300-1500 kg/sqm.

[fdimike]

The easiest solution to the problem is to drain the pond and let the concrete dry a few days. Then coat the concrete with a WATER BASED concrete sealer such as Bosny Water Seal. This product is available at nearly any building supply company here in Thailand such as Home Pro or Global House. It may also be available at paint stores. The product is very easy to apply and will permanently seal concrete preventing water loss. This product will penetrate the concrete and if applied correctly is not visible like paint. It also will not peal off like paint as it becomes part of the concrete. The directions suggest two coats be applied. Concrete in itself is porous and will allow water to pass through it. I suspect the proper amount of waterproofing compound was not added to the concrete mix at the time it was built.

I hope this helps.

[thaimat]

Bentonite clay can simply be added to the pond without having to drain it. It forms a good seal on the bottom, and is certainly easier that draining and cementing, or draining and tiling. Google it, and you'll see it's used in fish ponds all over the world. There's also a company in BKK that sells waterproof membranes, a liner that covers the bottom and does not allow water to pass through. www.yangma.co.th Khun Thitiwat is a good guy there, speaks and write English fairly well, and is interested in green solutions whenever possible.

[fdimike]

Thaimat

I think you have some interesting suggestions however I suspect the clay will not solve the entire problem if you cannot apply it to the sides of the pond.

Installing a waterproof membrane on a large pond like this will not be easy. This membrane will have to cover the entire pond (bottom and sides) to be of any value. Intalling a membrane such as you suggest with the water still in the pond will be very difficult as the membrane will not easily conform to the shape of the pond. The membrane is designed to be used in a dry pond (either concrete or dirt) which is then slowly filled with water and adjusted to the shape of the pond. The weight of the water will keep the membrane pressed tightly against the concrete. The part of the membrane which goes over the top edge of the pond is then typicaly hidden from view with flat rocks and plantings. Another drawback with membranes is longevity. These membrane will only last "X" amount of years before the sun breaks them down. A membrane with a long life span to for a pond this size will also be expensive.

I still maintain that the easiest most effective & least expensive way to seal the concrete is by emptying the pond first and then seal all the surfaces with concrete sealer which has an indefinite life span and is relatively inexpensive. The fish and any plants can be removed and placed into temporary containers until the sealer is dry (1 day at most).

Edited April 30, 2011 by fdimike

[thaimat]

Well said FDIM, I agree with you to a point. But I would question the "indefinite" lasting power of the sealer, as it's longevity is controlled to a great degree by how much is applied, (they tend to use materials like this here, in the smallest possible quantity, so that longevity comes into question), and the PH levels of the water. Highly acidic or highly alkaline water will eat through even concrete sealer. The chemical makeup of the sealer would give me pause because of how it would affect the PH of the water, and what kind of nasty toxicity it might have, both of which could affect fish and plant health and growth. Membranes now have a life expectancy of 30-50 years, which should be long enough, I would think. Whether a membrane or concrete sealer was used, the water would have to be drained. Bentonite clay does adhere well to the sides of a fish pond, if the sides slope outward, and an advantage is that the water does not need to be drained, in fact must not. Disadvantages of Bentonite could be the cost here, and the fact that you have to be aware of what plants you grow in the water, so as not to allow roots to penetrate the clay long term.

I have no commercial interests whatsoever in any of these products. Were this my fish pond, I would be looking for: a long term solution that isn't based on a perfect job by local workers, (like that happens so often); materials that have unknown and possibly toxic ingredients; a solution that doesn't spike the PH, which would directly affect the longevity of any waterproofing solution; and a solution that doesn't negatively affect, indeed adds to the quality of the water for both fish and plant health.

Thaimat

I think you have some interesting suggestions however I suspect the clay will not solve the entire problem if you cannot apply it to the sides of the pond.

Installing a waterproof membrane on a large pond like this will not be easy. This membrane will have to cover the entire pond (bottom and sides) to be of any value. Intalling a membrane such as you suggest with the water still in the pond will be very difficult as the membrane will not easily conform to the shape of the pond. The membrane is designed to be used in a dry pond (either concrete or dirt) which is then slowly filled with water and adjusted to the shape of the pond. The weight of the water will keep the membrane pressed tightly against the concrete. The part of the membrane which goes over the top edge of the pond is then typicaly hidden from view with flat rocks and plantings. Another drawback with membranes is longevity. These membrane will only last "X" amount of years before the sun breaks them down. A membrane with a long life span to for a pond this size will also be expensive.

I still maintain that the easiest most effective & least expensive way to seal the concrete is by emptying the pond first and then seal all the surfaces with concrete sealer which has an indefinite life span and is relatively inexpensive. The fish and any plants can be removed and placed into temporary containers until the sealer is dry (1 day at most).

[trogers]

The suggestions on sealer or membrane, or bentonite assume the presence of leaks.

The first question should be the reason for these leaks. The thicknesses of the concrete shell are unusual and too massive to be supported by normal soil and without piles. Are these leaks resulting from cracks in the concrete shell due to excessive and uneven soil settlement. The latter has to be addressed before even discussions on methods of waterproof.

[fdimike]

Trogers

I would have thought cracks would have been the first thing Sausageking would have checked for. My suggestions were based on there not being any cracks.

Thaimat

Your suggestion about the membrane is fine but a rubber membrane that large will be very expensive. I would suspect a Firestone butyl rubber liner that size would cost about $3-400 in the US. I have no idea what it would cost here.

I specifically said to use WATER BASED concrete sealer. This will have no effect on the Ph or any living organisms as far as I know. I have used similar products in the US on a concrete Koi pond with good results. I'm using the same concrete sealer in my salt water swimming pool right now to seal some concrete decorative immitation beach sand which remains constantly underwater. Obviously you can't use sand but you can make concrete look like sand very easily. It works just fine and has had no effect on the Ph or water clarity. the instructions call for 2 coats to be applied by brush or roller.

As for longevity I would say we're talking 20 years under the best conditions. The sun here is especially destructful since we are so close to the Equator.

[bbradsby]

Normal concrete passes water at a microscopic, capillary level; it is a porous material. The fluid-applied, crystalline waterproofing will seal off capillary water passage through concrete, and may close off hairline cracks. I don't remember, frankly. But it won't bridge movement cracks or shrinkage cracks in concrete. Note: ALL concrete cracks. Also, tiling a moving concrete substrate will only transfer those cracks to the tile system, and leak.

I'd recommend draining the pool/pond and having it inspected for cracks and download material data sheets from manf websites to see their products' applications & limitations. If you have cracking, then a membrane of some sort must be added, and there are a number of types - sheet & fluid applied. But be aware that cracks can puncture a membrane under the pressure of the water depth. Take your time, do your homework, and hopefully do it only once.

All the best,

[WarpSpeed]

The suggestions on sealer or membrane, or bentonite assume the presence of leaks.

The first question should be the reason for these leaks. The thicknesses of the concrete shell are unusual and too massive to be supported by normal soil and without piles. Are these leaks resulting from cracks in the concrete shell due to excessive and uneven soil settlement. The latter has to be addressed before even discussions on methods of waterproof.

Not according to your own figures, it falls right within the support parameters.. Don't see the average fish pond being overweight for the surrounding soil to support it if it hasn't been seriously over dug and the ground remained naturally compacted prior to installation..

Edited August 19, 2011 by WarpSpeed

[WarpSpeed]

Trogers

I would have thought cracks would have been the first thing Sausageking would have checked for. My suggestions were based on there not being any cracks.

Thaimat

Your suggestion about the membrane is fine but a rubber membrane that large will be very expensive. I would suspect a Firestone butyl rubber liner that size would cost about $3-400 in the US. I have no idea what it would cost here.

I specifically said to use WATER BASED concrete sealer. This will have no effect on the Ph or any living organisms as far as I know. I have used similar products in the US on a concrete Koi pond with good results. I'm using the same concrete sealer in my salt water swimming pool right now to seal some concrete decorative immitation beach sand which remains constantly underwater. Obviously you can't use sand but you can make concrete look like sand very easily. It works just fine and has had no effect on the Ph or water clarity. the instructions call for 2 coats to be applied by brush or roller.

As for longevity I would say we're talking 20 years under the best conditions. The sun here is especially destructful since we are so close to the Equator.

Yes Mike reasonable assumption but in my mind a 3rd of the water is a high volume of water in a short period so I believe it may be related to a pipe fracture especially if no visible cracks are present as one the size to allow this much loss should be pretty obvious.

If it's possible he should shut down the system and shut or block all of the pond plumbing (hopefully he has valves to d it with) assuming he has a buried circulation system, mark the level with a pencil, check in 24 hours barring rain of any amount, if it slows or stops significantly it's likely to be a pipe. Then if it is a pipe open the system back up again and let it stand static with pump off for 24 hours. When it loses, measure it from the original mark and then try again with the pump on and if it loses more water then off the leak is on the pressure side of the system in a return somewhere, look for weak points like where 90's have been installed.

If it slows when you run the pump the leak is in the suction side of the pump and it may draw air when it runs instead of leaking water out but either way it will slow the loss unless the crack is actually cracked against the direction of the water flow which will force more water out as it is forced into the crack. If it is in the direction of the waters flow the rate of leakage will decrease when on the suction side as the pump will be pulling the water over the crack at a rate of flow that will prevent much loss and with suction into the system..

JFYI draining a pool/fish pond or any water containing vessel to discover a leak is counter productive and like chasing your tail. The leak should be definitively located while water is in the pond and then repaired accordingly anything else is just guess work..

Edited August 19, 2011 by WarpSpeed

[WarpSpeed]

I just realized that I mentioned valves in the above post but valves will not isolate the various pipes completely as water will be coming from both directions in a static system once the pump is off.. So it is necessary to block off the pipes from both ends this can be done with plastic (I.E. cling wrap or even condoms over then ends preferably new ones and tied tightly), skimmers and if a main drain put over the top with a brick or some flat, heavy object to hold it down level.

If this stops the water loss then it's possible to poke a small hole in these one at a time and put a small amount of dye like Cl2 indicator or even better Ph if you have liquid and not strips or can buy one for this purpose just in front of the hole and watch it closely to see if it has influent flow or just kind of floats around the opening.

If the system has been off for 24 hours it would be sufficiently dried out if leaking so the minute you poke the hole it may even bubble air out and the water should flow in with quite a distinctive pace to it and will not stop, like the pump is sucking it in. Basically what you've done by this procedure is reduce the size of the leak to this one small hole you've created though the actual crack is probably much larger so it should have a very distinctive influent flow that would be hard to mistake..

[pgangell]

I have the same problem and have approached the people in the add accompanying the forum backyard-pond.justanswer.com. They made the following comments which I thought may be useful.

1. Bosny Water Seal is mainly to seal surface masonary and is not meant to cope with the strains of a big fish pond.

2. The product they mentioned to do the job is Herco No. H-55 Neoprene Rubber coating - their web site is http://hechtrubber.com/Pages/KoiLink.htm?gclid=CM6ZgZnBlKwCFQtU7Aod_xN_pg

I have asked Hech Rubber how to get their product in Thailand and am waiting for an answer.

[pgangell]

Bad news. They only supply to US. How then is an Aussie adviser recommending this? I am going to give Bosny a go.

[dereklawler]

Buy a bag of hydraulic cement...mix it stiff a little at a time...put a ball of it in your hands and knead it till you fell it heating up...jam it onto the leak and hold it there while trying to work it in the leak...repeat till the flow stops...