Joining Pond Liners Without Seaming – A Simpler Way to Expand Your Pond

The thought of needing to join two pieces of pond liner together can feel daunting. Seaming liners is a stressful process — at least, that’s been my experience!

But the good news is, in most backyard pond projects, there’s a simpler, more reliable method that avoids seams altogether.

If you’re planning to add filtration or expand your pond, this approach might save you a lot of hassle (and cash).

In this post, I’ll walk you through how I handle this challenge — and how I used this exact method in my own dream pond build.

If you prefer video content you can watch this video:

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Why You Might Need to Join Pond Liners

There are a few common reasons pond builders run into this issue:

1. You’re adding extra filtration or a stream
2. You want to expand the pond itself

If you’re in that last category, sorry mate — you’ll need a good watertight seam. But for the first option, this alternative method works great.

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A Smart Solution: Let Gravity Do the Work

A lot of pond owners come to me wanting to add filtration like a bog filter, or intake bay, or even a negative edge reservoir to an existing pond.

Bog filters and intake bays can be built inside the pond using a partition.

I usually recommend building the bog filter externally and connecting it with a stream — this keeps things simple, natural-looking, and easy to maintain.

Here’s how it works:

• Water is pumped from the pond into the bog filter.
• It flows up through layers of rock, pebbles, and plant roots.
• Then it overflows back into the pond via a stream.

Because the bog sits higher than the pond, gravity allows the water to return naturally — no fancy seaming required. You simply overlap the liners, making sure water flows in the right direction.

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How to Join Pond Liners Without Seaming

Here’s the key: water must never be able to flow uphill. If your stream liner overlaps the pond or bog liner and there’s a minimum drop of 30 cm (12″), water will always move in the right direction.

I like to:

• Overlap the liners generously
• Add a couple of beads of Firestone sealant (amazon link) as extra insurance (totally optional, but gives peace of mind)

I’ve used this method dozens of times and never had an issue.

You can repeat this same process at both ends — from the bog filter to the stream, and from the stream to the pond.

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What About Negative Edge Reservoirs?

This method also works beautifully with negative edge ponds — which are kind of like an invisible skimmer.

In this setup, the water spills over the edge of the pond into a reservoir below. The pumps live in the reservoir and send water to the bog filter, keeping your pond surface clear of debris.

And yep — it still works with liner overlaps and gravity.

If you’re planning one of these setups, make sure you understand water in motion.

I’ve included all the calculations and best practices in my blue print cheat sheet, which you can find more information on below:

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Real-World Examples from My Ponds

This isn’t just theory — I’ve used this method in some of my favourite projects:

• My dream pond features two bog filters connected with short streams.
• I also built a long stream using three separate pieces of liner, overlapping each section at the curves. That saved me a heap compared to buying one oversized piece.

With a bit of planning, you can avoid complex liner seams, reduce costs, and make your pond look more natural.

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Ready to Get Started?

If you’re expanding your pond, adding a bog filter, or connecting a stream — this overlapping liner method might be the solution you’ve been looking for.

For more step-by-step advice, check out my YouTube channel or explore more helpful articles and free resources on Ozponds.com.

And if you want a head start, don’t forget to download the Pond Formulas Cheat Sheet — it’s packed with helpful tips on sizing filters, flow rates, pump sizing, helpful videos, etc.

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