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Thread: sealing rocks, waterfalls and liners

  1. #1
    Join Date
    Jun 2007
    Posts
    17

    sealing rocks, waterfalls and liners

    Believe it or not this will make my fourth pond, but I still have never built a "great" waterfall, nor have I used two liners. So I come asking for some help.

    First, I have a main-pond that is about 12' x 14' and the waterfall/stream is about 12' long with an 20' x 8' liner trying to contain an 18" waterfall/stream. My first question is where the stream meets the pond I've essentially just overlapped the long 20' liner on top of the main liner. The overlap is about down/out 4' into the main pond. But I started worrying about sort of a "siphoning" effect between the liners? The main (under) liner will be at least 4" higher than the standing water so at first I didn't think I'd have a problem, then I started getting paranoid.

    Do I need to seal this "overlap"????

    Second as I build the waterfall stream I've read about using dirt/sand to minimize the "gaps" under/around the rocks. I'm assuming the liner goes over the sand and then the rock. But I still need to seal up the waterfall spillway and the "top rock".....I'd like to use black silicone sealant vs. foam...I've found it to be a lot cheaper than foam.

    What is the best sealant these days???? I'm in Michigan it will freeze....

    I'll try to get some pics up when I get home...

  2. #2
    Join Date
    Mar 2007
    Posts
    1,127
    Ideally you should have an 8'' overlap with the liners to avoid capillary action.........They shouldn't need to be sealed with this overlap. Needless to say there ahs t0 be some vertical rise here.

    When building the stream and falls it'll be a lot easier to use foam than the silicone. Use small rocks to fill large voids and then fill with foam. You want the water staying on top of all the rock and spill rocks. The foam fills all these nooks and crannies very well.

    While the black foam is very nice and very easy to hide, the other colours are about half the price, work every bit as well...check those out.

    Here's a pic of my simple falls just after it was built...I used yellow foam to seal it

  3. #3
    Join Date
    Jun 2007
    Posts
    17
    Quote Originally Posted by Graham 83 View Post
    While the black foam is very nice and very easy to hide, the other colours are about half the price, work every bit as well...check those out.
    Where do I find the "other colors" do you mean like "Great Stuff" foam insulation material?

  4. #4
    Join Date
    Mar 2007
    Posts
    1,127
    Any expanding foam insulation is fine....none of them are UV protected so anything exposed will break down over time.

    Give it 24 hours to set and then cut away any area that show or hide with additional rock.

    I help a neighbor build this one last spring...about 22' long with an 8' rise...we used about 8 cans of the yellow stuff




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