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  Materials and Components
for your Pond

Part 4 in the series by Joel Police
New Haven, Indiana USA

Author’s Note: These articles are intended as general reference only. The information presented represents my perspective gained from experience as a water gardener and as a business owner. The views expressed here are also influenced by the conditions found in the Midwest and may not be as applicable in other geographic regions.

The first article of this series, Your Water Garden, provides an overview of this section. The second, Water Features, Water Gardens, and Specialized Ponds, defines the nature of these landscape elements. The third article, Planning: Location, Design, Action, focuses on the where, how and when. Here I turn to the physical building blocks that constitute the “what” of a water feature, water garden or specialized pond.

This article identifies builders’ choices for materials and components. It offers advice from my own and others’ experience with building and troubleshooting water features and water gardens. Different combinations of various materials may work for a project, but choosing the optimal blend of materials will result in the best job. Budget constraints sometimes preclude the optimal choice, so I present information for various alternative materials. In future articles I will cover pumps and filtration to give proper attention to the most vital and complex components builders face.

A wonderful aspect about water gardening is that your imagination and budget are your only limitations. You can convert virtually any item that holds water into a water feature or tub garden. Kits enable homeowners to convert almost anything into a spitting, bubbling or splashing fountain. In addition, many manufacturers market preformed plastic liners that drop into diverse pots, tubs and barrels to create instant water features.

Of course, you can stick with traditional items like a half whiskey-barrel, bathtub, sink, pottery or metal container such as a livestock tank. Each item has its own pros and cons, but nearly any item can work with a little ingenuity. Regardless of the vessel used to hold the water, the true beauty comes from what you grow in it. Before deciding what container to use, mull over a few factors.

Plastic containers or drop-in liners combine the best of safety and convenience. Modern plastics are fish-safe and stand up to the environment well. Once you find a unit that fits the shell you pick, building a water feature with a preformed unit is quick. The downside is that the manufactured dimensions limit you size wise. Plastic units require little care and often withstand winter exposure without damage from freezing. However, if the shell is susceptible to cracking or damage from ice expansion, drain and store it in the basement or garage until spring.

Pottery or concrete bowls and containers offer an array of style and color. You can easily incorporate them into existing landscape settings. Usually, the only modification required for pottery is to plug the drainage holes. Some concrete pots absorb water over time; this can stopped by painting the interior with fish-safe waterproofing paint. Depending on your climatic conditions, you may have to drain and store pottery or concrete in winter to protect it from cracking.

Metal containers such as watering cans and washtubs make great water features. Take extra care when running electrical cords over rough metal edges. The biggest concern with metal containers is rust. Most useable metal containers are tin or galvanized steel treated to make them rustproof. As with concrete containers, it may be beneficial to coat the interior of metal containers with fish-safe waterproofing paint since seams sometimes leak. Copper makes a fabulous medium to work with, due to its rust resistance and the patina it develops. Avoid copper if you want to raise fish. Copper containers and copper fountain units leach copper into the water, which can reach levels toxic to fish.

Lumber and concrete blocks give structural support for container gardens and water features using flexible liners. Select pressure-treated lumber, composites, cedar or redwood because they withstand the weather. Concrete blocks, either the grey building variety or segmented retaining wall blocks, are sturdy and weatherproof. Talk with a construction expert before choosing either wood or block.

The advantage of using wood or block combined with a flexible liner is that you can produce almost any shape and size of enclosure. Make custom-built containers part of a deck; incorporate them into an existing wall or other architectural feature. Wood usually costs more than block per unit of pond surface area. However, it does facilitate designs that are more intricate. When picking a material, consider your experience working with that material and your available tools.

Many water garden centers employ concrete blocks or wood timbers for display ponds because of their quick construction and durability. Even on larger projects, wood and blocks offer great potential. Factors such as humidity, termites and freeze/thaw cycles influence your choice; either material can perform successfully in most environments.

If your project involves a water garden or a koi pond, then choose between rigid and flexible liners. Your liner material choice affects other areas of construction. Rigid liners allow little or no flexion from water or ground pressure. At the other end of the spectrum, flexible liners move with the substrate they line. Rigid liners include plastic, fiberglass and concrete formulations while flexible liners encompass PVC (polyvinyl chloride), vinyl, EPDM (ethylene propylene diene monomer) and butyl products. A composite liner, spray-on urea liner, blends the best features of both.

Nearly everyone has seen the ubiquitous preformed pond unit. Once the mainstay of the hobby, preformed fiberglass and plastic shells come in many shapes and sizes for the homeowner to create a little oasis quickly. Marketed as easy-to-install without the hassles associated with liners (tears, punctures, roots, etc. . .), preformed units enable anyone to create a water garden in an afternoon.

When choosing a preformed unit, the tradeoff is ease of installation versus design constraints. Preformed units can be hard to disguise and naturalize, but for those not interested in an advanced setup, they are just the thing. A more thorough analysis of the pros and cons occurs in Water Features, Water Gardens & Specialized Ponds. Here I only discuss the material angle.

The biggest concern for fiberglass and plastic is temperature and frost depth. Plastic preformed units flex and deform more than fiberglass units do during freezing weather, especially where ground heave occurs. Flexing sometimes prevents damage, but in extreme conditions, cracks or creases may damage plastic and fiberglass structures. Both materials weather well over time and quite often outlast the pond itself.

Plastic and fiberglass units are fish safe. Complement them with various preformed stream and waterfall units. They readily accommodate filters, fountains and other accessories. The cost of preformed units is significantly higher than using a similar sized flexible liner, but many homeowners choose preformed ponds because they find them easier to install. Less common rigid liner structures include metal or plastic livestock tanks, children’s swimming pools and concrete structures.

By far the most complex and expensive type of rigid liner is concrete. Yet you can easily justify the expense when you consider the value of show-quality koi that thrive in properly built concrete koi ponds. Modern concrete koi ponds use fiberglass-reinforced concrete to add flexibility and tensile strength. Flexibility helps to prevent concrete from cracking.

While very similar to swimming pool construction, concrete koi ponds have some unique characteristics of their own. The plumbing and filtration systems dwarf that of a pool and water flow rates are much greater. Without the benefit of chlorine and other chemicals to combat algae, UV sterilizers and clarifiers work in conjunction with the latest bio filtering technology as opposed to sand or bead filters common in swimming pools.

Materials used for concrete construction typically entail reinforcing grid or mesh, the concrete itself and various plumbing, electrical and filtration components. Apply concrete with either a wet gun technique (Shotcrete) or a dry gun approach (Gunite). This oversimplifies the process; for most homeowners I recommend leaving the installation of concrete koi ponds to professionals.

Shotcrete and Gunite facilitate creative design opportunities. Many better-quality contractors construct realistic looking rocks and waterfalls with these systems. Natural stone is expensive; a Shotcrete or Gunite waterfall makes a cost-effective alternative to quarried stone. You can use concrete in unstable soil conditions unsuitable for liner ponds.

Concrete ponds necessitate a significant outlay, especially considering the filtration, heating and plumbing associated with state-of-the-art koi ponds. Nevertheless, this cost pays off taking into account their life span, no concerns over liner damage, superior design capabilities and the fact that most concrete pond owners also have a substantial investment in their prized koi.

As with other material types, there are always concessions to make. Besides the high initial investment, the other downside of concrete is potential for cracks. The scale and scope of concrete koi ponds also rule out most homeowners tackling the task themselves. Perhaps the biggest negative for many with concrete is not the cost, but its permanence. Typical pond owners modify their ponds approximately every five years. With concrete, once you make the pond, it is not cost effective to redo it on a regular basis.

In contrast to the permanence of concrete ponds, flexible liners take into account the ever-changing nature of water gardens. By far the most popular choice today, flexible liners give builders the option to fashion almost any shape and size of koi pond or water garden. The most significant advantage of flexible liners is their versatility. Flexible liners cannot compensate for poor planning or sloppy excavation work. However, they are excellent materials for most applications. This category of liners includes PVC, vinyl, EPDM and butyl.

The low-cost liners are PVC and vinyl compositions. Commonly used for aboveground swimming pools, these liners have been around for decades and have a loyal following among pond builders. They cost considerably less than other liner types and have a shorter life span. Vinyl and PVC liners are thinner (typically 20 mils [0.5 cm]) than EPDM and butyl (45 or 60 mils [0.11 cm or 0.15 cm]), but this makes them lighter and easier to manipulate.

Originally blue in color (from their beginning as swimming pool liners), the standard PVC and vinyl liners are usually black, but sometimes other colors, too. The knock against PVC and vinyl pertains to low puncture resistance and brittling over time. Most PVC and vinyl liners contain UV inhibitors to protect against sun damage. A bigger concern revolves around damage from rocks, roots and animal visitors.

The next step up on the liner hierarchy is EPDM liners. The majority of pond liners in the United States today are EPDM formulations. Look for 45- or 60-mil (0.11- or 0.15-cm) liners to ensure you get the benefits of using EPDM. Pond kits often include the thinner 20-mil (0.05-cm) liners prone to punctures and root penetrations. Quality varies greatly, so it pays to buy a recognized liner brand with a clearly stated warranty.  

If you follow internet discussions, you may be familiar with the debate about EPDM pond liners. The original purpose for EPDM liners was waterproofing flat roofs. Some now argue that EPDM pond liners are nothing more than the clever work of a marketing executive intent on squeezing additional money from concerned koi and goldfish owners.

Many stories, myths and misinformation exist ranging from the use of algaecides and fungicides in roofing liner to claims that all EPDM liners are of identical chemical composition. Simply put, EPDM describes a wide family of rubber products and involves a host of different formulations depending on the end use. To be safe, buy a recognized name brand, fish-safe liner even if it costs a little more than a roofing liner. Without question, many pond owners have installed roofing liner with no detrimental side effects. Nevertheless, those who do experience trouble with roofing liners bring to mind the principle of tempting fate. Naturally, the choice ultimately rests with you, the pond builder.  

Water box - Click to enlarge
Positive aspects of EPDM include a long life span, ability to withstand temperature extremes and excellent tear and puncture resistance. It is compatible with almost all types of skimmers and filters, seamable in the field (important for large projects), tolerant of heavy loads on it, and relatively easy to maneuver. Finally, good quality liners traditionally carry twenty-year or longer warranties.

While EPDM costs more than either PVC or vinyl, it is a small price to pay for the longevity and strength of the material. However, EPDM is far from foolproof. Take great care during excavation to leave no sharp stones, sticks or roots exposed that could penetrate the liner (this applies to all flexible liners). Like the less expensive liners, extended sun exposure weakens EPDM liners.

Some pond installers use this fear to justify covering every square inch of liner with stones to “protect” the liner from sun damage; this concern is unfounded. Without delving into a physics seminar on light refraction, liner exposed to sunlight is safe from UV rays except the part above the water’s surface. Exposed liner suffers from UV rays, but damage takes far more time to occur than with PVC or vinyl liner.

Butyl is a close relative of EPDM. It is a little more durable and commands a higher price tag. Like EPDM, it typically comes in 45- and 60-mil (0.11- or 0.15-cm) thicknesses and installs in the same manner. Butyl may be hard to find at a local pond dealer in the US, but it is readily available on the internet. Commonly used in Europe, butyl maintains a small but loyal following among American ponders.

In short, butyl enjoys the same advantages as EPDM and suffers from the same weaknesses, only to a lesser extent. Butyl tolerates a slightly wider range of temperature extremes and exhibits better tensile strength. For most applications, neither factor comes into play. Perhaps the most notable attributes of butyl are excellent weathering characteristics and a very long life span. Many people say that butyl is the liner of choice if you could only build one pond in a lifetime. Despite this, many opt for EPDM due to lower cost with almost identical performance, especially in the short and medium time ranges.

The newest innovation in liner technology is a urea-based spray-on liner. Just like the spray-on bed liner for trucks, spray-on pond liners are highly durable semi rigid systems. Like concrete ponds, apply spray-on liners to an excavated area and allow it to cure. This system requires stable soils -- not a good choice for sandy or loamy areas. A brush-on formula repairs concrete structures and waterproofs other rigid structures.

Literature and websites indicate that spray-on urea costs more than other flexible liners. It offers long-term durability and wonderful design capabilities. Being so new, the jury is out on its performance and durability parameters. However, it proffers great promise. I believe its popularity will increase as installation techniques improve and the price falls.

Regardless of liner selection, the first step in successful liner installation entails using an appropriate underlayment. Many do-it-yourself pond books suggest using sand, multiple layers of newspaper, carpet padding or even carpet. The top-of-the-line underlayment material is a non-woven geo-textile fabric available from water garden retailers or landscape supply companies.

While newspaper may not be your first choice, sand, carpet padding and carpet do have a place in some applications. Carpet padding or carpet functions well as underlayment over flat, hard surfaces like concrete. Carpet also works very well over rocky soils. Sand can be an effective underlayment, but suffers from the weakness that it does not work on vertical surfaces. In addition, it tends to migrate downhill on slopping surfaces.

Non-woven geo-textile underlayment is an extremely tough fabric with high tensile strength. It limits root penetration and damage from sharp rocks. Use it under the liner for external protection. Inside the pond, it affords an extra measure of protection from heavy or sharp items in the pond. Non-woven geo-textile underlayment works well for building bogs and lining marginal and lily pots to keep soil from leaching into the pond water.

Unfortunately, aggressive marketing by some “pond companies” has given fabric underlayment a bad reputation. Claims that only non-woven geo-textile fabric facilitates essential gas exchange in the soil below a pond do not help matters (sand, carpet and padding are all gas permeable). Yet the fact remains that no other underlayment combines the strength and versatility of fabric underlayment. Furthermore, it pays to read the liner warranty terms. Some suppliers require an “approved” underlayment as a condition of proper liner installation (and of honoring the liner warranty). Overall, the minimal cost of fabric underlayment is well worth the price. Combine sand, carpet, or padding with fabric to provide the utmost in liner protection.

After deciding the basic structure or “shell”, the next material to consider is tubing or pipe. Many factors influence the plumbing that circulates water. For instance, vinyl tubing’s lack of wall strength precludes its use in concrete koi ponds. The large diameter of flexible PVC rules out its use in small water features. Parameters that most affect pipe selection include wall strength (or wall thickness), pliability, and diameter.

Small water features or preformed water garden units frequently use vinyl tubing. It comes in assorted diameters and wall thicknesses, bends easily and connects with simple barb fittings and stainless hose clamps. One-inch (2.5-cm) diameter tubing typically accommodates up to approximately 1500 gallons (5700 liters) per hour. More often than not, vinyl tubing is translucent, but it also comes in black. If tubing is exposed to sunlight, use black tubing to reduce algae growth in the tubing itself.  

Lotus fountain - click to enlarge

With any vinyl tubing, select material with greater wall thickness as opposed to thin wall thicknesses. This helps prevent kinking and collapsing, the two primary downfalls of vinyl tubing. Avoid placing heavy objects on tubing and be wary of burying it in deep excavations. Despite its limitations, vinyl works well when used in situations consistent with its capabilities.

As the pump flow-rate increases, the need for larger diameter tubing arises. For diameters larger than one inch (2.5 cm), a pond builder has two basic choices -- rigid PVC pipe and flexible PVC tubing. They handle large-volume water circulation. Flexible PVC tubing uses either glued or non-glued fittings. Environmental conditions, complexity of the plumbing system, pipe lengths and budget all influence the choice of rigid or flexible PVC.

Since pipe diameter largely dictates flow rates, picking rigid or flexible PVC may not seem much of an issue. However, it becomes an issue when you insert fittings into the equation. Flexible PVC readily bends, eliminating curved fittings that rigid PVC requires. Each fitting adds to the total dynamic head, reducing the output of the pump at a given height. In addition, flexible PVC comes in lengths up to one hundred feet (30.5 meters) in the US, eliminating coupling pieces of pipe together on long runs.

Another advantage of flexible PVC comes from its elastic structure. In cold weather regions, flexible PVC withstands freezing conditions that would rupture rigid PVC. While I do not recommend allowing any piping system freeze with water in it, flexible PVC is more forgiving. It also can tolerate heavy loads placed on the pipe, so you can bury flexible PVC without worries of damage.

While ideal for many jobs, flexible PVC does cost more than rigid PVC. Flexible PVC that incorporates barbed fittings to make connections is less expensive than the glued fitting pipe. However, the downside is thinner wall thicknesses, less selection of pipe diameters and the hassle of switching between barbed hose fittings and threaded component fittings. Fittings are potential leaks if not installed correctly. Barbed fittings combined with hose clamps are far from foolproof. Finally, the curved nature of flexible PVC presents problems when making connections on short, straight pipe runs. Patience and a heat gun help, but beginners should understand some plumbing jobs might require professional help.

For many water gardens and koi ponds without complex filtration systems, flexible PVC may seem a logical choice. Nevertheless, in applications with multiple filters, bottom drains, settling chambers and manifolds to direct flow to the proper destinations, rigid PVC gains the upper hand. Plumbing a filtration system with multiple components usually involves fitting a maximum amount of equipment into minimal space. Short pipe runs, tight clearances and sharp angles necessitate exacting precision, which rigid PVC delivers. Most hardware and home centers carry a wide assortment of rigid PVC fittings and pipe diameters suitable for water gardens and koi ponds. Just like flexible PVC, working with rigid PVC requires basic plumbing knowledge and skills. Do not be afraid to seek knowledgeable help. Ready availability, ease of use and low cost all steer many beginning ponders to the rigid PVC aisle.

Rigid PVC does have limitations. Exposed piping tends to be difficult to disguise, especially around a pump or filter located within the pond. As mentioned, rigid PVC may crack or shatter under pressure of copingstones or from being buried. Ground heave presents another concern when burying rigid PVC. Most damage occurs at fittings. Finally, extreme environmental conditions such as high temperature, UV exposure or extended freezing periods may cause early failure of unprotected rigid PVC.

Despite their differences, all tubing types share some things in common. Flexible and rigid PVC use the same glued fittings while vinyl and non-glued flexible PVC use the same barbed fittings. Any system benefits from check valves, ball valves, unions and quick couplers to make maintenance and repairs simpler and to improve overall performance. Always use the largest diameter pipe the system might require, just in case you later add an upgraded pump. Lastly, research suppliers for quality, warranty, service, reputation and knowledge as well as price. Like other pond materials, pipe quality varies greatly among manufacturers.

One material often glossed over in the materials evaluation process is the stone used for coping, waterfalls and streams. Many factors influence your selection of stone. For instance, natural limestone can raise water pH and become algae-covered quickly. Sandstone breaks down and distributes fine sand sediment in the pond. This damages ball bearings in direct drive pumps. Avoid flagstone that shales heavily; it tends to crack and fracture easily, especially in sub-freezing regions.

Composition is not the only thing to contemplate when selecting stone. The shape of the stone is also instrumental in achieving the proper look and sound. For instance, using natural fieldstones or round boulders results in an entirely different looking and sounding waterfall compared to one using granite slabs. Stone size and shape also dictate some elements of pond excavation and can influence other material choices. For example, using extremely heavy stones on PVC liners or 20- mil (0.05 cm) EPDM liners may result in liner damage, even with proper construction techniques. Evaluate how well stone stacks and interlocks when building waterfalls, ledges and coping. Stone that leaves large voids and fits together poorly requires additional work and material. Properly selected stone hides the liner, creates a captivating waterfall and specifically contributes to a pleasing water feature.

After the major decisions, I turn to the finishing touches. These include fake rocks to hide hardware like filters, skimmers and electrical boxes. Many component manufacturers offer lids and other covers to hide mechanical parts of a water feature. You can readily find fake rocks or “boulders” at home stores or online. Modify fake rocks to match the color and texture of other stones you use in your water feature.

Other finishing touches include gravel or aggregate for streams, waterfalls, edging and filling in voids and spots between the stonework (no discussion about gravel on the pond bottom in this article). Choose an aggregate type in conjunction with picking a stone for coping and the waterfall so that everything matches. Nothing makes for a more unnatural water feature than using one type of stone for the coping, another for the waterfall and still another color or type of aggregate for finishing touches.

Finally, expanding foam and fish-safe silicone sealers keep the water where you want it. Avoid expanding foam designed for residential housing applications. Significant differences exist between pond foam and foam products for the house. Good quality pond foam remains flexible when cured and offers a higher level of UV protection than housing products. Foam products do not withstand long-term UV exposure. Paint any pond foam exposed to direct sunlight.

Avoid using pond foam as a “fix all” solution for poor construction work. Pond foam exists to fill voids, not to hold stone in place, fix holes or to glue the liner together. Good pond construction minimizes the use of foam and uses it only as a finishing detail, not as a component of construction.

A final material to keep on hand is fish-safe silicone to seal flanges, hardware and other fittings on skimmers and filters, depending on the type and manufacturer of the component.

Before purchasing any material, research first and buy later. Compare more than just price; in the end, quality, performance and warranty coverage are priceless. Beginning ponders often tell me about how expensive professionally built water gardens and koi ponds are. They rationalize that pond kits from big box stores are so inexpensive, they can afford to replace pumps and liners every year if they have to. Many builders fail to explain the cost of lost time and maddening frustration from repairing or rebuilding a water feature, water garden or koi pond built with cheap materials. Good materials cost more, but the compensation of enjoyment over the years more than justifies the expenditure. 

Introduction to this multi-part series
Your Water Garden

< Water Features, Water Gardens, and Specialized Ponds
< Planning: Location, Design, Action
Filtration Systems for Water Gardens and Koi Ponds >
Pumps > | Lighting >

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