Best way to join two pond liners

[Jim Stevenson]

Greetings. Several years ago I decided to add on to my existing pond. I dug out an adjacent hole, lined it with the same heavy rubber lining I'd used on the main pond, lowered the water level in the main and then created a connecting arm about 3 feet wide. I joined the two liners with marine cement purchased at Lowes.

That held up until iris roots grew into the seam and gradually forced the two liners apart. I've now dug out the irises and would like to reseal. Is there a better cement to use for this? I've wondered if there might be a more foamy adhesive that you could spray into the joint and that would tend to expand and better fill the clamped seam. Thanks for your time and help.

 

[Waterbug]

Clamped seam?

"Gluing" liners together normally requires both liners to be the same material. The manufacturer of the liner develops a system specifically for the task. So you'd have to know what the liners' material. I put "gluing" in quotes because the process is normally called "welding". Gluing is a little different in which any kind of goop can be used with various short term results.

All flexible liners can be joined by clamping. I don't know how you clamped these but you have to have a solid surface on both sides of the over lapped liners and then bolt together. Using any goop in this case is a bad idea imo, defeats the purpose. The goop stops everything from pushing together completely, it leaves a layer of goop. Over time that layer of goop can shrink or be moved out of the way by water, roots or bacteria.

Some liner material like EPDM is thick enough and spongy enough to act as its own gasket. So just 2 pieces of metal is needed with the 2 liners in between. For harder thinner liners you need a gasket in between each layer, so metal bar, gasket, liner 1, gasket, liner 2, gasket, metal bar. I use aluminum as the metal and stainless steel bolts. The metal should be 90 degree angle or some channel or I-beam shape. Flat bar doesn't work very well. Bolts have to be very close together, like 1-3" depending on the bar strength. Because of expensive I only do this for short applications, like a foot or two.

I normally just overlap liners so one pond is higher than the other, even if only 1". That way no seam is needed.

 

[Jim Stevenson]

Thanks. I wasn't clear. I was only referring to clamping as part of the gluing procedure, to be eventually removed. From what I've been able to glean from other posts, it seems like the Firestone tape solution is the way to go. My main concern now is that it will be hard to get the surfaces as clean as may be necessary.