Building a pond. Choosing the best pond liner.

Arguably the hardest part of a customer’s pond building project is to reproduce in their own back garden the pond they have in their mind’s eye – which is most likely to be based on what they have seen from Mother Nature on their travels through the countryside. Their likely aim is to install a pond that looks as though nature would have placed it there – and one that has been there for as long as anyone can remember. The scale and characteristics of their pond-to-be will determine what route they take when choosing which material to use in its construction. As their pond retailer and ‘free’ consultant, you need to recommend the best materials for the job, so they can make their dream a reality. Ponds can be made to any size or shape they desire, just like nature would have intended with all her resources to hand. With an artificial liner, they can site their pond anywhere in their garden, even above ground – to contrast what they find in nature. To achieve their goal, your customer must choose their pond building method wisely.

Some questions your pond-building customers are likely to ask:

1. Why do I need to line my pond?

All natural water bodies occur where they do because of the natural geological conditions. Pondkeepers, however, want to bring water into their own garden, where if left to nature (even over hundreds of years), would perhaps never host a pond. The underlying soil may be too permeable, or the lie of the land may not naturally collect water and they must intervene if they want a pond in their garden.

2. I have a very heavy clay soil – Can I not build my pond using this?

Clay is in fact the perfect pond building material. It’s impermeable, east to work with (but difficult to dig!!) and is actually the soil-type of choice for koi and goldfish farms. A natural mud pond provides fish with many environmental benefits which produce fish in tip-top condition. However, a clay pond will also be a very murky pond, making it less than ideal for viewing their beautiful fish. One of the benefits of choosing a liner (rather than clay) is that you can achieve crystal clear water and make a watertight pond in any soil type – whether clay, loam or sand.

3. What are my options when considering a ‘lined’ pond?

There are several routes you can take : a. an off-the-shelf instant pond approach, b. the no-holds-barred method for the more creative – a liner, or c) Concrete, a heavier, hand-made method of construction. There is obviously a market for all approaches but which is going to be the best one for your customer? Let’s look at the two most popular – preformed pools and flexible pond liners.

a. Preformed pools.
There are two or three different types of preformed pool available, offering your customer differing degrees of rigidity, lifetime expectancy and size. The most basic of preformed pools are made from a very flexible thin plastic that is moulded into various shapes, usually holding up to 70 gallons. Tougher high-density polythene pools offer improved strength and puncture resistance and although they are semi-rigid they are capable of holding nearly 200 gallons comfortably when buried. The most durable of the preformed pools are the rigid glass-fibre pools which are also the most popular. Available in a range of volumes from a tiny 30 gallons to well over 1000 gallons, these strong and durable ponds are built to last a lifetime.

If you stock a range of indoor aquaria and cabinets, you will know from your own experience that your display is limited by the space available in your store. The same will also be true for the much larger preformed ponds. It is rare for any aquatic outlet to stock the full range and you will have to choose carefully which ones to stock. It is getting rarer for customers to wait a few days while their particular choice is ordered – and in the height of the season, there may well be supply problems.

Your customer will have a good idea of the area of the garden that they want to give over to water. This will immediately allow them to focus in on the preformed ponds that are the most appropriate for their plot. The models in their size range will offer different depths, and shelving arrangements for marginal plants, some of which may be more to their liking than others.
If your customer intends their pond to be a formal, regularly shaped pond then rigid fibreglass ponds offer them many benefits in that they will not have to dig a hole to the correct geometric shape or dimensions. Just make one large enough to take a pond, back-fill accordingly and hey-presto, they’ve created a perfect formal pond without using a set square or compass. If they have chosen a pond over 300 gallons in volume it is unlikely they will be able to get it home in the boot of their car so make sure as their retailer, you can deliver it when they want it.

4. I like the idea of buying a preformed pond – how easy are they to install?

Installing a rigid pond could not be more straightforward.

1. Dig a hole a little bigger than the shape and depth of the pond.
2. Place a loose covering of moist sand in the hole.
3. Place the pond in the hole, ensuring it is level and begin filling with a hosepipe.
4. As it fills, start to backfill with loose soil or more sand, checking regularly that it is level.
5. Keep the remaining spoil to one side with a view to using it to make a raised rockery and waterfall.

NB: Warn customers when choosing a preformed pond that they should be prepared to see their pond appear to shrink as they position it in the ground. Once in-situ, a pond will often look much smaller than it did when displayed against a wall in the garden centre.
b. Flexible pond liners.
Pond liners offer your customer flexibility in both the material they use and the extent to which they can design a pond. Long gone are the days when a heavy-duty polythene sheet was the method for lining a pond. Today’s pond liners have gone the way of pond pumps in that they have been re-engineered to meet (and indeed exceed) the pond keeper’s expectations, with many pond liners now being sold with a lifetime guarantee (in excess of 25 years).

In a similar fashion to rigid ponds, flexible pond liners are available in a range of qualities that reflect their durability. Made from materials such as PVC, EPDM and butyl rubber and more recently hi-tech composite materials, which to be competitive, are guaranteed for life and as long as they’re installed correctly.
Liners are sold either pre-cut and packed or off-the-roll, depending on the size of the liner required. Ask your customer to bring their three-dimensional pond measurements so that you can then work out the area of liner they require. This is also a good opportunity to plan out a waterfall. One particular advantage a liner has over a preformed pool is that the liner can be laid to incorporate a waterfall, making the cascade in effect an integrated extension to their pond. So even if their waterfall leaks (as is often the case) as if by magic, all of the leaking water still returns to the pond. Remember to ask them if they intend to install a stone waterfall – if so, incorporate it into the liner dimensions.

Once cut off the roll, their liner should easily fit into the boot of their car (but may be deceptively heavy). Because of a liner’s flexibility, more care must be taken when preparing their excavation to protect against protruding stones or invasive roots. If the liner is going to last over 25 years, you cannot expect it to do so while pressing down hard against a sharp object.

5. What do I need to know before I can buy the correct sized liner for my pond?

Measure the dimensions of their pond (length x width x max depth) and you can then calculate the area of liner required.

For example:

To line a pond 8’ x 6’ x 3’ deep.

You will need a liner (8 + 3 + 3)’ x (6 + 3 + 3)’ in size. You then need to add at least a further 1’ to both width and length to accommodate sufficient overlap at the pond edges. So in total you would need a liner 15’ x 13’.

6. How do I lay the liner?

Prepare the shape and depth of the hole as desired (this time the customer is the designer) and then cover the surfaces with loose damp sand or even special pond underlay. I have even used old carpet very successfully (but remember to check for any old tacks!). The liner will become very supple in direct sunlight making laying it far easier. Once the liner has been laid, every attempt to reduce the number of creases should be made, pulling and stretching the liner as it fills to reduce the creases further. Only when the pond is completely full should you trim off the excess liner, leaving at least nine inches overlap. Remember to leave an extensive overlap intact to underlay their waterfall.

In summary, each method of creating a pond provides your customers with different benefits depending on the nature of their pond. Most man-made materials now offer a similar guarantee, with pond liners giving more flexibility with their pond design. Your customer digs their hole first, designing it as they go along and then chooses a liner to suit. With rigid ponds, they work the other way round, digging the hole to suit the size of the off-the-shelf pond. Flexible liners can prove difficult to install in a formal shape (square or circular) whereas preformed ponds can create that effect perfectly and immediately, also allowing a feature to be raised with minimal support. The choice is theirs but with flexible liners you’re offered far more scope as pond designer and comparatively, they offer excellent value for money. And as a stockist, the liner takes up much less room, and suits an almost infinite number of different pond shapes and sizes.

Kill blanketweed and string algae.