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Commercial Flush Cart
To flush debris and purge air from a piping system containing water requires a minimum flow velocity of two feet per second. In a well designed residential system or a small commercial system of up to six tons, this can be accomplished with a fairly small, high pressure pump of 1.5-2.0 hp through the valves on the pump modules supplied by heat pump manufacturers.
Larger commercial systems require planning and larger pumps. A 200-ton earth loop can contain 2,500 to 3,500 US gallons (9,500 - 13,300 litres) of fluid, not including the fluid in piping inside the building. A geothermal ice rink system, with the earth loop, the rink floor and the building system can easily hold 8-12,000 US gallons (30-45,000 litres).
Besides the sheer volume of fluid, the size of the pipe in the system must be taken into account when determining the flow rate of the pump needed to flush the system. The following chart shows the flow needed to achieve a velocity of two feet per second for several pipe sizes.
Volume & Flushing Velocities of HDPE pipe
| Pipe Size |
I.D.(inches) |
Volume
USgal/ft |
Flow
for 2 FPS
USgal/min |
Volume
l/metre |
Flow
for 0.60 metres/sec |
| 0.75" SDR11 |
0.851 |
0.030 |
3.6 |
0.37 |
0.23 |
| 1.00" SDR11 |
1.066 |
0.046 |
5.6 |
0.58 |
0.35 |
| 1.25" SDR11 |
1.346 |
0.074 |
8.9 |
0.92 |
0.56 |
| 1.25" SDR13.5 |
1.404 |
0.080 |
9.7 |
1.00 |
0.61 |
| 1.50" SDR11 |
1.541 |
0.097 |
11.7 |
1.20 |
0.73 |
| 1.50" SDR13.5 |
1.607 |
0.105 |
12.7 |
1.31 |
0.80 |
| 2.00" SDR11 |
1.926 |
0.151 |
18.2 |
1.89 |
1.15 |
| 2.00" SDR13.5 |
2.009 |
0.165 |
19.8 |
2.05 |
1.25 |
| 2.00" SDR17 |
2.084 |
0.177 |
21.3 |
2.20 |
1.34 |
| 3.00" SDR17 |
3.072 |
0.385 |
46.3 |
4.79 |
2.92 |
| 4.00" SDR17 |
3.949 |
0.636 |
76.4 |
7.91 |
4.82 |
| 6.00" SDR17 |
5.814 |
1.379 |
165.6 |
17.13 |
10.44 |
| 8.00" SDR17 |
7.570 |
2.338 |
280.7 |
29.04 |
17.70 |
 To purge, flush and fill a large geothermal system with larger diameter pipe and hundreds of thousands of feet of pipe requires a powerful flush cart.
The flush cart shown includes the following features required to flush debris and purge the air from a system with up to 6" (150 mm) diameter pipe:
The cart is built witha 5-hp pump capable of 165 USgpm (10.44 l/s) at over 80' (24 m) of head. The lightweight aluminum tank keeps the cart light and maneuverable on air filled tires with stair tracks. A stainless steel & brass lift out filter basket traps any debris flushed from the system. 2" (50 mm) piping with full port 3-way valves allow you to reverse the flow through the system easily if needed.
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