How to calculate pond liner size and pump size for your water garden.

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POND CALCULATIONS

HOW TO CALCULATE LINER SIZE:
Once you have your pond size determined, you can figure out the liner size. Use the longest, widest points of your size to calculate. Use the following formula:

Length + (2 x the depth) + (2 x 1 ft overlay)=length needed
Width + (2 x the depth) + (2x1 ft overlay)=width needed

For example: a pond 10' x 6' x 3'
10+(2x3)=16+2=18 ft liner length
6+(2x3)=12+2=14 ft liner width
Means you will need a piece of liner 18x14.

HOW TO CALCULATE PUMP SIZE:
It is very important to choose the correct size of pump to get proper circulation of water. You may purchase pumps without fountain heads or pumps with fountain heads built in already. Pumps can be the most costly part of your project, so you will want to maintain it regularly and care for it properly over winter. Ideally pumps should be stored in a container of fresh water in a spot where it won't freeze, and plugged in at least once a month throughout the winter to keep it in proper working order for the next spring.

A good rule of thumb to decide on pump size is: pumps should be able to pump out close to or a little less than half the volume of the pond. So, a 350 gph pump is ideal for a 6-700 gallon pond. This is a quick method of calculating a simple pump for a pond with no waterfalls or features.

To calculate the exact pump size required for your pond, you will need first to calculate the volume of the pond, then the waterfall height (if applicable). Then you select your pump based on circulating 50% of the volume of the pond in 1 hour, at the waterfall height. The formula for volume first:

If your pond is a rectangular shape: length x width x average depth x 7.48=US gallons
If your pond is an oval shape: 1/2 diameter x 1/2 diameter x average depth x 3.14 x 7.48=US gallons

Then to calculate the waterfall height, you simply measure the height from the pump to the top of the waterfall.

For example:

160 gph pump is suitable for a waterfall with a height of 3' 3" max., which reduces the gph to 29. This doesn't leave you with much gph for pumping the volume of your pond, so you can see that a 160 gph pump is not ideal for a pond with a waterfall.

360 gph pump can pump for a waterfall height of 7'10" max., which reduces the gph to 70. At 5' gph is 120, at 3' gph is 250.

On this page, we have listed some basic sample pond supply lists for the sizes noted. Please be aware that these are approximate only, and you may or may not require everything on the list, or in the quantities mentioned.

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