Methods for installing a pond liner

My next task is planning and installing a pond liner. In fact I'll be installing multiple pond liners as I have 2 ponds and a stream to build.

I have two preformed fiberglass ponds (rigid liners) to install and for the stream I'll use a flexible liner. For further discussion on the types of liners available see cheap pond liners. Having decided upon my design and selection of materials it's time to get down to installing the pond liners.

Firstly the design 'on paper' needs to be translated to a design 'on the ground'. Because the liners will literally be at the bottom layer of the structures and levels of the water garden I'll be laying out their placement on bare earth. So the first task after clearing the area is to mark the positions of some of the major features such as the waterfall entry point, the recovery pool and the pathway that will run the full length of the garden. Now would be a good time to identify the position and space to be taken by the larger feature rocks, tree ferns and logs. I need to leave enough space for the return and overflow pipes allowing that while they'll be camouflaged they do need to be accessible.

I will use a combination of pegs, string and inverted pots as a guide to the boudaries. I considered laying a trail of sand but decided the other methods are easier to adjust if (when!) I change my mind.

I've used as a guideline that the slope of my stream should not exceed 30 - 40 degrees as the water will flow too quickly to provide any sense of depth.

Steps for installing a pond liner

1. Clear the work space leaving room for excavated dirt
2. Mark position of major features
3. Peg or otherwise mark boundaries of ponds and streams
4. Excavate hole for recovery pond (lowest part of the stream) and temporarily place the rigid liner in place. Use dirt to hold it above the pump housing (if not using an immersable pump)
5. Excavate channel for stream between top and bottom ponds
6. Check that there is sufficient fall from beginning of stream to recovery pond. If not adjust the height at one (or both)ponds accordingly and then adjust channel to match
7. Excavate intermediate ponds including the bog pond off to the side
8. If necessary adjust the depth of the recovery pond. Allow that I am going to have a 5cm layer of sand (or underlay) under the liner to protect it from stones and tree roots
9. Recheck all levels and using a garden hose run some water into the top end of each section of the stream to see if it flows according to plan. Don't run too much water so that it impedes further work for the day! Adjust as necessary.
10. For areas where I'm using flexible liner, measure the width and length for the various sections. Measuring can be done with with a flexible tape measure or a length of rope. When measuring the stream I will allow enough liner to cover the bends, curves and vertical drops. This means I'll need the width plus two times the depth and an extra 50mm for underlay (25mm each side)
11. Line all areas with sand (I'll also check out using recycled carpet underlay). The preformed rigid liners that I'm using for some sections have near-vertical sides making it difficult to use sand packing, so this would be an ideal situation for felt or rubber underlay. This underlay can be temporarily held in place by 'nailing' to the earth bank.