🔥🔥 Wye Operations 🔥🔥
Departments all over the US routinely use wye operations to establish more than one attack line off of one supply.
Wye ops make it easier to get that second attack line in place when you’re outside of the range of your pre connects, or when you’re far away from the truck.
But Wye Operations have downsides.
- Wye Ops commit both attack lines from the same starting point down range.
Often, it would be better to pull another attack line to a different location (Line 1 front side of house, Line 2 back side), but once we get out of range of preconnects, Wye Operations allow us to be lazy. Why should I stretch another 400’ of hose when I can just drop 100’ on the wye that’s already down there?
Although convenient, this can set us up for failure by not providing the mobility that we need with that second line.
- You CANNOT pump two attack lines from a wye appropriately.
When you pump attack lines through a gated wye, you are sacrificing accuracy for convenience.
If I have two attack lines on a wye, I have to pump the supply line for both of them. If one attack line is different (longer, different nozzle, different size hose) then the one that has a lower PDP requirement is going to be mismanaged.
Take this example:
- 200’ 2.5” supply to wye
- 100’ 1.75” attack line 1 with 150@75 fog nozzle
- 100’ 1.75” attack line 2 with 7/8” smoothbore
Total PDP = 153
Total Flow = 328 GPM.
Attack 1 is our PDP driver. This is the line that we have to pump for, because it has a higher pressure requirement. The attack line itself requires about 110psi.
We cannot pump this appropriately for attack 2!
Attack 2 is the lower requirement line. So what happens? Attack 2 gets over-pumped.
Attack 2 inherently gets over-pumped, and ends up getting a supplied nozzle pressure of 61 PSI. This sucks for attack 2 THE WHOLE TIME because with increased NP and GPM, comes increased nozzle reaction.
- When one attack line shuts down, the other gets hammered by the PDP that is being pumped for both.
In the above example, we are pumping our supply line at 153 psi to supply both attack lines. If attack 1 closes the nozzle, attack 2 now gets EVEN MORE pressure.
This would happen even if the attack lines were matching.
If attack 1 closes:
Attack 2 goes from a nozzle pressure of 61, to a nozzle pressure of 76! Attack 2 flow raises to 198 GPM! Nozzle Reaction increases from 73lb to 92lb. THIS SUCKS.
So now what happens? Attack 2 shuts down due to unmanageable nozzle reaction.
This is how you create an ineffective fireground through hydraulics!
- Supply line failure = emergency for 2 different attack lines!
If the single supply line bursts/burns through, you now have a pressure loss emergency for BOTH attack lines!
Best practice on the fireground is 2 complete separate attack lines. Even if that means we have to stretch more hose.
Sure, some places routinely use wye operations effectively. But just because they do it, doesn't mean that the downsides are invalid. This simply means that they have accepted the risks in favor of the benefits:
- Quicker deployment of two nozzles
- Less hose to stretch
Every decision we make on the fireground should weigh the risks versus the benefits. Including which lines we deploy, and how.