I’m sure most of you have heard the term “maximizing a hydrant” which involves attaching lines to every port of a hydrant to get every ounce of available water into your pump. But exactly how much more does that give us than a 4½" port alone? I’d always wondered how much more, so I decided to perform a test using a flow test kit. Keep in mind that these results will not reflect the performance of all hydrants, but it is good info just the same.
The hydrant used was a private hydrant in the parking lot of vacant commercial property; its static pressure was 65 psi and it's on an 8" water main.
The pump used was a Hale QMax rated at 1,000 GPM with a 2.1 ratio, and it was driven by a Detroit 60 series.
First, we stretched 100’ of 4” hose off our 4” discharge and connected it to a ground monitor. Then we attached a 2½” smooth bore pitot tip used for service testing. We then made the following hydrant connections:
A. 4½” steamer to Piston Intake using 50’ of 4” hose
B. 2½” port to auxiliary intake using to 50’ of 2½” hose
C. 2½” port to 4” Storz adapter to front intake using to 50’ of 4” hose
Then we tested how many GPM we could get from each combination of intake arrangements, opening each as needed, and drawing the residual intake pressure to 10 psi each time.
A - 1,306 GPM
A & B - 1,481 GPM - 13% more than 4½" port alone
A & C - 1,751 GPM - 34% more than 4½" port alone
A, B, & C - 1,784 GPM - 37% more than 4½" port alone
The big point here is that using LDH hose
on the 2½” port, feeding a large intake
yielded more than twice
the amount of additional water than using a 2½” hose to a small intake. I think this is evidence that we need two large valved intakes on every Engine/Quint to receive large volumes of water, and two LDH discharges to move this water to another location. And I do mean true LDH discharges, not 2½'s with LDH adapters screwed on.