In an open loop system, groundwater is usually supplied to the heat pump by a drilled well with a submersible pump system. If a recharge well is to be used, it should be drilled at the same time as the primary well. The groundwater should be tested for acidity, dissolved solids and mineral content.

Wells

After a well is drilled, a drawdown test pump is used to draw water from near the bottom of the well. This test is conducted for 24 hours at twice the operating flow of the heat pump to be installed.

The test results are then interpreted to determine the expected drawdown for use in sizing the well pump. This test also serves to clear the well bore of drilling debris and residue.

In operation, the water is used on a once-through basis and then must be disposed of in some acceptable manner.

Lakes, ponds and other water sources

Since plastic pipe is buoyant even when filled, headers and service lines must be anchored in place. The loops, anchors and service lines should be assembled, leak checked and pressure tested on land.

The assembly should be filled with air, not water, and floated into place with the weights attached. When in the proper location, the system is filled with water and sunk into position.

Service lines must be buried from the structure, across the shore and out into the body of water. They may be secured to docks or piers at or near the bottom.

There have been a number of successful installations where polyethylene or polybutylene pipe coils are set in lakes or ponds.

NEVER thread a plastic fitting into a threaded copper or brass fitting if it is to be buried. This type of connection will leak over time due to wide temperature swings.