Sealing a new concrete pond

leubafr(z8/9)February 6, 2009

Hi all, my husband and I are new to ponds but we knew we wanted one. Since the cost of rocks was so much that we really could not afford it, we decided to do it in concrete. I know, everyone discourages you about concrete.

Our pond is 18'x8'x3'. Sort of oval. To keep the concrete from leaching into the water, we ordered the pond sealer on the web. It was VERY expensive (1-1/2 gal) and did not cover the area that was advised it would. Also it was hard to work with. Being a former crabber and fisherman, my DH went to the boat shop and bought a gallon of fiberglass sealer that you use on boats, etc. He applied it with a roller, and it dries in 20 min. Put on three coats from one gallon waiting at least 20 min between coats. The next day we filled the pond with water and put in our fish.

That was right around Thanksgiving and we have not lost a fish yet. The eco is wonderful and we are just so excited.

I wanted to share this with you guys because I keep reading that you're worried about the concrete leaching and killing your fish. We do have a waterfall that is not sealed. Bought our pump and filters on line.

It has been, and still is, a wonderful experience. Can't wait for the warm weather so that the plants we have will begin to grow more.

Leubafr in S.E. Louisiana

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Hi Leubafr and welcome to the ponding addiction. I started off with a small concrete pond inside our greenhouse. Concrete and limestone = high ph and hard water. I learned our water is high PH(8.5-9) right out of the tap. That makes even low amounts of ammonia in your water toxic to your fish. Our water company also adds chloramine to our water (chlorine and ammonia). Test your water. When you add water use something like "Pond Prime" to detoxify the ammonia. It has made a world of difference in the health of our fish.

    Bookmark   February 7, 2009 at 8:46AM
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Thanks for the information. I will check the ph and make sure that it is well within range. We do have chlorinated water but it is only added a little at a time to make up for evaporation. We are loving it! Fish are responding to the warmer weather very nicely too. They are just so much fun to watch.


    Bookmark   February 8, 2009 at 12:30PM
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horton(6 b Ontario.)

leubafr Welcome to the wonderful world of ponds.
It sounds like your husband knows what he is doing by using the fiberglass sealer,as long as you allow it to cure properly, it does a great job.
When that warm weather arrives,please hurry it on to us up north, we could do with some mild temperatures.
Enjoy your pond,

    Bookmark   February 9, 2009 at 7:16AM
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Thank you Horton, and yes, we are really enjoying our pond and the fishes.

The warm weather is come and go. Last week it was below freezing at night and in the 50's during the day. This week it is in the 60's at night and high 70's during the day. That's why we stay sick. BUT, it is great
Mardi Gras weather. I love it when it is warm for the parades. I will try to push it on up north for you guys as long as you will try to push down some of your cool in the summer.

Thanks again,

    Bookmark   February 10, 2009 at 11:18AM
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basilbird(z6 RI)

Oh Mary,
I wish I had your warm weather! I have a cement pond that has cracked the past two winters. Last year wasn't bad but this year has been disastrous! Going to have to take all the little fishies out and re-do most of the low end. Hopefully I'll get it right this time!

Apart from the cracking problem, I love my cement pond. Mine is coated with a couple of layers of UGL DryLoc. I haven't noticed any Ph problems. This time around I'm thinking of using a different sealer. Have you heard of Pond Armor? I don't think it existed when I first built the pond 4 years ago. It *is* expensive but ... hey... if it works!


Here is a link that might be useful: Pond Armor website

    Bookmark   February 10, 2009 at 2:51PM
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Hi Basilbird,
yes, I have heard of Pond Armor. That is the first sealer we bought. It was VERY expensive and did not go as far as it was touted. The people at Pond Armor are very nice and helped us quite a bit. We ordered 1-1/2 gal. to cover our pond (to their specifications) and it only covered about 1/3 of it. That's when we went to the fiberglass sealer. It went on wonderfully and dried quite fast. You can purchase it at a reputable hardware store but we got ours at the boat shop. My husband used to crab and do softshell crabs. This is what he painted the wooden boxes with to keep them from rotting. Works very well.

Good luck and let us know what you decide to use.

    Bookmark   February 10, 2009 at 4:35PM
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I have used Pond Armor as well. It is a bit pricey and you still have to do a lot of caulking.

I am curious about the fiberglass sealer. When it dries is it clear? I would be interested in a product that dries to a clear finish.


    Bookmark   February 10, 2009 at 4:39PM
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YES, the fiberglass sealer dries clear. You can see right thru it so well, if you didn't know it was sealed you would not see it. It is very inexpensive compared to the Pond Armor. Wish I had used it exclusively.


    Bookmark   February 17, 2009 at 11:37AM
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I would think the fiberglass would crack when frozen just like the concrete does. Has anyone tried liquid EPDM? Just a thought.


    Bookmark   February 17, 2009 at 10:55PM
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I think you may have hit on something with the fiberglass repair option. Could you tell me the name of the product that you DH used? I have looked at the HD & L but I can't find what you are refering to. I realize that I may have to go to a marine supply store but I would like to know what to ask for.

I am having a leaky waterfall and was thinking that this might be a perfect solution. Also, do you think that using fiberglass cloth would be beneficial as well?

I have never worked with fiberglass sealer before. Is it difficult to use?


    Bookmark   February 18, 2009 at 3:51PM
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basilbird(z6 RI)

Frogman... I think you are probably right about cracking but I would imagine hair line cracks would remain sealed. I'd guess the same is true of Pond Armor. And, of course, it is fairly easy to patch fiberglass. Mary is in Louisiana so (assuming her cement cured well) she shouldn't have the serious cracking issues I have in the North East.

I have heard good things about liquid EPDM (except that it's **expensive**!). Even that, though, can't hold water back from a serious crack.

I'm trying to tackle the cause of my cracking - frost heaves. Now that I understand it a bit better I'm amazed at how high much of the ground in my backyard has come up this winter! I was walking around on the "top" and breaking through 4 or 5 inches! Water and ice are really, *really* powerful things!


    Bookmark   February 19, 2009 at 6:58AM
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Frogman. . . DH says he bought the fiberglass resin in the paint dept. at Home Depot. You can also go to a marine supply. It is not that expensive. Much much less than the Pond Armor product. Also, the fiberglass cloth would be a good idea too, since you have cracks. One coat of resin, put down the cloth, then two or three coats over the others. Would be just like a swimming pool or boat. Voila' Our concrete pond doesn't require rocks in the bottom and is beautiful (like a swimming pool). So easy to keep clean. If you would like, I will send some pictures thru regular e-mail. I don't know how to insert pics on this site.

I don't have the freezing temps you guys have up north but it does freeze here. We need it to keep down the mosquito population.

    Bookmark   February 19, 2009 at 1:13PM
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i was think of useing it this myself as all the other things i've looked at for 2 weeks on here are not any better and i think most will cost a lot more . can you tell about how must gal cost as my pond is 18x10x 2.5 that close to yours i have cloth and matt to so i just need to get some resin thinks for the input.

    Bookmark   June 12, 2009 at 12:43AM
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does the fiber glass sealer stop pond from leaking?

    Bookmark   July 14, 2010 at 12:57PM
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Hi Lucille pond, I am not sure but probably will if you can get enough down into the crack. Otherwise, fill the crack with something else and then cover it with the sealer.

This past winter was very cold here in S.E. Louisiana. We kept our pond pump running round the clock but with all the rain and extremely cold weather, we developed a crack in our waterfall. DH put the foam expander insulation down into the crack. Twice. It is stopped for good. Just put another rock over it to cover.

    Bookmark   July 14, 2010 at 1:55PM
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FYI: I want to post an update to this posting. We have had our pond running for 1 1/2 years now and have not lost one fish. Several of you were concerned about it being a concrete pond and then using fiberglass sealant over the concrete. Wondered if it was a potential hazard to the fish.

I can attest to the fact that we have very healthy fish and we have not lost a single fish since we started up. Remember, you can buy the fiberglass sealant at stores that sells boats and/or boat products.

    Bookmark   July 14, 2010 at 2:00PM
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jeff_in_wi(z4 WI)

We had a concrete pond at our old house. We didn't put it in ourselves - it was there when we bought the house - so I don't know if it was sealed with anything or not. We lived there for 19 years and never had any issues it it leaking or cracking. Even with 30 degrees below zero (F) winters and up to 105 (record temp in 1995) in the summer - NOT ONE SINGLE PROBLEM with the concrete pond.
I did have a few leaks in the waterfall I added though.


    Bookmark   July 14, 2010 at 3:29PM
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Is anyone still here, that could answer a question about using Fiberglass resin? I read a few suggestions from others about using this for the bottom of a pond, and that it worked great. I'm wanting to find a sealer for my painted/decorated birdbaths. It seems like I can't find anything that doesn't turn white once water has been in for a few days.
Any thoughts on this I would appreciate it, or even your own idea's.

    Bookmark   May 13, 2011 at 11:03PM
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This post was VERY helpful. We are newbies to th epond world and had no clue about the concrete. We put in the fish and of course the PH was super HIGH. We then googled and figured out it was the concrete because it wasnt sealed. We will be headed to the store to buy the fiberglass resin and cant wait to add our fish back to our new pond. the poor fish have been living in a large white fishing cooler.

    Bookmark   August 10, 2011 at 6:22PM
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Well, I think in general epoxy and fiberglass resins are not going to kill fish unless you introduce them too quickly after the application. Once, the coating is completely cured (72 hours +) then it is safe. Now, some coatings go that extra measure and become approved for animals and potable water, etc...
It sounds like the concrete job done by jeff_in_wi'S PREVIOUS OWNER was a well cured and sealed pond. Leaks occur when concrete cracks from the reaction of rebar with chemicals, or because of expansion from varying temperatures, etc....So, it is very common for cracking to occur over time. These cracks will allow leaks to form because the sealer and concrete is displaced.
This is where a flexible sealer/membrane is a great solution. You can use these which are similar to a sealer like this topic, but there is a flexible component that creates a membrane that resist cracking when the underlying substrate cracks. It's not a polyurea, but a polyhybrid. There's seal tite coating from spray-lining and then there are soft polyureas, but they can't really be done by yourself because you need very expensive equipment to apply it unlike the seal tite product.

So, the point was, great idea on using the boat resin. It would more than likely NOT kill the fish. But, it's always good to KNOW that the material is indeed safe for animals. That's all about VOCs. But, to step it up a notch you can check out the polyhybrid solutions out there. Many times, concrete is not cured and sealed properly ending up in leaks at some point during the lifetime of the pond. And trust me, that is a BIG PITA.

list of VOC List included so you can check it against the MSDS.

Here is a link that might be useful: VOC List

    Bookmark   August 18, 2014 at 2:46PM
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basilbird(z6 RI)

So odd to see this ancient post (with my name buried in it) resurface again!

For what it's worth, I finally sealed my pond once and for all with Permaflex and Liquid Rubber:

Total cost was around $500 and the products are totally fish safe They are even used in zoos. Just be sure to follow the instructions! That means a totally clean cement surface with NO previous paint layers. The liquid rubber expands and contracts during even the coldest weather and the permaflex seals everything else

Here is a link that might be useful: Permaflex

    Bookmark   August 20, 2014 at 1:24PM
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Cool. Thanks. The sanitred product looks pretty similar in function to the one that I mentioned. Both look great. I like the color of the sanitred. seal tite products I think have shades of grey and blue only.

BTW - I found this page like #1 on google for "how to seal a cement pond."

So, I guess you're total sq ft was like 310 sq ft?? That's like $1.60 / sq ft.... that's cheap. I think that Seal Tite is a 30-40 mil coat and is more expensive. How thick did you coat your at? I love that sanitred mil height caluclator. Seal Tite is very upfront about the importance of that as well. Great info, thanks.

Here is a link that might be useful: About Mil Height for Spray-Lining

    Bookmark   August 20, 2014 at 1:43PM
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basilbird(z6 RI)

Nice to see Sanitred is #1 in the Google search! I wish that had been the case 6 years ago when this thread was started!

The thing with Permaflex is that it's really thin - strong, but thin. I did two coats but it doesn't have much of a thickness. It's the liquid rubber (the blue stuff) that has thickness and stretch. The other thing is that what they say about the bonding process is absolutely true. At any stage (or age) Permaflex/LRB will bond with itself.

If you follow the instructions this stuff will work. I speak from experience on that because the first install I did 4 years ago did not follow the instructions in one section (under the rocks on the waterfall side) and that section cracked this past winter. The rest of the pond which was clean concrete held up perfectly and looked as if it had just been painted when we drained and cleaned it.

I like the color choices too! I went with the beige. The photo shows the finished re-hab from June. The *only* part that is new Permaflex is the floor (one coat) and the back wall under the waterfall and channel. Everything else is a 4 year old installation

    Bookmark   August 21, 2014 at 10:15AM
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