For Pipebomb usage, he will sustain only a certain amount of damage before he becomes immune, for about 3-5 seconds. in 5 seconds, he can haul *** and pretty much wipe out a good amount of pipes and the team is left will a bigger job to down the Pat. I personally have planted 24 pipebombs on the floor as a demo and he steps/runs on those and takes damage and is still standing. There is a good reason for that.
Pipes - to be effective, need an area to be effective. NEVER weld a door where pipes are, as the pat will fire a rocket and pretty much destroy or make the pipes inert. If there are pipes that wont explode, when the Pat is near them, shoot them with a flare or pistol. AIM for the red light.
Place 4 pipes on each side of a closed door, about a pace two from the door. He will approach the pipes near the door, take damage and either run to heal, or just be ticked off. In that latter case, when he opens the door, that brief delay may be just enough for him to take max damage to the pipes inside the door.
Also, when placing pipes, try to avoid placing them where players are going to peek to see which way he is coming. If a Pat shoots a rocket, those pipes - and the player - are probably going to be gone.
Once the pipes are down, its not over. The common zeds will come in groups and take out those pipes, so its important for the team to protect those pipes, trying to save as many as possible for the Pat. its important to know what combintion of zeds will activate a pipe bomb. You can offset this by placing a single pipe a bit farther out, in the direction you think the Zeds will be coming from.
The Team has to remember that they can buy pipes at the extreme end of cost, or they can throw the demos - no more than 2 in a Team of 6 players - cash to get pipes and scatter them in the area of concentration. No one is going to have the need for cash at the end of the wave, so, give it up. BUT give it up with plenty of time on the clock.
An effective Demo should be able to get 24 pipes down, have armor and one decent weapon to reduce weight. You DONT have to place down all 8 pipes and then run to the trader. I typically place 6 down.... Run to the trader and head off in another direction, place those pipes down. I can place 24 down and have 8 in pocket to replace any area that gets knocked out by a rocket, running Pat or pile of zeds. One more thing - survivability of a demo isn't the greatest, so place those pipes down right after sighting a close Pat.
Stay away from your pipes, because if they explode, the damage/kill radius is quite large.
At the bottom of the page, at the following link is the damage values for pipes vs a Pat(s).
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atriarch_extermination_tactics" target="_blank">
http://kf-wiki.com/wiki/Help:Patriarch_extermination_tactics