This simple guide gives you all you need to know to install a pond liner in easy to follow steps.
If you have not chosen your pond liner yet, we recommend reading out our pond liner guide to help you select the right size and type of liner for your pond.
Before you begin digging it is important to mark out the shape of your pond. A good way to do this is with a length of rope or hosepipe. Square and rectangular shapes are ideal for formal ponds, and gentle curves tend to work better for more natural looking ponds. Avoid making narrow areas or tight corners, as these tend to accummulate waste and restrict the flow of oxygenated water.
Depending on the size of your pond and the type of soil you have, you will need to decide whether to dig your pond out by hand or use a digger. A spade and fork are the best choice of tools for digging by hand, and are great for precise work. However you may want to rent an excavator for a day and perhaps someone to operate it for you.
It is important to get the right depth for your pond. Deeper ponds tend to be healthier and have more stable temperatures. This is turn means less chance of seasonal algal blooms as the water warms up.
Natural ponds should be at least 0.6 metres, goldfish ponds should be at least 1m deep, and koi ponds should be a minimum of 1.3m deep (but ideally at least 1.5m deep) .
It is a good idea to create marginal shelves around the edges of your pond for plants. These should be 30-40cm below the water line, and about the same in width to accommodate planting baskets. Use a spirit level to ensure your shelves are level so that planting baskets wont fall off.
Having dug out your pond, the next step is to remove any stones and plant roots that might puncture your pond liner. If you have flinty soil or are near trees with protruding roots then extra care will be needed to clear the area ready for installation.
It is a good idea to lay beds of sand roughly 75-100mm thick on the pond base and shelves of your pond. This gives added protection from potential punctures. Building sand is easy to find in large DIY stores or builders merchants and comes in handy 25kg bags. If you have a large pond you may instead find it easier (and cheaper) to get some large bags of sand delivered.
With your pond carefully prepared, you can now lay your pond liner underlay. Underlay comes in sheets and rolls which must be rolled out to cover the entire surface of your pond. Make sure if fits snuggly around all the contours and into corners.
Underlay can be cut with a sharp knife or scissors to help remove creases. They can also be cut down to fit various areas of your pond. The sheets must overlap one another to ensure a continuous layer of protection for your pond liner.
You are now ready to lay your pond liner. It is a good idea for two or more people to lay out your pond liner depending on the size as it makes the job easier.
It is extremely important not to tread on the liner unless with soft soled shoes. Also avoid taking any sharp tools or objects into the pond that could accidentally puncture it.
Begin by carefullly rolling out or lifting your liner into position. Gently push the liner into all the countours of your pond, and weigh it down with smooth stones or bricks on the base, shelves and also around the top lip of your pond. Take care to ensure than the liner is central, and folds over the top lip of your pond comfortably all the way around.
To accommodate corners and contours you will need to fold the liner in various places. Use as few folds as possible and try to make them as neat as you can. Use smooth stones or brick to hold your folds in place.
You now need to gradually add water to your pond. As you do so, the liner will pin itself to the base and walls of your pond. This gives you the opportunity to adjust and neaten folds and creases.
If you find the liner is being stretched too tightly, loosen the liner above to provide some slack. What you are aiming for are nice smooth areas with neat folds, without stretching the liner.
It is a good idea to tackle one level of the pond at a time, neatening the liner as you go. Beginning with the base, you can work your way upwards to any shelves or ledges, and finally to the top lip of your pond.
Your pond should now be full of water and the liner flapped over edges of your pond. You can now adjust and add more weights around the lip to gently hold the liner in position. You want to stop it flopping back into your pond but at the same time allow for a little movement.
You should now leave your pond for 24 hours so that the liner can settle into position. If any stretched areas have appeared after this time it is important to release extra slack to remove them before progressing.
Now that your pond liner has had a chance to settle, you may need to loosen off any areas around the top lip that are being stretched. You can also smooth out any creases that have appeared and tidy up your folds.
Having done this you can trim off any excess liner, leaving at least 30cm overlap over the top lip all the way around.
Top tip: It is a good idea to retain any off cuts. These can be cut down to provide additional protective mats upon which planting baskets, pond equipment, or a plinth for a fountain can be placed. This gives a little extra protection for your liner.
With your liner now in position and bedded in, you are ready to edge your pond. There are a variety of materials you can use from man-made bricks and paving stones, to natural rock such as limestone or sandstone.
Whatever material you use, it is a good idea to lay these on a bed of stong concrete mortar. We recommend a sharp sand mix (coarse sand) rather than building sand for added strength and a 3:1 sand to cement ratio.
If you are using flat materials such as bricks or paving stones it is a good idea to maintain a constant level around the edge of your pond. A neat line should also be maintained nearest the water edge, even if your edging material is irregular in shape. It may be worth using a landscaper or builder to do this for you for a really professional finish.
Natural stone can take on a more irregular appearance, but still be sure to fit the pieces together in such a way that the mortar holds them securely in position. Otherwise you risk the edging breaking up over time and becoming unsafe.
If you are looking to have a filter system, it is a good idea to run any suction hoses over the lip of the pond but under the edging material in order to hide it.
Once the edging is done, leave it for a few days to ‘go off’ before walking upon it. The concrete mortar may look dry after only a few hours but it takes time for the chemical reaction to occur so that it hardens. You will see the mortar colour change from green to a pale colour as it goes off.
With your pond completed you are now ready to introduce your pond equipment. If you have fish then a filter system and pump are generally a very good idea. You may also want a fountain that not only looks great but helps oxygenate the water. These can be standalone water features with dedicated pumps or ‘plug in and play’ fountain pumps.