How to Test Your Soil


The soil conditions for your lot must be figured out by digging test holes where the earth loop will be installed. There is no other way to figure it out. Every horizontal loop installation must have soil samples taken or we will only be guessing what size earth loop to design. Most geothermal heat pump contractors guess, and that is one of the reasons that there is so much trouble in the industry. Since geothermal heat pumps are installed for energy (and money) saving, there cannot be any guessing about sizing and designing any part of it.

Most people these days have a video camera, so you can easily make a video while you are doing a soils test and email the video to us. People send information of their soil testing, their furnace rooms, the areas where the air ducting will be installed, their windows, and many other details of their home so we can correctly calculate their geothermal system for them.

The Test

Before you do any digging or testing, be sure that it has not rained for at least 24 hours, because sometimes surface water will run into the hole and then the testing results will be inaccurate.

Your earth loop designer will tell you how deep to dig your test holes. You should be able to reach a depth of about 4 or 5 feet with a pair of post-hole diggers, but if you must test deeper than this, you'll need an excavator to dig the holes for you.

You will need to dig at least 2 test holes: one in your front yard and one in your back yard. You may need to dig more if your earth loop designer requires it. You must do the test as soon as the dirt is removed from the trench, or as soon as you dig your last shovel of soil out of the hole. If you have an excavator dig for you, have them dig down to the specified depth, and then have them bring up a scoop of dirt for you to test. NEVER GET DOWN INTO AN EXCAVATED TRENCH THAT IS MORE THAN 4-FEET DEEP BECAUSE IT MAY CAVE IN ON YOU AND KILL YOU.

Have someone take a video of you doing all the tests. Be sure to say where the test hole was dug as you start the test (as in front yard, back yard, side yard, top of the hill, bottom of the hill, etc.).

Dig down to your required depth, and immediately bring up a shovel of soil. Take a handful of soil and close your fist on it tight. Then open your fist so I can see if the soil packs in your hand. Next take a pen or something like it and see how far the pen will push into the soil before it falls apart. Do this test 3 times in a row, pulling a new sample of soil out of the hole for each test.

The purpose of the last test is to tell us how much water is in the soil. Wait 1 hour and look into the hole. If you look into the hole after an hour and see any water standing in it, it means the soil is saturated with water, and that is the best we can hope for. You won't have to bring any more soil out of the hole; just tell us where the hole is and that you saw water in it. If you don't see any water in the hole, bring another scoop of soil out and do one more test in the same way you did the other tests, videoing it also.

Or you can send us the soil samples

If you don't have a video camera, or you'd rather not do the tests yourself, you can send your soil samples to us and we will analyze them. Dig the test holes in your front and back yard, and have freezer bags ready. Once you are at the 4-foot depth take about 2 cups of soil and put it into a freezer bag, and triple bag it. Try to push out as much air as you can. Mark the bags "First Test Sample" and whether it's from the front or back yard (or wherever it's from).

Wait 1 hour and see if there is any water in the holes, because if you have saturated soil, we won't need the soil sent to us. If you don't see water, then take another soil sample from each hole, and put them into separate triple-bagged freezer bags. Mark them "Sample taken after one hour" and where it's from. Put all the freezer bags into a box and contact us for our shipping address.