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Relay Pump Operations: Who Says It's Just for the Long Lay?

Paul Shapiro

The following flow tests were conducted to compare short LDH supply line evolutions supplied from a pressurized hydrant system versus a relay pump operation from the same hydrant to boost the pressure/flow. These tests were conducted with 4” and 5” supply lines, various lengths of supply line up to 500 feet, and weak, average, and strong hydrant systems. Most flows were considered to be at least satisfactory, if not better, for the initial water supply when using hydrant pressure only to move the water.

Flow Test #1

Our first flow test was conducted on what was considered to be a relatively strong hydrant system. 500 feet of 5” LDH SUPPLY HOSE with a maximum operating pressure of 185 psi was used in the evolution stretching from the hydrant to the fireground. The first part of the test used hydrant pressure only to move the water to the receiving engine.

A flow of 1050 GPM was achieved. This is a great start for a large flow water delivery operation, but not enough. Next we placed a second engine at the hydrant to relay pump to the receiving pumper. We more than doubled our flow achieving 2225 GPM. This test is a good example of maximizing a single hydrant and pumper.

Plano, TX engine companies moving 2225 GPM in a 500’ relay