General Considerations When Designing Your Pool
Shape – a simple shape is least wasteful on materials, is easier to construct, maximises water volume and surface area, and minimises creasing with a flexible liner. For informal shapes, therefore, try to stick to bold, sweeping curves.
Surface area – try to build the pool as big as possible, as appropriate for the area. A larger surface area increases the interface between the atmosphere and pool water, increasing the water ‘take-up’ of oxygen. It also increases volume, and both factors allow your pool to house a greater number of fish. Apart from special circumstances it is better to keep the length and width of the pool within reasonable proportions. Long, thin pools look odd and are not always practical for fish.
Calculating Surface Areas
Regular rectangles and squares – length x width.
Irregular shapes – here we need to either estimate the average length and width and calculate as above, or draw on some graph paper your pool shape (as close to scale as possible) and count how many whole and half squares are within the pool outline.
First example – our kidney shaped pool would have an estimated length and width of 2.75 metres x 1.25 metres which equals 3.44 sq. metres (37 sq. feet).
Second example – our tear drop shaped pool covers approximately 24 squares x (0.5 metre x 0.5 metre) equals 6 sq. metres (64.5 sq. feet).
Circular pools – 3.14 x r² i.e. 3.14 x (2x2) = 12.5 sq. metres (134.5 sq. feet).
Depth and profile – in general terms a deeper pool is preferable, both to increase water volume and to decrease total sunlight penetration (a major cause of algae). Visually try to keep the depth in proportion to the surface area and remember very deep pools may bring their own set of construction problems.
When water temperatures fall below 4°C warmer water actually sinks, and if the water is still, the fish will go down into this pocket of warmer water during the winter. An increased depth, especially with koi, and remember that only part of the pool needs to be at a good depth not necessarily all the pool. Don’t forget too, that you will lose the insulation of the earth with a rasied or partially raised pool.
Vertical sides will maximise water volume in koi pools but a 20° slope (i.e. the sides will come in 7.5cm (3 inches) for every 23 cm (9 inches) of depth) will mean that a flexible liner can be used without reinforcing the pool sides. Marginal shelves approximately 23-38cm (9-15 inch) wide need to be built into the profile, either all the way around the pond or at least where marginal pond plants are required, unless planting pockets are used as an alternative.
Pool Volume
Pool volume is as much a measure of the pool’s potential stability as the surface area, and is linked to pump and fish selection. Therefore if the surface area is limited, increasing the depth will increase this all important volume.
Calculating Pool Volume
To calculate the pool volume simply multiply the surface area of the pool by the average depth to obtain a cubic measurement. Every 1 cubic metre contains 1,000 litres (220 gallons), whilst 1 cubic foot contains 6.25 gallons (28.5 litres). Estimating average depth isn’t always easy in a pool with varying depths and sloping sides. Therefore drawing a to-scale cross section as below can be useful in aiding an estimate of the average, or will allow you to break the pool down into a number of separate layers for a more accurate calculation. Alternatively, when finally filling the pool from a hose, time how long it takes to fill a known volume (for example a 9 litre bucket) to estimate the water flow in litres per hour, and then time how long it takes to fill the pool.
Because different things matter to different people, there isn’t necessarily one best material for lining all ponds. You will need to consider cost, life expectancy, guarantee, ease and cost of installation, pool design, ease of repair and quality finish.
Flexible Pond Liners
For the vast majority of pools a flexible pond liner will usually be the best option all things considered and here is why:
• There flexibility and versatility mean that you can build a pond the shape and depth you want
• Certain pond liners are available in almost unlimited sizes
• They require little or no specialist construction knowledge. Their flexibility making them easy to handle and work with, and in the future any leaks (once found) can be easily repaired
• Although variable depending on the type of pond liner, they offer excellent guarantees and are fantastic value for money compared with other options
Black Stapelite Rubber Pond Liner
Black Stapelite Rubber Pond Liner is the best type of flexible pond liner available and has been used for decades world-wide to construct garden ponds, reservoirs, acid pits, and for flat roofing. Its 300% elasticity means that it is easier to handle and will crease less than other pond liners. We are so confident of butyl’s properties that we now offer written lifetime guarantees when you purchase a pond liner.
At 0.75 mm thick it is more resistant to tearing or puncturing than certain thinner pond liners – but it is lighter and more flexible than thicker pond liners.
Stapelite is virtually unaffected by UV rays, ozone, and oxidising agents, and remains flexible at temperatures ranging from -40°C to 120°C.
Firestone Pond Liner
Firestone Pond Liner is a high quality liner with great durability and great flexibity. It has a lifetime guarantee against any manufacturing faults (20 years only for liners with a surface area over 140 sqm). At 1mm thick the liner is extremely resistant to puncturing and tearing, but is not quite as easy to install as Stapelite.
PVC Pond Liners
If you are looking for a budget pond liner that still has good properties, then look no further than PVC. Our Heavy duty PVC Pond Liner is 0.5mm thick and has a lifetime guarantee, so for a little more money you can have an extra peace of mind.
If you're still unsure which flexible pond liner is best for you, then we will be happy to give you a small sample of each of the pond liners to test, simply email us at mailorder@stapeleywg.com
The simplest method, assuming that the pool is constructed with inward sloping sides (7.5cm (3 inches) for every 23 cm (9 inches) down), is to add twice the pools maximum depth to the pools maximum length to arrive at the pond liner length, and add twice the pools maximum depth to the maximum width to arrive at the pond liners width. The will guarantee adequate overlap.
If the pool is dug, you could also measure a cord that follows the shell of the pool along its longest length and its widest width, but remember to add at least 30cm (12 inches) to both measurements to include overlap.
For example, if the proposed pool, with sloping sides, were to measure a maximum of 2.75 metres x 1.5 meters x 0.5 meters (in any shape) the pond liner required would be 3.75 metres by 2.5 metres.
Joining Liners
Rubber liners can be joined on site, to link tow pools with a stream for example, using an adhesive and a joining tape. This method is not as effective as heat welding, so to increase the chances of success the joins should be kept as short as possible.
Pool Construction – Liner Only
1. Lay a rope or to the required shape and size of the pool. From inside the outline begin digging down to the depth of the first shelf, across the whole area of the pool. From inside the outline begin digging down to the depth of the first shelf, across the whole area of the pool – don’t forget to dig sloping sides, rather than vertical sides, if required. The pool edge can then be cut back as required for the intended edging. 
2. Once the first level has been dug, work inwards to subsequent levels, digging the whole area layer by layer. Short wooden pegs are inserted 1 metre apart around the pool and the tops levelled using a spirit level. From this you can ensure that the top edge of the pond is level, as the water will soon show up any faults. 
3. After final trimming and shaping, inspect the excavation for obvious stones etc. (see polyester matting below) and then dress the whole excavation with a 13mm (1/2 inch) layer of damp, builders sand (1 x 25 kilo bag will cover approximately 2 sq. metres (21.5 sq. feet). 
4. Fit the liner as well as possible into the excavation (leaving the liner unfolded over the pool for 20 minutes in the sun first will make the liner even more flexible), and then start to fill the pool from the tap. From the bottom, working up and around, start to ease the many minor creases into the natural corners of the pool, and form proper pleated folds. As the pool fills, the liner folds will be held in place. 
5. When the pool is full, trim the liner leaving at least 10 cm (4 inches) overlap (the exact nature of your edging), which can be held in place with 10 cm nails if required. .jpg)
6. The pool can now be edged as required. If used you may need to treat any exposed mortar with a product to neutralise the lime. You may also need to drain and refill the pool before introducing fish or plants, in case any mortar or treatment has gone into the pool.
Polyester Underlay
Whilst on good ground only a layer of sand should be required under the liner. On rough, stoney ground a polyester underlay will offer additional protection. The matting is easy to lay, being laid in strips and simply overlapped at joins. Unlike many other underlay options, matting won’t decay. If root or weed growth is apparent when digging the pool, the area can be treated with a suitable weed killer and a layer of builders grade polythene laid. Another possible precaution, especially if the ground is prone to crumbling, is to skim the shell of the excavation with a render, which will define shelves and slopes, and provide a smoother finish.
Repairing Pond Liners
In the rare event that a butyl pond liner is punchured, it ca be repaired quickly and easily with a repair kit which uses a adhesive and a repair patch (rather like a bicycle repair kit). Butyl cleaner is also recommended to ensure a good bond to the old liner. PVC and firestone liners have their own specific repair kits.
Pre-formed Ponds
These are more expensive than than equivalent sized flexible liner, however for many the ready made design and tough, crease free finish makes such pools cost effective.
Pre-formed Fiberglass Ponds
Premium range fibreglass pools are much more rigid than their plastic counterparts allowing for easier installation and minimal fuss.
How to identify leaks in your pond
1. First of all make sure its not just evaporation. In hot, dry weather and where there is good air movement, you could easily loose 3 or 4 cm of water in a week. Remember that moving water evaporates faster than still.
2. check that the loss isn’t coming from water splashing from a fountain or a waterfall, especially in windy conditions
3. check all hoses and connections for leaks, as well as filter chambers both for leaks or flooding due to blockages
4. be aware of the risk of occasional seepage or capillary action either over the edge of the liner, where the pool is edged, or at certain points along a waterfall. Problems may only occur if the pool level rises, or after the pump system is cleaned. (i.e. the pump is too powerful for the waterfall).
5. is the waterfall shell no longer level or has the waterfall shell become breached?
6. finally, if all else fails, look towards the pond liner. If water loss still occurs with all the pump systems shut down, then wait for the water loss to stop or slow down. This should give you a level to check the liner at. Be aware that the leak may still be somewhat under the settled water level, and the water loss has simply stopped due to water pressure. Check along seams and look for obvious signs of damage.
Rigid Preformed Pools
For many, preformed pools seem to offer many advantages over other options:
1. tough, rigid materials which are less prone to punchuring (however, these pools are not indestructable, especially the cheaper models or when not correctly intstalled.
2. a perfect, crease-free finish
3. easy to level with a ready finished edge
4. for some, the ‘ready designed’ aspect appeals and edging can be easier – however options are more limited.
So far so good, but there are possible drawbacks, especially over a flexible liner:
1. not as good value, volume for volume, compared with a flexible liner, which are often as little as 1/3rd of the price, with a comparable guarantee.
2. often have a pool volume due to overly fussy designs
3. usually have limited depths, rarely are they deeper than 48cm (19 inches).
4. many have poorly sized or designed marginal shelves
5. larger models could be difficult to transport and even get into the garden
As regards installation, if you can install a preformed pond correctly, then you can install a flexible liner. Ultimately there is good and bad in all, and for many the advantages outweigh the disadvantages. The key thing is to be aware of possible drawbacks and carefully select your chosen pool – remembering that the ‘enormous’ preformed shell on display in the garden centre always looks a lot smaller when installed in your garden.
Preformed pools can be made out of various qualities of stabalised plastic or fibre glass, each with their own life expectancies and guarantees. Many of the better quality plastic and fibreglass pools now have lifetime guarantees.
Installing A Rigid Preformed Pool
1. Assuming that the pool is not symmetrical (if it is, lie it face down on its rim), stand the pool face up in position. Use pegs or similar tio mark a point every 30 cm (12 inches), or as required around the pool, into the ground. Using a spade divot or sand, trace the pool outline from peg to peg. Digging 10 cm (4 inches) outside of this line excavate the whole area down to the depth of the first marginal shelf, plus 5cm (2 inches).
2. place the pool shell over4 the excavation again and mark out the next level, which is usually the base of the shell. Excavate again making the lower levels 5 cm (2 inches) wider all around and 2.5 cm (1 inch) deeper.
3. Make sure that the base of the excavation is well compacted and then line it with a 2.5cm (1 inch) layer of sand. Relocate the shell into the excavation checking all levels with a spirit level.
4. start to slowly fill the pool with then water and backfill around the pool with sand or sifted soil. Slowly as the pool fills, taking special care under the pool shelves.
Concrete Pools
These days, concrete and all that goes with it are best left to the specialits pond builder and the specialist pond, i.e. sheer sided koi pools. Construction, especially of larger pools, is not for the faint-hearted, and it can be expensive, epsecially if you have to use a builder. And whilst a well constructed pool could last 50 years plus, a poorly constructed pool may not last 5 minutes.
If the pool is to have at least 45° sloping sides, then at least a 10 cm (4 inches) followed by a 5cm (2 inches) thickness of concrete, sandwiching a reinforcing mesh, can be spread directly onto compacted earth sides and a 10-15cm (4-6 inches) hard-core base. If the pool is to have sides on or near to the vertical, then wooden shuttering would need to be used to hold the poured concrete until it sets.
The more popular option is to use hollow concrete blocks to construct the vertical walls which, especially with deeper pools, can be filled with concrete and strengthened with steel rods. Reinforcing mesh will also be added to the concrete base of deeper pools.
Once constructed, the walls of the pool can be dressed so that the construction is waterproofed, treated for lime and made decorative.
Lining options include:
1. flexible liner – all the qualities of a liner now made more suitable for deeper pools, especially with vertical sides. The liner could also be used as a ‘sandwich filling’, which is useful if liner damage id likely e.g. from animals or vandals, or a more decorative finish is required, e.g. an inner brick facing
2. fibreglass – expensive and not for the first timer, but if done properly will provide a very tough, durable finish. Especially good for informal shaped koi pools.
3. sealed render – a 1 cm (3/8 inch) thick render (which can be improved with a reinforcing fibre material mix and a waterproofing liquid) is used to dress the walls. This can then be waterproofed and treated for lime with suitable pool paint, of which there are various types and colours.
4. a decorative brick – in most situations this will quickly become tainted with algae and mulm, this this should not be a problem in a formal fountain only feature, with the use of suitable water treatments.
Despite its drawbacks concrete constructions do have their place, especially for koi pools and formal water features. Please remember that the above is only a basic introduction and that the specifics of a construction will vary from project to project; therefore get as much information as possible or contact a builder with pool construction experience, before tackling such a project.
Concrete and Mortar
Any concrete or mortar that is in direct contact with the pool water, whether used along the waterfall or directly in the pool, will need to be neutralised for free lime, which will otherwise leach into the water and could create problems for fish or plants by increasing the pH of the water. In some cases the mortar concrete will also need to be made waterproof, for example where a liner isn’t used to line the pool or waterfall.
Simple Raised Pools
Whilst not for all people and situations, raised or part raised pools have a number of plus’s:
1. they look very effective in formal situations
2. they can save a lot of digging
3. they can overcome the problems caused by a high water table and underground cables or pipework
4. the walls can provide and ideal seating area and offer a little more security with young children and animals
5. they reduce the pollution of the pond with garden debris or contamination from surface run off
6. fish and plants are closer to eye and hand – especially useful for less able bodied, the very young and koi keepers
7. the construction methods allow for the building of pools on sloping ground
Raised pools can be lined using any of the materials used in a sunken pond. There are, however, a number of important considerations: 
1. a raised pool should be approximately 15-30 cm (6-12inches) deeper than its equivalent sunken pool, as you will have lost some or all of the earth’s insulation in the winter
2. when building a partially 
raised pool, ideally have the marginal shelf at ground level to make construction easier
3. a rigid preformed pool can be constructed as a partially raised feature without a supporting brick wall. Earth can be banked and
clad with natural rock (creating a rockery) or log roll.
4. a double wall construction is always recommended especially over 30-45 cm (12-18 inches) in height, not only for stabalising but also to help construct marginal shelves or provide a wider wall for coping/seating. 
5. a concrete foundation of approxiamtely twice the wall width and 15-20 cm (6-8 inches) deep will need to be laid for the walls 
6. concrete blocks can be used for the inner wall as these are quicker and cheaper to lay.
Pool Edging
We all focus on the importance of decorative elements such as waterfalls, founatin ornaments, and plants – when it is actualy the type of edging that can really set off a pool. Whilst standard paving or crazy paving are obviuos options, especially for rigid shell pools, and can look very effective, especially with some of the new colours and styles, dare we say that at times it can also be just a little boring! You have almost as much chouce in edging as you have for amost anything else you have in your garden; therefore, use the photographs in the many good water gardens books and magazines that are available as a source of inspiration.
Consider that your pool edging may need to:
1. handle human traffic
2. allow access for wildlife
3. prevent soil or chemicals being washed into the pool
4. define the edge of the water for children
5. blend into the surrounding garden
6. provide pockets for poolside planting
7. disguise the pond lining
8. limit fishing opportunities for cats and herons
Below are some of the most popular choices:
1. standard marginal shlf plus paving edge – a 2cm (0.8inch) bed of a 3 part sand 1 part cement mortar mix should be used to bed the slabs or carzy paving, which can then be 
pointed. Over hang the edge of the paving by approximately 4 cm (1.5 inches) to hide the liner and consider a concrete collar/foundation of approximately 5-8cm (2-3 inches) thickness on poor soil or if the edging is to take frequent traffic. Also consider decorative brick, sets or pavers.
2. part submerged rock edge – bed carefully selected and placed stone onto a thick mortar mix. This provides an excellent informal finish especialy at the base of a waterfall and will hide the liner edge. A decorative paving could be used in a more formal situation, and remember to extend the shelf width if marginals are to be planted. Also consider log roll or other suitably preserved timber sleepers.
3. rugged planting pockets – as with a submerged rock edge, but the rock now holds in a soil bed. Excellent if you don’t want planting baskets and wish to provide access for wildlife. Be aware that some plants, such as many species of reeds, rushes and sedges, have sharp roots and shoots that can punchure liners, therefore either sink solid plastic tubs for these plants into the pockets or create a back rock wall and place a 2.5 cm, (1 inch) concrete bed into the bottom of the planting pocket.
4. Cobbled beach – signle or mixed size smooth pebbles or cobbles can be laid onto a mortar mix or placed directly onto the liner. The use of an underlay is recommended or the liner could be doubled up if the beach is to take human traffic – ideal for wildlife pool. Also consider decorative slabs or pavers on a slight gradient for a formal feature.
5. Lawn edge – make sure that the turf is at least 5 cm (2 inches) thick at the water’s edge to reduce drying out and if necessary dig a drainage collar to limit soil washing into the pool.
Bog Gardens
Fancy expending your horticultural horizons without a pond or wish to effectively blend your informal or wildlife pool with the rest of the garden, then look no further than a bog garden.
In simple terms this is an area, of any shape or size, that has restricted drainage. This allows for the growth of marginal plants (emergent plants that can stand waterlogging) and/or moisture-loving plants (also known as poolside plants) which prefer moist but not waterlogged soil.
Creating an isolated bog garden – loacte in a sunny or partially shaded site depending on plant specifications.
1. mark out the site as required and dig down 45 cm (18 inches) keeping good top soil but discarding poor sub soil.
2. line the excavation with a piece of builders grade polythene or PVC pond liner (only go to the cost of butyl if you are able to utilise an off cut). Pierce the liner with a garden fork at regualr interbals and then add 5 cm (2 inches) of 6-10 mm pea gravel for restrcicted drainage.
3. for ease of watering, especially with larger ares, you could snake a piece of hose pipe, punchured every few centimetres and blocked at the end, through the gravel so that a hose pipe can be connected to the buried pipe for watering in dry spells. (The buried pipe will need to be fitted with a suitable connector at the surface.)
4. refill the excavation with the top soil mix in good organic matter if necessary to improve the soil’s moisture retaining properties.
5. trim the liner and fold under 2.5 – 5cm (1-2 inches) of soil or a decorative edging, and then plant. A surface dressing or mulch could also be added for decoration, to reduce water loss and restrict weed growth.
A bog garden could also be constructed by being directly linked to the main pool.
