The reason we build and install a koi pond or water garden is to place a piece of nature where we want it. Chances are a pond will never develop in your backyard next to your deck.
The fact is, if you want that koi pond or water garden you’ll have to build it yourself. That’s really good news because most natural ponds are not suited to hold koi, goldfish and flowering water lilies. They’re either too deep, too shallow, too wide or too small to keep our fish and plants alive and healthy.
That’s why we build our own backyard ponds and water gardens. When we design it ourselves, we get to choose everything from where it will be positioned in our yard to how deep and wide.
Sure, you could buy a pre-formed plastic pond liner but those certainly limit your creativity and choices. Pre-formed ponds only come in small sizes and shallow depths. You’ll have to dig the hole in the exact shape and depth of the plastic shell or else the pond shell will buckle from lack of support. Pre-formed pond liners often have raised plant shelves molded into the shape of the pond.
Unfortunately, the shelves are often not wide enough to support large potted aquatic plants. With a pond liner, you can even design a beautiful stream that flows into the pond.
There is no limit to what kind of pond or water feature you can create! When you use a flexible pond liner, you get to decide where you want the raised shelves, how many and where. Flexible liners conform to the shape of the hole in the ground. You can dig any shape pond you want.
Common shapes include:
- Kidney bean shape
What to look for in a pond liner?
There are many kinds of flexible “plastic” materials but not all are suitable for lining your pond. Most plastics if used as a pond liner will degrade in a few years due to the constant exposure to sunlight, ozone, water and fluctuating temperature.
A pond liner must be resistant to UV radiation so it does not become brittle, crack and leak. The liner should also have the ability to stretch in response to temperature changes, shifting weight when you drain some water and move plants around.
Pond liner thickness is measured in “mils.” One mil equals one thousandth (0.001) of an inch.
Let’s take a look at the four most common materials used to make pond liners.
PVC (Polyvinyl Chloride) has been used for decades in aboveground swimming pools. PVC is a low-cost plastic and is used in budget pond kits. Vinyl liners are thinner (20 mils).
This makes vinyl liners lighter and easier to work with when lining the pond. The downside is PVC has a shorter lifespan compared to other types of liner materials.
If the PVC liner doesn’t have UV inhibitors, it will quickly become brittle and crack.
PVC has low puncture resistance. Abrasion and pressure caused by roots, rocks, animals, pets and working in the pond can lead to leaks.
LDPE (Low Density Polyethylene) is a common type of flexible plastic sheeting used as tarps, agriculture, construction sites and more.
It is very flexible and conforms well to the inside of a pond. It can have thickness up to about 40 mils. LDPE is not as strong or puncture resistant as other liner materials.
EPDM (Ethylene propylene diene monomer) is a synthetic rubber. There are many types of EPDM products ranging from roofing material to door seals in automobiles. EPDM manufactured specifically for ponds is completely safe for use with fish and plants.
EPDM is very tear and puncture resistant. It remains stretchy and flexible. You’ll be able to stand inside your pond without fear of damaging the liner. The rubber is ultraviolet stabilized and will resist drying out and becoming brittle.
EPDM costs more than other liner materials but the strength and durability offset the added cost. EPDM liner material is normally 45 mils thick.
The material is very heavy compared to other materials. It is more difficult to install and fold to the shape of the pond. EPDM lines can even have 20-year or longer warranties.
Don’t forget the underlayment
No matter which material you choose, be sure to use underlayment.
The first step in successful liner installation is using a good underlayment to provide a physical, protective barrier between the ground and the pond liner. Do-it-yourself pond books and websites suggest using sand, layers of newspaper, old carpet.
The best and most reliable underlayment material is a non-woven geo-textile fabric. Non-woven underlayment is an extremely tough, non-degradable material. It limits root penetration and damage from rocks. Inside the pond, it adds an extra protection when working inside the pond, visiting pets and wildlife.
Pond liner calculation
There are two ways of figuring out how much liner you’ll need.
- Dig the pond and then take measurements,
- Design the pond on paper first.
Calculating the liner’s size is easy. All you will need to do is measure the pond’s width, length and depth and then do some simple math. These calculations work in feet, yards or meters.
- Length + Depth + Depth +2 = Length of Liner
- Width + Depth + Depth + 2 = Width of Liner
These two calculations will give you the square feet/yards/meters needed to line the pond and provide enough overlap for the sides.
Top rated pond liners list
1. TotalPond EPDM Pond Liner
TotalPond is manufacturer of economical, high quality pond accessories and pumps. The liner comes in a variety of sizes (approximate):
- 10’ x 15’: (6 x 9 x 1.5-foot pond),
- 15’ x 15’: (9 x 9 x 1.5-foot pond),
- 15’ x 20’ (9 x 12 x 1.5-foot pond),
- 20’ x 20’ (12 x 10 3-foot pond).
TotalPond EPDM lines are 45-mil think for extra strength and durability. Its UV and weather resistant allowing it to withstand challenging environments. This liner is made in China and has a 20-year warranty.
2. Beckett Pond PVC Liner
Becket has been manufacturing pond liners, pumps and filters for over 15 years.
This PVC liner has a 20- mil thickness.
The low weight and economical cost make this an attractive option for new water gardeners starting out with a smaller pond.
The UV-resistant PVC has a 15-year warranty.
The 12’ x 17’ liner will make a maximum size pond of approximately 945 gallons.
3. Firestone EPDM Pond Liner
Firestone liners are considered top-of-the line. These EPDM liners have 45 mil thickness.
Their life expectancy is about 75 years. EPDM has a high flexibility even in cold weather.
Although heavier than PVC, it can be shaped to fit the contours of any pond.
Firestone liners have outstanding resistance to UV radiation, ozone and other environmental conditions.
EPDM has a high tensile strength and resists punctures. This liner has a 20-year warranty.
4. Aquascape EPDM 45 Mil Rubber Liner
Aquascape Designs is a supplier of pond supplies including water pumps, fountains, treatments and pond liners.
They offer EPDM liners in a variety of pre-cut sizes from 8’ x 10’ to 20’ x 25’.
The rubber is 45-mil thick and highly resistant to punctures.
The liner can also be used to line streams and waterfalls. The material is easy to cut and seal if you want to add a skimmer box or bottom drain.
Aquascape Designs offers a 20-year warranty on their EPDM liners.
5. Geotextile Underlayment
Don’t forget to protect your liner with underlayment. This professional geotextile is easy to use and install.
Just roll it out and cut to fit. Nonwoven geotextile fabrics are made for stabilizing soil, preventing rocks and roots from penetrating pond liner and for creating ’rock pads’ to cushion large rocks and boulders placed in the pond on top of the liner.
Just lay the pieces next to each other and install the pond liner. Use any leftover underlayment to create pads for large rocks and boulders placed inside your pond.
Any of these pond liners are suitable for creating a beautiful pond or water garden. As discussed, PVC is lightweight and easy to handle but has a shorter lifespan.
EPDM is the choice of professionals, especially for larger ponds.
If you’re creating a small water garden or pond (200-400 gallons) and have a tight budget, an economical PVC liner will get you started in the hobby.
For larger ponds, especially in locations with rock and root puncture potential, EPDM is the way to go. The extra weight and expense will be outweighed by the longer warranty and peace of mind knowing you’ve used the best pond liner available.
I have a formed pond,oblong,80’x30′[12to14 deep].Its spring fed,and “natural”,but ‘improved’by previous owner.
Would a liner be worth the [large]expence involved/.The problem I have is changes in size due to variation of input.I consitered “whack and pack” ferro-cement liner,but im thinking a rubber liner might do the trick…if 1to 2 rolls were enough.
If your pond is natural, I would not try to create an artificial liner. Just let the pond go through its natural changes.
You do realise that 45 mil (thickness) is 4.5 cm or almost 2 inches.
I think you mean 0.45 mil
Actually, it’s not that thick. Check out this mil thickness guide.
Dealing with seasonally rising water table – I have a 850 gal garden pond with what I think is a EDPM liner. After 20+ yrs it has developed a slow leak (somewhere). Planning to reline it. Sand but no underlayment when originally installed. We are at the base of a hill and, in very wet California winters, the ground water gets so high that the bottom of the pond is actually lifted and the liner billows up. I think this is unavoidable (short of installing a heavily engineered and elaborate French drain). The liner resettles pretty well, but I wonder what would happen with underlayment, if I used it…?
The pressure of the rising water table is quite powerful! In the UK some water gardeners line the bottom of the hole with clay, pounding the clay into the soil. This sometimes works to seal the hole and prevent water from lifting the liner. In your case it sounds like there is a lot of pressure from the water flowing from the hill. An underlayment probably won’t be able to divert the water away from the liner. I would seek help from a local pond center. I bet they have ideas on what works best in your situation.
Are the EPDM liners safe for turtle ponds?
Yes. EPDM liners have been used with all kinds of fish, plants and reptiles. It is completely safe for turtles.
I have an agricultural reservoir that I would like to line but it is very large – 50 feet long, 20 feet wide, and seven feet deep. It is irregular in that it has steps within it. Is there a firm that can make a custom liner for me. I am in Southern California. Thank you.
Hey Tom thank you for your question. I have sent more details to your email address.
Can you please email this entire post to me. I want to save it to a USB. Thanks,.
Hi Fran, you can save this page to your flash drive by using these simple instructions. Bob
Very informative and confirming previous research. I inherited a “pond” that was used mostly as a water-feature…no fish or turtles intended but many frogs seem to like 🙂
The pond was staggered and is about 3′ deep at the based with one step and then and edge area. The perimeter is varied, but roughly oval.
The pond liner is EPDM I think, with no geotex, and held in place with rocks that vary from river-rock to larger pieces about the size of a largish pumpkin…think slightly larger than a bowling ball. The sub-base was done with fine sand (4″) and seems unmolested with no seep or root-intrusions.
The main enemy here is deer. They actively walk in and through the pond all year. Over last winter *somebody* must have walked through and either penetrated the membrane/liner or pushed a sharp-edged rock through the same as when I filled this spring all the water drained out.
I have dug out most and soon to be all the rock, cobble, stone and muck from the existing pond with the intent of re-commissioning the pond-liner.
My question is simply: my intent is to completely replace the EPDM with the same AND add the geotex prior to the rock-bed; should I add anything else to make this a longterm solution to…anything that may trip through the pond? Absent steel-plates under the base of the liner I’m not sure what other measures I can take?
Hugh, I feel your frustration about the leak. Your plan for renovating the pond sounds like a good plan. The materials will resist puncture and pressure on the liner. Keeping deer away is an art in itself. There are all kinds of motion-sensing sprinklers and smelly sprays to repel deer. I doubt you want to fence-in the pond. Search online. Ideas range from natural repellents to planting certain aromatic plants around the pond to keep deer away.
I am in need of a small liner for my pond. The pond I have is tiny but I’d like for it to have little character. Suggestions?
I’m assuming you want a pre-formed plastic pond liner. You know, the hard, plastic type that comes in different shapes and sizes. There are so many to choose from! It really comes down to size and the look you want to go for. Keep in mind that depth matters! If the pond is really shallow and holds under about 100 gallons, it could get pretty warm in the summer months. Maybe too warm for goldfish. If your location freezes in the winter, the fish could freeze solid! But if your keeping seasonal aquatic plants there’s no need to worry about temperature. It’s common for gardeners with tiny ponds to treat their plants like annuals. Each spring they purchase a few bunches of new plants and place them in the pond.
Thank you for all the helpful info.
We are redoing our 15ftx15ft pond because the liner is leaking. We are removing the rubber liner and pouring a 2inch concrete slab. My question to you is this: after pouring the concrete, do we still need a liner on top of the concrete slab?
Hi Zak. I would use some type of padding on top of the concrete slab. You can use old carpet or soft pond underlayment material. The padding will protect the liner from long-term abrasion and accidents. I once had a stray large dog try to catch the frogs that sat on my lily leaves. That big dog would jump in and thrash around. He knocked loose rocks, plants and my pump. Use underlayment for peace of mind and long-term protection.
I have a slow leak in my liner and I am thinking about replacing the liner. I was thinking about leaving the old liner in the pond for padding and installing the new liner over it. What is your opinion on this.
Yes Frank, that is OK. Old pond liner will provide a protective cushion for the new liner.
We have a large pond that our son built using EDPM with underlay from the same supplier (of whom I have no details). Their are a few places where I need to add more EDPM and my problem is connecting two layers. Is there a glue specific to EDPM?
Hi Peter. Yes, there is. Look for a pond liner seam kit. It has everything you need to join EPDM.
Hi , I have a out of ground pond , 1.8m x 1.8m 1m , it will be sitting on a concrete base , what would be a good liner for it , I was looking at the greenseal one , any suggestions would be helpful
I would go with a material that provides a relative thick cushion to protect the liner from the abrasive surface of the concrete. Greenseal is certainly an option to consider.