We've talked a lot about liner materials, and it's pretty clear by now that the best type of pond liner is durable, strong, lightweight, and can handle exposure to the environment. At BTL Liners, we recommend the RPE options in our AquaArmor Line.
Big Rocks
When using premium liners, on rare occasions holes can happen. Aside from the usual suspects like errant animals, sharp tools, and stray rocks working up through the soil, another unexpected source of punctures or tears may be the decorative elements you use in your pond. (Remember that stunning striped boulder you saw last weekend?) The key to avoiding problems here is to place extra cushioning under the boulder but over the liner to protect against sharp edges. You can use a non-woven textile, similar to underlayment, to protect against puncture from above by limiting how much the liner can stretch under pressure. Depending on the weight of your boulder, you may also want to put additional support under the liner to avoid a similar problem as the boulder sinks into soft soil.
Once your protection is in place, use great care while moving and placing your boulder - rips and punctures can be repaired at this point, but it's not a great way to start your pond life adventure.
Floating Liners
It can be disconcerting to see your liner rising like a blister from the bottom of your pond, perhaps even carrying your river rocks with it. Stones aren't supposed to float, so what gives? Your first consideration might be whether there's a leak in the liner itself. If water soaks into the ground under your liner, it may begin to pool, especially if you have soil with high clay content. Once enough water is both underneath and over the liner, the liner will start to float.
While a leak is always a possibility, this problem is more often due to rising groundwater. Rather than water seeping out of the pond, groundwater can rise to the same level as your pond. Rising groundwater is often seen after heavy rain when the soil becomes saturated, or it could arise if a pond sits on a grade. Ponds should be placed so the ground slopes away from the pond on all sides. If heavy rain or runoff from enthusiastic watering of your prize azaleas seeps underground and moves toward your pond, the excess water may pool between the soil and liner. In a situation like this, the liner can shift and even dislodge entirely. Over time, the movement of saturated soil will erode the pond's ground support and reduce its structural integrity.
In short, floating liners are a sign of significant problems, but water table issues are challenging to fix. The best way to prevent water table problems is to do your homework from the outset and call your county extension service for information on the local water table. If you live in a rural area, well or septic tank builders may also give you helpful information. If all else fails, dig a test hole that's deeper than your pond will be and see if you get any moisture seeping in from below. The goal is to ensure your pond is located well above the existing water table; if that's impossible, consider building an above-ground pond.
Who Ordered a Bog?
Sometimes the plants and soil you place around the border of your pond create more of a natural effect than you intended. If dirt and plants cover the pond liner and reach over the pond's edge, they can absorb water directly from the pond and gradually disperse it through the surrounding soil, a process known as wicking. You may notice that your pond is perennially low on water while the pond's edges are wet and squishy. If this is the case, it's time to remove all that soil, grass, and unpotted plants as far out as the anchor trench. You can replace the greenery with stones, pebbles, or gravel. Some new plants, carefully contained in decorative pots, will soften the appearance. Anything meant to go in the ground should be planted outside the perimeter of the anchor trench.
Sagging Liners
Liners should be pulled straight (but not taut) along the sides and floor of the pond. Wrinkles and folds can cause problems when fish waste or detritus settles in those folds and can't be filtered out. Suppose a large fold keeps debris hidden at the bottom of the pond, for example. In that case, you could eventually face a situation where anaerobic bacteria takes over, and your pond starts to give off the occasional whiff of sulfur. Some less flexible liners are even prone to cracking along fold lines. Careful installation, using the highest quality liner, and ordering a custom liner to ensure a good fit will forestall most of these issues.
Over time, some liners start to stretch and sag, even if the liner was correctly installed. If it slumps along the edge of the pond, it can allow water to splash or flow behind the liner, leading to the liner floating up from the bottom and eventually eroding the supporting soil. Loss of structural integrity in this way is a recipe for disaster.
By far, the easiest way to prevent this problem from ever developing is to choose a reinforced liner. The core of RPE is a reinforcing scrim that prevents the liner from stretching and being pulled out of shape. This scrim is part of what makes the liner so durable and resistant to tearing. HDPE, EPDM, and PVC might have the word "reinforced" in their name, but reinforcement doesn't help in this case if it doesn't prevent excessive stretching and deformation.
If you have a pond that's already sagging, your best solution is to empty the pond, unanchor the liner, and pull it taut again. Make sure your anchoring system is secure and effective. You may need to re-dig your trench so that it's deep enough to hold the liner securely. If you're using stones to anchor it instead of a trench, you may need to use heavier rocks or add a second line behind the first to provide backup.
