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.