It’s best to remove old and damaged liners before adding new layers, but it is possible in some cases to just place down a new liner over the old one. You’ll need to remove everything that’s in the pond first, including any rooted plants and sand or gravel spread over the bottom. If you’re already doing all that work, you may decide to pull the old liner out too so you can add an underlayment. When leaving a liner in place, it’s also a good idea to add underlayment over the top and before a new liner. This bridges any gaps and cushions any wrinkles that formed leaks in the original liner.
Most liner materials can rest against different liners without any adverse reactions. If you used EPDM or PVC in the past and now struggle with it leaking, you can put a layer of RPE or RPP from BTL Liners right over the surface of it. However, stretching or shifting of the liner below can damage the one above it. Unless the liner is intact and you’re simply covering it to prevent the possibility of leaks due to its age, you’ll most likely want to remove any old and damaged materials before installing a new layer.
