Building a Pond
Basic steps and guidelines to digging a backyard pond and watergarden.
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A natural pond can be a thing of beauty, full of fish and surrounded by turtles and frogs, covered with delicate aquatic flowers and plants. Building a pond is not as difficult as you may think and there are a few step-by-step instructions to follow if you want to build a pond. You don't need a lot of space to have a backyard pond in fact many people are able to create interesting water features in very small spaces and thanks to the new supply of inexpensive pond skimmers, filters and more efficient pumps and water conditioners it has made owning a pond easier than ever.

Rural dwellers may have the advantage because their property size is often larger and a pond can take on large dimensions sometimes becoming larger than one acre if the clay soil is ideal for water retention. There is no real limit to the size of pond that you can build but if you're like us it is often based on a budget. Often ask me how much does it cost to build a pond and there is no real answer.


A large pond from one quarter acre to three acres for example, that requires mechanical shovels to build the dam and place large boulders for landscaping around the pond will typically cost in the range of $0.75 to $1.50 per square foot. This will depend on the contractor you choose and the end result you wish: a natural or swimming pond that has shorelines and rock features to look like a natural lake, if done properly, will cost more than if you open the yellow pages and choose an excavator who can dig you a basic hole.

There is no right and wrong way but most of our clients do the work themselves so we will concentrate more on building a small backyard pond. Most of us know someone who has gone through the experience of installing one and there are a few rules to follow if you want to have a successful project that will be self-sustaining and won't cost a fortune. We'll assume that most people will be using a pond liner for their pond as most of the properties in cities and towns is too porous to support an unlined pond. We've seen people who have dug a large, lovely shaped hole, in their backyard and gone through enormous work and money to build a pond but then found that it didn't hold water and they were then forced to re-start from scratch and install the liner.

Pond Liners & Membranes
So we'll assume that you will be requiring a pond liner which is also called a membrane. Smaller basins and backyard ponds only require a lightweight material. We use a PVC, polyvinyl chlorine, membrane that will resist frost and ultra-violet light. Sunlight will damage cheap materials so it is best to ensure your membrane has this protective feature, most do but you should ask your supplier. Most 20 mil membrane should cost around $1 per square foot and can be bought in standard sized rolls or get a custom size piece cut at your local garden supply store as most such retailers carry this and the 35 mil liner that is slightly thicker and can buy for $1.50 per foot. The 20 mil and 35 mil materials should come with a 20 year warranty if you place a geo-textile protective barrier under and on top of the liner. There is a 45 mil EPDM, ethylene-propylene-diene-terpolymer, heavy -duty membrane that is available and we often use this strong and puncture resistant material for waterfalls and streams between two basins. It can cost from $0.80 - $1.50 per square foot. Using a thicker material will reduce the risk of a breech or puncture which could result in you're fixing a leaky pond. Luckily, these membranes can be repaired and sealing foam is available to help with sealing a pond.

But before you buy pond liner and before you break the soil you should draw the pond outline on your property. We use a rubber garden hose to experiment with different shapes. By pounding in wooden pickets or wooden pegs in various places you can create bends and angles in the garden hose so you're pond design can be given a more fluid look. Keep in mind that the winning pond design is often the simplest shape you would imagine. Think about how nature works in the natural settings of the wilderness…small, often circular craters, when reflecting the leaves and blue sky, can be the most memorable little ponds you'll see!

Take a look at the initial garden hose shape from many angles and don't forget to go inside the house and look through the windows that open towards the pond and see how the shape looks. Go to the upstairs rooms as well as this is a critical step to help you see if your chosen shape and position in the yard is giving proper sightlines. Make sure your design will blend with the rest of your backyard or an adjacent garden. Of course it is mainly common sense but the key is to take time for the planning because once you start with the shovels it is harder to change directions!

Calculating the pond liner size Many beginners take measurements from their outline and do some rough calculations and then scurry off to the pond supply store with such enthusiasm only to come home with a specially-cut length of material to find that it is too small.

There is a simple formula to help calculate the dimensions of the pond liner you'll need. Buy our highest rated pond liners

Width - The formula to determine the width of your membrane is 2 x pond depth + pond width + 2 feet = required width.
Length - The formula to determine the length of your membrane is 2 x pond depth + pond length + 2 feet = required length. .

Digging a Pond
Once the preparations have been done and your basic supplies are sitting beside the back door and you've assembled your family and best friends it's time to start doing the hard work. Take your time so you don't hurt your back if you are using old fashioned elbow grease and be slow on the accelerator if you are using a small back-hoe. The wheels of the back-hoe can tear up a nice lawn so make sure the ground is dry and you do as little turning on a dime as possible! We've seen some lovely yards end up looking like a monster truck track after an overzealous backhoe operator was a little too hard on the diesel pedal!

Cut your sod or turf and carefully place it in the shade in case you need to re-sod any areas around the edge of the pond for the finishing touches. Start by digging down to the depth you want and remember to use an approximate 20 degree angle to the inner walls of your pond. The slope of a natural pond tends to want to adhere to a 2:1 slope but in your own construction think of 20 degrees as the ideal slope. It is a very good idea to make steps from 6 to 12 inches wide at 8 inch depth variations to accommodate your aquatic plants and provide a solid step for any rock features you will add later. Always dig everything 2 inches deeper and wider than you want it to be to allow for the sand backfill and the liners and geo textiles which will be added.

Leveling the pond at this early stage is critical and the fastest way to verify a centering of your pond is to place a 2 x 4 on its edge across the length and width and to place a carpenter's level on it. Adjust the sides as necessary until the bubble is centered; this step is important because if the sides are not equal then you risk having the liner not fit!

Once the excavation has been done lay a nice layer of sand in the entire pond and then you can stretch your geo-textile and liner over the pond making sure it is fairly snug against the steps you've formed. You don't want to have the material stretching over corners so take the time to slide everything into position with your fingers or use a rubber mallet to carefully make everything flat. Place large stones or cement pavers on the outside leading edge of the liner so it stays in place and you can at this point turn on the garden hose and start filling the pond.

Installing a moulded or preformed pond
Most pond stores can sell you a high density textured polyresin moulded pond with rigid side , flat bottoms and planting areas. These inexpensive pre-formed ponds come in sizes from 100 gallons to 220 gallons and even larger and when you buy one you can expect to pay between a price of $150 and $300. They come in a variety of shapes and some include a spillway built in to have two or more placed together in an archipelago! Incredible things can be done with these systems so use your imagination especially when it comes to the water courses and plants you install once it's finished.

Place the moulded pond in your yard, again looking at it from the house, and other angles to help imagine how the completed project will look. Mark the final position on the lawn by pounding wooden pegs every 8 inches around the plastic pond, then dig a hole slightly larger (don't forget to keep the turf you've removed in the shade and moist) and ensure the lip of the pond is a few inches above the grass level. Use the 2 x 4 and the carpenter's level to make sure it's level. Always compact the earth beneath the pond before laying it; we like to put a thin layer of sand in the hole first so we can adjust the level of the pond afterwards. The edge of your molded pond should rise two inches above the surrounding ground.

Waterfalls & Water Courses

Before we discuss the plantation of your pond lets talk a bit about choosing a pump first for the circulation and waterfeatures you will add. If you are planning on having a waterfall you should take heed of the following way to calculate the pump for a waterfall flow: 100 gallons of water per hour for every inch of waterfall width.

So if your water fall is two feet wide that is 24 inches which means you will require a submersible pump that delivers 2400 gallons per hour, don't forget to look carefully at the flow specifications of the pump as you need to consider the head or height of your water flow. The difference in height from the top of your waterfall to the depth of your pump can significantly influence the total number of gallons per hour; we find it better to have a slightly larger flow as opposed to less flow because it's easier to bleed off any excess flow or insert a control valve or ball valve if we need to but it's harder to try and squeeze a little more flow from an undersized pump.

You can build a catchments pond at the highest point to create a waterfall that flows naturally, or you can have the outlet of the pump be the source of the waterfall. We've seen it done both ways but one benefit of filling a pool at the top of the waterfall is that the water tends to look a little more natural as it flows down the stream or over the race way. Things to remember: keep your pump in a screened filter box or a filter bag to prevent sediments and debris from clogging the intake. You will incur some friction loss for every 10 linear feet of tubing especially in smaller diameter pipes like 1 or 2 inch pipes, it's about 1 foot of friction loss or head loss for every ten feet (these inches will directly affect the head capacity of your pump).

An example: To have a waterfall that is 18 inches wide and 3 feet high which has 20 feet of tubing between the pump and the top of the waterfall requires a pump that has the capacity to provide 1800 gallons per hour at 5 feet. Check the specs carefully and do the math properly so there won't be any surprises.

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Best Plants for a Small Pond
The water needs to be stabilized before you can safely introduce any sort of life into your pond. Most people will use water directly from the town or city supply which may be chlorinated so it's good to allow the water to gas-off before you place your plants or add fish another reason to allow the water to sit for a while is to allow the temperature to adjust to the ambient atmospheric values. Pond conditioners are available to combat the harmful effects of chlorine, acid rains or chloramines and should be added properly following directions before you plant.

Using planting baskets makes the most sense for backyard ponds because we don't usually have soil planting beds in such small backyard ponds. The planting basket allows small quantities of soil to be used without the risk of causing murky water or have the soil get disturbed by fish or circulation and just end up as muck on the bottom. There is special pond soils that is formulated for use with baskets and aquatic plants and your retailer should carry this; regular dirt isn't recommended. Once you have finished planting according to the instructions specific for each species you cover the soil in the baskets with a layer of stones; this keeps the fish from eating the roots of the plants or from pulling out the roots and causing the soil to mix with the water.

Nympheas, shallow water species and bog plants as well as oxygenating plants are a good well-rounded approach; add a few of each plant and you'll see a healthy and vibrant ecosystem! Ensure the rhizome of your Nympheas are placed at a 45 degree angle in the soil, this helps them really flourish, and it is a good idea to add a pellet of plant food into the basket on planting! Nympheas can be placed in waters from 6 inches deep to up to 26 inches although it's probably best to plant them closer to the surface if they haven't fully developed as the season can be short and you want to enjoy the flowers! The shallow water and bog species are planted at water level or to a depth of around 12 inches depending on your chosen plants. Oxygenating plants help provide your fish with beneficial oxygen and are typically below the surface planted in baskets on steps that are from 8 to 36 inches deep. Make sure you get a plant that is not invasive or you will have a problem!

Maintaining Water Levels
Any pond will lose water due to evaporation especially on hot days or if you have a splashing fountain or a waterfall as the droplets turn to mist they are evaporated. Hot direct sun will cause the water level to drop and this can be harmful for the plants or koi or goldfish. Using a float valve is the simplest way to keep the level of your pond constant. The small float ball on the end of a brass arm, similar to what's in the back of most toilet bowls, will turn on a small valve whenever the level drops below your required level, these simple floater systems are fully adjustable and an easy to install 4 inch perforated pipe or "French Drain" as it is sometimes called helps ensure the level never overflows! All of these little devices can be hidden under stone or behind little garden frogs and gnomes so they keep out of sight and do their job!

Small Pond & Water Garden Aeration Buy our highest rated pond liners
Email us for information or with your pond building questions. There is no charge for our pond services.
Please note that all emails or questions submitted to The Pond Report become the property of The Pond Report and may be re-printed.
Your name will not be used if we re-print your question. Submitting a question does not guarantee a response.

Small Pond Aeration A small backyard fish pond needs aeration not only for the increased levels of life supporting oxygen but also to help keep the water circulating and reduce gases and energizing beneficial microbes in the water column. Nitrifying bacteria really needs a high oxygen level to be efficient. A cheap aerator is easy to buy and they are of very good quality these days; a $200 aerator will cost only pennies per day to operate and will make a huge difference in the quality of the pond.

Make sure your air pump is placed in an area that is higher than the water level to prevent the rare but problematic condition of having water backflow due to gravity down the airline to the compressor. Small air stones in the bottom of the pond are best for aeration and they can be placed in small baskets on the bottom, usually weighted with stones on top of the diffuser to allow the small bubbles to rise.

To determine the correct size of aerator compressor you need to know the volume of water. Many pumps these days give their output in liters per minute. Small units can provide 15 liters per minute while larger one can deliver over 80 liters per minute even up to 300 liters per minute. You want to calculate the volume in liters to determine the correct size aerator as they are mostly listed in the flow in liters so this is your pond size calculator to calculate pond volume in liters use the formula:

Length (feet) x width (feet) x depth (feet) x 28.3 = The number of liters in a pond.

If your pond has a volume of:
- 7, 000 to 14,000 liters use a 15 lpm (liters per minute) air pump with 2 - 4 diffuser airstones.
- 14, 000 to 70,500 liters use a 48 lpm air pump with 3 - 6 diffuser air stones.
- 70, 500 to 175,000 liters use a 68 lpm air pump with 4 - 8 diffuser airstones.
- 175, 000 to 282,500 liters use a 81 lpm air pump with 6 - 10 diffuser air stones.

Many people use the standard formula of gallons for volume as well as cfm (cubic feet per minute) instead of the metric version so we have converted the liters to gallons and done the converting liters per minute into cubic feet per minute for you:

If your pond has a volume of:
- 1,850 to 3,700 gallons use a 0.5 cfm (cubic feet per minute) air pump with 2 - 4 diffuser airstones.
- 3,700 to 18,600 gallons use a 1.6 cfm air pump with 3 - 6 diffuser air stones.
- 18,600 to 46,230 gallons use a 2.3 cfm air pump with 4 - 8 diffuser airstones.
- 46,230 to 74,625 gallons use a 2.8 cfm air pump with 6 - 10 diffuser air stones.

These are only average recommendations. Consult with us to be sure you are adding the correct system.

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Pond Building Website & Ebooks

Our Best Pond Plans & Pond Building Books & Guides

Here are some websites we recommend if you are looking for simple instructions for free.
Building a Garden Pond
http://www.erodent.co.uk/GardenPond/
Watch the progress of our new wildlife pond over the year.
A simple step by step guide with pictures and updates on the wildlife of the pond.

Photo Essay: Water Garden Installation
http://clearwaterlandscapes.com/pondphotos.htm
The following gives an overview of the installation of their first pond and waterfalls. Each site will be unique and require site specific techniques, but this page will illustrate that having a beautiful, satisfying water garden is certainly in the realm of possibility for the do it yourself homeowner. A modest investment (about half the cost of a hot tub) and some vigorous aerobic exercise are all that's required to enjoy your own backyard oasis. (To see their step-by-step installation of our most recent pond, you can download their free ebook)

Certified AquaScape Contractors
http://www.certifiedaquascapecontractor.com/pond-construction.php
Excellant resource that includes their 18 Steps of Pond Construction from Start to Finish: 1. Mark Pond Area 2. Place Skimmer and Waterfalls 3. Lay Plumbing 4. Hook up waterfalls 5.Excavate Pond 6. Install Liner and Underlayment 7. Hook-up Skimmer 8. Rock in Pond 9.Position Underwater Lights 10.Wash Stones 11.Fill Pond 12.Build Waterfall and Stream 13.Bring in Top Soil 14.Build Retaining Wall 15.Tweak Waterfall 16.Trim Liner 17.Mulch Berm 18.Clean Up . Of course they may have forgot my favorite step which is 19 and 20 to have a beer and watch my pond!!

Certified Aquascape Contractors (CAC's) are the most qualified and informed installers in the pond construction industry. All CAC's are required to attend continual training and education seminars and maintain a proven record of outstanding work and dedicated customer service and support.

The pond report also has information on:
pond aeration systems | a pond and the seasons | pond algae control | solar aeration systems | windmill aeration systems | deicers & bubblers | get links to your website | pond questions from our readers | pond links & resources | eurasian milfoil | pond dyes and colorants | pond pumps & waterfall pumps |

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