Finding the right koi pond liner is key to the success of keeping these magnificent animals.  If you plan on keeping koi or goldfish for that matter here are some things to keep in mind when deciding what liner will work best for your particular application. When building your backyard water garden pond, be sure to use our pond calculator. The calculations below explain how this is determined and how much liner you will need for your project.

Free form Pond liners

All garden pond liners are not created equal. If you use a preformed liner, then the shape and size has already been decided for you. These are like large black bathtubs to be placed in the ground. This liner would be used in a smaller space and installation is less labor intensive. This option is also the most budget friendly. If you have a small space you could also just use a small pond liner, like the options listed below.

The next three options are similar, in that they are a flexible liner that form to the shape you have created. After you have chosen your site the size of the liner must then be calculated. These types of liners will fit just about any shape.

To calculate how big of a liner you need in feet, use the formula: 2(depth)+length+3 and 2(depth)+width+3. For example, to create a water garden that is 10 feet wide by 15 feet long and 3 feet deep it would be 2(3) + 10 + 3 by 2(3) + 15 + 3. You would need 19’ x 24’ liner. The reason 3 feet is added to both length and width is to be sure there is at least a 18-inch overhang of liner per side. It’s better to have a little too much than not enough.

Here is an overview of the three kinds of flexible koi pond liners available:

PVC – polyvinyl chloride

Of the flexible liners these are the least expensive, and more puncture resistant than the EPDM liner. They can also be “welded” together to cover large areas. According to some drawbacks for this type of liner are they may contain trace amounts of arsenic, and are not safe for fish. These liners are not suitable for colder climates. Follow the links below for availability and price:

EPDM pond liners – (45 mil) ethylene propylene diene monomer

This type of liner is made from rubber. It has been the “go to” material for pond builders. This type of liner was used in the “how to build your water garden” series in the DIY section. It requires an under-layment material to protect it from direct ground contact, which could cause punctures. When purchasing this liner be sure to purchase the same size under-layment. It is U.V. stable, which means it won’t break down from the sun beating down on it. EPDM pond liners are fish and plant friendly. One drawback of this liner is its weight. It is difficult to move, and manipulate a large liner. This liner has a lifespan of approximately 20 years. However, it can far exceed that when installed properly with under-layment. Follow the links below for availability:

RPE – reinforced polyethylene

Last but certainly not least is this liner material. It is much lighter than the other two in the group. It is also puncture resistant, therefore does not require an under-layment. According to these liners will last longer than 40 years. Use the link below for availability:

Pre formed rigid pond liners

This type of liner is not recommended for koi, but its worth a mention. Unless you have one of substantial size, you will only want to keep smaller breeds of fish in these. When using a preformed liner, the shape and size has already been decided for you. These are like large black kiddie pools to be placed in the ground. They are constructed of high density polyethylene. This liner would be used in a smaller space and installation is less labor intensive. This option is also the most budget friendly. The shape of your hole must match the form of the liner for it to install properly. Use the links below for availability:

Something For Everyone

Even if you don’t desire a pond, but still want a water feature in your garden, then a pond-less waterfall may be the way to go. You will still need to calculate how large of a reservoir you will need to house your pump. Guidelines for a pond-less waterfall are as follows:

Make the reservoir three times the volume of the water in the stream and waterfall

  • Example: If your stream is 2 feet wide and 15 feet long with an average depth of 3 inches (.25feet) then:
  • 2’ width X 15’ length X .25’ depth X 7.5 (gallons per cubic foot) = 56.25gallons X 3 = 168.75 total
  • The reservoir for the above example will need to hold 168.75 gallons of water to function properly.

You achieve the same relaxing noise of rushing or trickling water without any of the maintenance that you would have with a standard pond with a waterfall. If you go this route, you will still need a pond liner of some kind. When deciding on size, be sure it goes a foot or so wider than the width of your falls in order to contain the water. It’s amazing how much water you can loose from splash over.

Final thoughts

I hope this helped you make a decision as to what koi pond liner to choose.  There is a pond or water garden for everyone. One word of advice… don’t go too small. If you go as large as you can afford or have space for you won’t be sorry. If koi are your desire then be sure to get a liner that is fish safe.

When you are ready to start your project check out our how to build a pond and the pondless waterfall diy.  You should find all the info you need here to get off to a great start and achieve professional results.

The EPDM and RPE are the two koi pond liners you should use. You are only limited by your imagination and desire. Begin your at home destination today, and enjoy the relaxing ambiance tomorrow.  Please feel free to leave a comment below.

About the author


I love being outdoors and hands on DIY. If you share my passion, you are in the right place. If I can help one person surprise themselves with the success of a project, then this website is a success.

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  1. ?? Vielen Dank und cool für die Inspirationen.! Grüße jay

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