Building your own pond using a Flexible Pond Liner gives you the most freedom to decide its eventual depth, shape and contour allowing you to tailor the finished pond exactly as you want it. It is also much easier to transport home in the average family car than a rigid pre-formed shape – especially in the larger sizes. However, not all pond liners are the same – there are several different types commonly available, each with its own benefits and limitations – so it pays to pick the right one.
- Choose an open position preferably on a level site.
- DO NOT site a pond in a frost pocket or a very exposed position.
- Keep it well away from overhanging trees or it will fill up with rotting leaves in Autumn and also the underground roots could puncture the liner.
- Choose a position where the water may reflect an attractive feature like a statue or favorite plants.
- Consider a position with good access to the water and electricity supply and where the pond may be seen from the house or patio.
A common mistake is to make the pond too small. A pond 6' x 4' x 18" deep (1.8m x 1.2m x 45 cm) is the recommended minimum if you want clear water and a happy environment for plants and fish.
The most frequently seen on sale are made from polythene, PVC, EPDM or butyl and come in a variety of thicknesses, quality and price. In many ways, the choice comes down to your budget and what sort of pond you are hoping to make. While smaller ponds can successfully be lined with polythene or PVC – which are much cheaper – the liner lifespan tends to be significantly shorter, it is far more prone to tearing and cannot easily be repaired. For larger ponds – or when long-life and resistance to damage is a priority – a liner made from either butyl or EPDM is the only real choice. Although they are considerably more expensive than the alternative types, when laid in accordance with the manufacturer’s instructions, they are usually covered by a lengthy warranty period – often 30 years or more – and some brands are even guaranteed for life.
PVC offers better flexibility and durability than polythene while retaining a price advantage over butyl. Dependent on the brand, the heavy duty sheeting – typically around 0.5mm thick –often comes with a 25 year guarantee. However, if you need a liner larger than around 50 square metres, then bear in mind that the warranty drops to only 15 years for the larger sizes. While 50 square metres may sound huge, it is only enough for a circular pond around five metres across and 80cm deep – a good-sized garden pond, certainly, but hardly a boating lake!
Butyl is sometimes used as a generic catch-all description for any high quality rubber-like liner – which can obviously cause some confusion. Genuine butyl – sometimes sold as Swedish Butyl or Varnamo Trelleborg Butyl – is a natural rubber product and has a slightly textured appearance, while the synthetic EPDM – the likes of Aqualast Rubber or Firestone Liner – is smoother and feels more elastic to the touch. Making the distinction has become a little more difficult of late, since some of the latest EPDM liners have been made with an embossed surface to mimic the look of natural butyl. However, fortunately in practical terms, there is really very little to chose between them – both are truly excellent liner materials and can be repaired relatively easily. Butyl comes in two thicknesses – 0.75mm and 1mm, while EPDM tends to be available only as 1mm thick.
Properly installed, these liners are the best there is – but unsurprisingly, that sort of quality and durability does not come cheap.
Selecting the right flexible liner often becomes a bit of a “horses for courses” decision. All the commonly available materials have their uses – and their drawbacks; in the end, it really comes down to how much you want to spend and how long you want it to last. That said, whatever sort of water feature you are building, it is always wisest to buy the best quality you can, if only to safeguard your investment of time and hard work – re-lining a pond which has developed a leak and cannot be repaired is a soul-destroying task to say the least!
Quick Fit Guide To Fitting A Pond Liner
1. Use the outline of the pond marked earlier as a guide to remove any turf and all of the soil down to the first shelf level at a depth of around 23cm (9"). Level the sides sloping inwards at an angle of 200 from vertical to prevent the soil from caving in and in winter, when the pond freezes, avoid this causing damage to the liner. Calculating the size of liner. It can be very easy to underestimate the size of the liner you require and it's worthwhile outlining the shape of your pond using string, wooden pegs or a hose-pipe to enable accurate measurements to be taken. Irrespective of the pond’s shape or configuration calculating liner size follows a simple formula:
First determine the maximum length, width and depth of the pond. Then add double the depth to both the length and width measurements. This will allow for the slope of the sides and shelves and the overlap needed at the edge of the pond. Our pond, for example, measures 2.5m x 3m and 60cm deep and requires a liner 3.7m x 4.2m which translates into the nearest sheet size as 4m x 4.5m.
Note: It's well worth buying the best quality liner. Look for those with at least a 20 year guarantee.
2. Use a plank and spirit level to make sure the hole is level. Check for any stones or tree roots that could puncture the liner.
3. Mark out the position of your inner deeper section using string or wooden pegs as before and dig out the inner section making sure the bottom is level.
4. Spread a layer of damp sand approx. 5cm (2") thick over the bottom and the ledges and then cover with liner underlay.
5. Position liner evenly over the hole letting it warm in the sun briefly to make it more flexible and easy to handle and make sure the centre touches the base of the excavation.
6. Place bricks or other weights around the overlap and begin to slowly fill the pond with water. The liner will stretch and mould itself to the shape of the pond and adjust the weights if necessary as the liner settles.
Be careful when filling the pond with water, if the liner is allowed to contort and stretch too much it may puncture.
7. When the pond is full, trim off any excess liner leaving an overlap of at least 15cm (6"). This surplus can be hidden beneath rocks, turf or paving slabs bedded mortar. Paving slabs should protrude slightly to hide the liner from view.
Don't forget to leave a convenient slot between the slabs for the pump cable.