DIY Geothermal Flush Cart

by Richard Bigge; Updated September 26, 2017

A geothermal flush cart is a pump used to circulate fluid through a loop-field system of pipes laid underground. The cart functions by filling the system with water, thereby purging, washing and pressurizing the system. To build and use the equipment, you must first understand its basic components and their function.

Items you will need

  • Flush cart installation kit
  • Instructional manual
  • 2 half-inch boiler drain valves
  • Half-inch FPT
  • 2, 1-inch male (NPT) adapters
  • U-bolts hose assembly
  • Fill & gravity drain valve
  • 2-wheel utility cart (13-inch wheels)
  • Purging system
  • 55-gallon drum
  • 2hp electric pump (45 GPM)
  • Flow center
  • Water
  • Propylene glycol
Step 1

Refer to your flush cart instructional manual to be familiar with the flush cart’s basic parts. The equipment’s basic parts include a pressure drain, electric pump, tank, two-wheeled cart, piping system, gravity drain, quick-connect couplings, switch box and filter screen. Identify all the parts as displayed in the parts list and separate them prior to beginning assembly.

Step 2

Apply thread compound to one of the half-inch boiler drain valves. Mount the boiler drain onto the half-inch FPT (female pipe thread) fitting at the base of the tank. Tighten the drain valve with slip-joint pliers. Make sure that the hose connection aims toward the front of the purging system.

Step 3

Place the base of the tank about one inch away from the back of your cart. Install the finished assembly to your two-wheeled cart using U-bolts provided with the flush cart kit.

Step 4

Apply thread sealant compound to the two one-inch male NPT adapters. Connect them to the fill and flush ports on your flow center.

Step 5

Connect hoses to adapters to the fill and flush ports of your flow center. Place your purging system one inch away from the flow center and connect hoses to supply and channel out water.

Step 6

Fill the tank on your flush cart with clean water. Set it at a position where all the hoses from the purging system will reach it. Ensure that the water levels at about three to four inches above the water and air dispersion device. Mix propylene glycol into the water at a ratio of 25 parts glycol to 75 parts water. For instance, if you have added 75 liters of water to your 100- liter tank, then you will have to add 25 liters of glycol.

Step 7

Connect the purging system to the power supply of 20 amperes and 120-volt circuit.

Step 8

Turn the valves on the flow center’s fill and flush ports to open. Do the same to the valves on the supply and outlet water lines of your purging system. Turn on the pump. Ensure that water is continually supplied to the tank of the purging system to prevent it from drying out. Do not allow the purging system to overflow.

Step 9

Wash out or purge the loop until the air stops escaping from the purging system. The level of water should not drop below one to two inches. If this occurs, it means that not all of the air has been expelled from the system.

Step 10

Shut the valve on the return hose while the purging system pump is still running, once you have finished purging the entire loop field. The pressure of the system will rise to the maximum pressure of about 20 to 25 pounds per square inch (psi). Shut the inlet valve and the pump.