The altitude at which a pump is operated will enhance or diminish its performance. At higher altitudes atmospheric pressure is decreased reducing suction lift. For this reason the pump should be located as close to the water source as possible. The table below shows suction lift altering at several locations for 4 different example pumps.
| Altitude |
Pump A |
Pump B |
Pump C |
Pump D |
| Sea level |
10.0 |
15.0 |
20.0 |
25.0 |
| 2,000 feet |
8.8 |
13.2 |
17.6 |
22.0 |
| 4,000 feet |
7.8 |
11.7 |
15.6 |
19.5 |
| 6,000 feet |
6.9 |
10.4 |
13.8 |
17.3 |
| 8,000 feet |
6.2 |
9.3 |
12.4 |
15.5 |
| 10,000 feet |
5.7 |
8.6 |
11.4 |
14.3 |
Altitude affects engine performance as well. A rule of thumb is that gasoline and diesel engines will lose 3% of their power for every 1,000 feet of elevation. This is due to the "thinner air" or lack of oxygen at higher altitudes. The reduced engine speed results in redced flow and head. The table below shows percentage drops in performance as elevation increases.
| Altitude |
Discharge Flow |
Discharge Head |
| Sea level |
100% |
100% |
| 2,000 feet |
97% |
95% |
| 4,000 feet |
95% |
91% |
| 6,000 feet |
93% |
87% |
| 8,000 feet |
91% |
83% |
| 10,000 feet |
88% |
78% |
Many engine manufacturers offer methods of overcoming this loss by offering high altitude cylinder heads, as well as carburetor jets and air cleaners designed for use at higher elevations.
Water temperature and suction lift have an inverse relationship. As water temperature increases the practical suction lift decreases, because warm water contains more entrained air, causing the pump to lose its ability to prime. If the water is too warm, it may be necessary to locate the pump below the water level. This creates a net positive suction head (NPSH). Always be cautious when pumping hot water as it can damage your pump. It is advisable to contact the pum manufacturer to determine the maximum operating range.
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