Materials and Components
for your Pond
Part 4 in the series by Joel Police
New Haven, Indiana USA
Authors 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
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
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
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
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
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, childrens
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
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
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 waters 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 tubings
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
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
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
Your Water Garden
< Water Features,
Water Gardens, and Specialized Ponds
< Planning: Location,
Filtration Systems for Water Gardens
and Koi Ponds >
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