Elevation change required for liner seam vs. overlap.

[combatwombat]

I see it mentioned over and over in Team Aquascape videos that they are looking for at least 6" of elevation change to do a liner overlap. If it's less, they seam it.

Is this a hard and fast rule? What is the purpose of the 6" minimum? To account for potential water level changes from rainfall or debris damming a falls?

If you have a design where the lower body of water has a maximum height due to overflow, can you use an overlap instead of a seam since water level cannot rise high enough to breach the lower liner?

p.s. I am not talking about how much liner material overlaps. I know that more is always better and 1' or more will prevent wicking. I am referring specifically to vertical height of a falls.

 

[Jhn]

No idea if it’s a hard fast rule, but I’m sure it is probably to prevent wicking. Even with a larger overlap the water in between the liners will be 6” from getting out and could still wick up and over that 6” difference.

If you are unsure just seam the two liners together, while you are still in the build process.

 

[brokensword]

agree with @Jhn ; it's the distance between water sources that should be minimum of 6", and it's for anti-wicking purposes.

 

[combatwombat]

Thanks for clarifying. That makes sense.

@brokensword: If I remember right, you did a pond expansion that required seaming two HDRPE liners together, right? What method did you use to seam those liners?

I've seen some videos showing how to heat weld HDPE liners together. Looks relatively simple and I think the process is the same for HDRPE. Is that what you did?

 

[brokensword]

Thanks for clarifying. That makes sense.

@brokensword: If I remember right, you did a pond expansion that required seaming two HDRPE liners together, right? What method did you use to seam those liners?

I've seen some videos showing how to heat weld HDPE liners together. Looks relatively simple and I think the process is the same for HDRPE. Is that what you did?

nope; took out the old and put in a whole new one. Used the old (portion of) to fix bog v1's liner issues. Still, a good story of how to connect one pond next to another, all while structurely contained with mature landscape plus all the fish/frogs/turtles, in the most inconvenient way possible!