The Sewer

"This is not going to be sanitary..."

- Louis "Hospital's on the other side of the waterworks."

- Bill

The Sewer is the third chapter of the first campaign, No Mercy.

The Survivors begin in a safe room at the Pawn Shop. The usual Tier 1 weapons, first-aid kits, an extra pistol, and an ammo stash are provided.

This chapter has the Survivors fighting an infected horde before entering a warehouse and the Fairfield sewer system to exit via a manhole in front of Mercy Hospital.

Campaign
When starting from this chapter, all four Survivors will grab a Submachine Gun.

When Tier 2 weapons are found:
 * Bill will grab an Assault rifle
 * Francis will grab an Auto shotgun
 * Louis will grab an Assault rifle
 * Zoey will grab a Hunting rifle

Otherwise, they will keep the weapons they had from the last chapter. (See The Subway for a list of weapons they will grab there).

If you're starting on this chapter, make sure everybody grabs a first aid kit and a weapon. They are entirely necessary to everyone's survival. If you started in an earlier chapter, heal up if you need to and take what you can. As there are lots of open areas on this level, the submachine gun is a good option, though with luck, Tier 2 weapons will become available shortly.

The first area of this map is relatively small. After opening the safe-house door you can turn either left or right. Going left brings you straight to the back door of  a Burger Tank restaurant. Turning right takes a longer route to the Burger Tank but gives you a chance to explore a two-vehicle garage, a parked truck and various alcoves for Pain Pills and Grenades. Regardless of the route taken, Smokers and  Boomers  are a real threat. If you move slowly the AI Director will send a Horde at you.

Proceed through the Burger Tank, mopping up loitering infected as you go. The diner front windows allow you to snipe all visible enemies within a large courtyard area. Take your time, this is one of the few spaces where you will not be hit by a hurry-up horde. Pay attention to rooftops and dark corners for Smokers and Hunters and practice stealth and evasion if a Witch is present. Be careful not to shoot the gas station pumps because this will cause the facility to explode prematurely, and you should keep this destructive opportunity in reserve for the battle which lies ahead..


 *  This is one of the four most likely times for a Tank to appear (especially in versus mode). If you hear one coming, be sure to stay in the open area right outside the diner. This offers the most maneuvering room, so the Survivors can employ anti-Tank strategies. 



Note that prior to blowing the gas station, it is possible to access a series of rooms overlooking the scene containing supplies and Tier 2 weapons by jumping up on a stack of cable drums (look for the blue dumpster that provides a directional marker). Alternatively these rooms can be reached after the gas station has been destroyed by using the resultant rubble pile. With the release of The Sacrifice, melee weapons can be used in the No Mercy campaign in Left 4 Dead 2. Because of this, players with melee weapons must take care when near the gas station since a misdirected melee swing can make the gas station explode on top of them.

To the left of the gas station is a scissor lift. A Survivor will instruct you to get on the lift. Activating this device triggers this campaign's second Crescendo Event. A sizeable horde lasting some minutes will attack from various directions as the lift moves noisily upwards to the rooftop of a nearby warehouse. Provided the team is quick to take down any Smoker, it is possible to defeat the attack by holding out on top of the lift. Alternatively the team can form a defensive huddle in the corner of the roof next to the lift.

Ranged weapons are particularly effective because the infected will seen at a distance and approach from a limited number of predictable directions.

If you are pulled from the raised lift or need to ascend or descend it for any reason, it comes equipped with a ladder on the gas station side.

When the moment is right, firing at the gas station will instantly kill any nearby Infected and start a blaze to destroy any others who attempt to attack from that direction.

Once on the rooftop, proceed along to the large-windowed room. If you are still fighting the horde when you get here, don't jump into the hole. Throw a Molotov down into the hole to burn any incoming Infected and shoot any that try to come in through the window. Once the horde has been dealt with, you can drop down the hole into another room with a first-aid cabinet, an ammo supply, and sometimes Tier 2 weapons. When ready to proceed, either head down the stairs to the warehouse floor or into a room down the hall which has a view of the warehouse (and sometimes a Pipe bomb).

''Note: Under the overhanging roof of the warehouse, in the back left corner, there is a metal door. This door can normally be opened by a button on the inside of the building, or by a Tank crashing through it. If the Tank breaks the door open before you start the Crescendo Event, feel free to punish him for his mistake. Before a recent patch, it was possible to break the door using melee attacks, effectively allowing you to bypass the Crescendo Event. Hit the door roughly in the center until you hear the same sound that is played when you successfully melee shove an Infected. After hitting it for a while, it does break. Alternatively, if one has a spare pipe bomb at this point, or even a propane tank, they can throw it near the door (and shoot it, in the case of the propane tank) and severely weaken the door, if not completely break it. ''

Be sure to heal up if need be before entering the warehouse, as this is a notorious ambush spot. Proceed quickly, and stay close together. Smokers frequently hide on the catwalks, while Hunters and Boomers will dwell among the dark aisles. Don't give them a chance to stop your advance. If they are encountered, punch a Smoker's victim to release them from its hold, and destroy Hunters as quickly as possible. In the event of Boomer vomit, quickly move to a nearby wall, and move as soon as you can see again.


 *  This also happens to be the second of the four likely spots for a Tank to appear. If he appears, don't wander too far from the first part of the room, since the Smokers, Hunters, and Boomers are just itching to add to the chaos. Instead, prepare for this battle by hitting the button to open the door before entering. If a Tank appears, retreat back outside, where it may be more easily disposed of. 

Once out of the warehouse, move down the alley and follow the hallway until you get to a stairwell. At the bottom lies a generator room, with a manhole at the other end. Since the generators provide lots of cover for Special Infected, make sure to check behind these as you go. You have two options to get to the sewers.


 * 1) Get to the manhole on the other side of the room, and drop down onto a wooden plank above the sewers.
 * 2) In the middle of the right wall, there is an often-overlooked room. This room contains another manhole into the sewers, and sometimes a Pipe bomb or a Molotov. However, Special Infected are able to crawl out of this particular manhole, so watch for that.


 *  The generator room is the third location a Tank will often appear. If you have not encountered one yet, you will here. Either immediately leave the confined spaces of the stairwell, or retreat back the way you came while shooting. Molotovs are dangerous in the limited spaces this area contains. 

If you dropped onto the plank, there will be a "T" intersection. Take the right-hand turn, and then make a left. If you took the other route, proceed forward to an intersection, and then continue forward. This will place both groups traveling along the same path.

While the sewers themselves are rather wide-open, there are many small passages off of them. Special Infected love ambushing unsuspecting Survivors out of them. Avoid this by keeping your distance from them, and staying close together. The path to take is lit up by overhead lights, so stay out of the dark areas to proceed. Eventually, an open door will appear along one of the walls. Pass through it into the room beyond (closing the door behind you as always). There will usually be an ammo supply on the ground, and there is a chance that grenades, pain pills, Tier 2 weapons, or even a health pack will be here. Enter the nearby tunnel to proceed.

After the tunnel turns right, move forward until it opens back up into the sewers. There is an offshoot to the left where Special Infected will hide, so be wary of that when you pass it. Once out of the tunnel, follow the same lighting rule to get to a ladder. This ladder will take you out of the sewers. Before progressing, now is a good time to heal, pop some Pills and check ammo.

A surefire way of getting safely out of the sewer is to have one player switch off their flashlight and use a pipe bomb. This person takes point and climbs the ladder followed rapidly by the rest of the team. The moment the point player reaches the surface, the Pipe Bomb is hurled in the direction of the hospital (the way the ladder is facing) and that person backpedals to put their back against the wall of the building nearby, covering the rest of the team as they leave the sewer and link up again. From there it is a simple fire and movement drill to reach the hospital entrance. Note that Special Infected love this area and a Witch will often spawn somewhere inconvenient. Alternatively if someone has a Molotov, they should carefully throw it so that it lands just outside the sewer exit, burning any would-be ambushers. Failing that, make sure the team leaves in shifts of two so there will be someone to help out. Backing up to the aforementioned building wall will channel enemies and greatly improve the Survivor's odds.


 *  This stretch of the sewer is the last of the common areas a Tank will spawn. Move to an intersection where there is slightly more room to move. If in the second area, do not face him on the street. Cars litter the road, and are a surefire way of someone getting incapacitated or killed. He will follow you into the sewers, so take him there rather than put everyone at risk up above. 

Everyone out? Good! The hospital is in sight. While it may be tempting to bolt straight to the safe-room, many teams have died by doing that. Smokers will dwell above the entrance, while Hunters and Boomers will attempt one last attack inside. Use the ambulance just outside the doors as a waypoint, and quickly check inside it. A healing item will often spawn in here, which will be valuable when you proceed. If you are playing in Versus, the item won't be valuable, but a Special Infected may choose to hide in there. Either way, move at a swift but regulated pace using fire and movement to enter the hospital, and jump the counter to enter the safe room. If time permits, a consulting room to the left may give up a supply item like a Pipe Bomb.

Left 4 Dead 2 Version
The map is unchanged apart from weapon and enemy profiles.

Survivors
Remember all those devious places the Special Infected like to lurk? Human-controlled Infected will ruthlessly use these to slaughter your entire team. The best way to counter them is to deny them a good chance to do so. Gear up quickly, as well as the second pistol which now presents itself, and rush to that diner. The less time you spend here, the better.

If you're feeling lucky, go through the doorway to your right. This will lead you through a storage area, and on the other side is a small garage area. This area may hold Tier 2 weapons, and it's possible that other useful items (such as pills and various grenades) will spawn in the storage area. If you do do this, move fast. The longer you're out here, the longer the Infected have to mess with you. As long as everyone moves with a buddy, everything should be fine. Once you've gotten your fill, run down the alley, turn left, and go inside of the restaurant.

Stick together! Yes, yes, you already know, but don't even split up into two groups of two. The large amount of hiding areas makes this a dangerous level to get separated in.

Always search the room above the blue dumpster and the garage at the beginning. You don't have the advantage of keeping Tier 2 weapons from the last section.

Be especially careful of shooting when you see a Special Infected and hear a Witch; they like to conceal the Witch from your initial line of sight, and you probably know very well what happens when you shoot at her.

Once you're in the room with the hole—assuming you took that route—hurry up and drop down. If a Smoker drags somebody out from the window, it's almost certainly a kill. After entering the room below, which has ammo and a First-Aid Station, be sure to stay away from the windows. They can still pull you out, and needless to say, that's not much fun, either.

Have the last person run backwards down the dark hallway after the warehouse. This way, he can protect himself from any Infected planning a flanking maneuver.

Always enter the room on the right wall of the generator room. It is much easier to protect against lurking Special Infected in there. Once you've entered the Sewers, be especially wary of the tunnels. They're a great place for Infected to hide in, and getting ambushed due to one's carelessness when running by the tunnels isn't very nice. Make your way to the last manhole of the sewers. When there, try your hardest not to let anyone go up alone; this is a crucial choking point for the Infected, and they can pull you away or pin you down one by one as you get off the ladder. Get everyone up, one way or another, and make a run for the hospital.

The Infected
Techniques:
 * Pre-Diner ambush ― The Smoker waits on the rooftops, the Boomer in the alley to the left of the diner, and the Hunters in the alley to the right. As soon as they come in sight, the Boomer vomits over as many as possible. Immediately afterwards, the Smoker and the Hunters grab three of the Survivors, being sure to get any not covered with bile. If done right, this can be a game-changing maneuver, or even outright kill the entire team with some luck.


 * Three-Survivor pin ― Obviously, it is possible for three Survivors to be incapacitated at once by using the Smoker and two Hunters. Because the Tank frequently spawns early in the level, it is possible for him to concentrate on one Survivor enough to kill it, though it is risky. To help with this, the Boomer should also target this Survivor, vomiting and then clawing it. Once they are down a member, set up an ambush somewhere dark, such as the warehouse, and grab all three of them. They won't be able to retaliate if done quickly.


 * Witch Ambush ― Though this is a very recognized technique, the Sewer is arguably the best stage for this trick if a Witch spawns in the depths of the sewer. The dark lighting allows a Special Infected to block out the Witches glowing red outline by crouching in front of her. The darkness can also block out the Special Infected themselves, especially if they are a Hunter. When a Survivor sees you, they'll shoot you, and alert the Witch. When another Survivor comes to help the incapacitated, you can pounce or rope them. A Boomer will have already exploded, and hopefully splashed onto the Survivor, pretty much dooming them, and earning you points. When performing this trick, it's good to have another special Infected, preferably a Smoker, to grab a third Survivor.

The Boomer: There is plenty of opportunity to wreak havoc among this level. Try dropping off a roof into the middle of the Survivors for a surprise, or vomit down upon them, letting gravity extend your reach. Hide in areas they will have to pass through to make the arrival of a horde inevitable. Stay out of any open areas where you will be vulnerable, and spawn in an area in front of the Hunters. Whenever a Tank is attacking, take advantage of the situation and catch as many Survivors as possible in your bile.

The Hunter: This map is more difficult for you than for the other Special Infected. Team up with another Hunter to maximize your effectiveness. Climb to a high place before pouncing in order to increase the bonus damage you do, such as the roof opposite the diner. When the Survivors activate the lift, wait at the top, and then pounce on one. Because the Hunter pushes back his victim, you are likely to knock the Survivor off the lift, giving you a bit more time while his buddies figure out where he went. When the Tank appears, jump on healthy Survivors he is going after. Even if you die, you allow the Tank to catch up and tear that Survivor apart. The one way drops into the sewers are another perfect place to pick of a straggler for good, with the others unable to climb back up you can almost certainly kill that Survivor. Another good tactic is to wait at the top of the red ladder exiting the sewers and pounce the first one up, sending them crashing back down the hole to the base, delaying the team enough for a Boomer to wreak havoc with a vomit attack.

The Smoker: This area is made for you. At the beginning, climb to the top of the rooftops as quickly as possible. If you climb above the safe-house, you have a good line of sight to yank a Survivor out of the diner. If possible, always try to be behind the Survivors, since pulling someone backwards in the level is more effective than pulling someone forwards. Pulling a Survivor back down the hall after the warehouse is a particularly good example. If you can manage it, try to strangle a Survivor who just went down the manhole. At the hospital, either grab the last Survivor to climb the ladder, pulling them back down into the sewers, or the last one into the hospital. When the Tank is around, be sure to target healthy Survivors the Tank is not currently chasing. Also, you can get onto the fire escape near the climbable building by the safe room; people do not expect you to be up there. If the Survivors don't shoot the gas station at once, another risky strategy would be to hide behind one of the gas pumps in the gas station. Once the Survivor move close enough, grab one of them. If they shoot you, there's a chance they'll shoot the gas pump and kill you in the explosion, along with your victim. If you're lucky, this could even result to death of all the Survivors if they are close enough.

The Tank: First off, be sure not to break down the metal door, or you will allow the Survivors to skip the Crescendo Event. When playing as the Tank, be careful to avoid fire, this will cause your health to go down significantly until you die. Go after the weak Survivors first, pummeling them until they can't get up. Since the Survivors are likely to be faster than you, you need a way to catch them. If you ignore the first downed Survivor for a few seconds, somebody will inevitably try to get them up, during which time they can't move. Use that time to run up and put them in the first chum's shoes. There are forklifts and freight dollies near the Crescendo Event, as well as a car and dumpsters in the alley you can punch into the Survivors to incapacitate them. Even after such, you are still quite the threat. When the Survivors open the manhole cover to get out of the Sewers, be sure to have something to shove down there. If done right, it will incapacitate all survivors on the ladder and extremely hinder their progress. One such example of an effective use of this tactic can be seen in one of the YouTuber Criken2's "Funny Moments of Getting Owned", in which a dumpster was shoved down the manhole and seriously hindered all progress, blocking the ladder. Keep in mind, however, that punched objects such as dumpsters and cars will vanish after a minute, regardless of whether they receive multiple punches or not.

Survival
Lift Method


 * Have the team ascend the lift, activate it to bring it up level with the sloping roof and engage the horde on an ad hoc basis. Since the attackers have to traverse a wide area of open ground and they follow two main lines of attack (climbing the ladder on the lift and onto the sloping roof via the trucks in the yard below), they are relatively easy to defeat (in fact, their behavior is sometimes quite puzzling because those charging towards the team across the sloping roof may often jump to their deaths just before they attain a threat range). Note that horde members not only spawn in the yard below, but also from the roof to the right of the lift, so a weather eye needs to be kept on this part of the stage. Have one player cover the head of the ladder on the lift, a shotgunner looks to the sloping roof and two with rifles ply their fire opportunistically. The only risk with this position concerns Smokers, who can pop up on the roof to the right, but fortunately they only drag players a short distance and the angle on the shot from the top of the lift makes it easy to take these unimaginative creatures out. A good idea is to wait until a section of the horde is in the right place in the yard below and then have one player fire at the gas station, thus blowing it up and wreaking thereon great havoc and execution. The benefits of elevation and lack of obstructions make it easy to bring down most Boomers and Tanks at comfortable ranges. Do not make the mistake of holding this position at all costs in the face of a Tank assault; instead, exercise good tactical judgement and reposition the team out on the sloping roof as needs dictate.

Rooftop Corner Method


 * Once the lift has risen, you will have a sloping rooftop to your right featuring a right-angled corner where this roof meets the warehouse wall. This corner is an effective position from which to fend off the Infected. Two people cover the lift and gun down attackers who have climbed its steps, whilst the others cover the sloping rooftop. The Common Infected will mostly charge in thin lines making them relatively easy to defeat. This method deals with Boomers, Smokers, Hunters and Tanks effectively since they find it difficult to get to players clustered under the roof overhang. Keep in mind that this method will only work effectively if all of the Survivors keep themselves bunched together in the corner.


 * Provided the Survivors keep themselves in the corner, the Boomer will spawn on the rooftop of the building facing the corner and can be handled with little difficulty since he normally self-eliminates by jumping down, hitting the ground and exploding. However, if one or more Survivors leave the corner, the Boomer may either spawn on the ground below and ascend the ladder (making him an easy target), or spawn on the rooftop above and drop down onto the sloping roof. In any event, expect at least one Survivor to be at risk of receiving a face full of bile.


 * Hunters are forced to ascend the ladder, as they believe that there is no other good location from whence to mount a pounce. This gives the Survivors ample time to kill him as not only does it take a few seconds for them to come off the ladder at the top, but they hesitate to pounce once they are up on the lift platform. Hunters rarely attack from across the rooftop, and even if they do, players have time enough to spot them and engage them before they can get into pouncing range.


 * Provided players are close enough to the corner, there is no risk of Smokers dragging anyone off the sloping roof down into the courtyard below. Instead they will appear on the roof above and drag people against its supporting wall. At most, individuals will taken only a few meters away from their team mates so they can be easily freed and the rooftop Smoker eliminated. Like Hunters, Smokers may also attempt to climb the ladder to get to the Survivors but this is rare.


 * With the benefits of elevation and lack of obstructions, players can spot and engage the Tank from long range and with plenty of time to bring him to submission. The Tank will generally climb on top of a truck and then mount the sloping roof so that he can make a final run across the roof towards the Survivors. However, he may occasionally avoid the truck and climb the lift's ladder, in which event the team will have to fall back along the sloping roof in order to open the range and keep themselves out of immediate danger.

Second Floor Method


 * The first room on the second floor that you enter via the windows on the rooftop is a fairly easy position to defend. This is a popular and effective place to defend mostly because in this room, there are a total of five Pipe bombs and three Molotovs. From the back of the room, there is a corridor-like passage. Facing away from Mercy Hospital, two Survivors can shoot down this passage and restrict movement of the oncoming hordes. The other two can face towards the other direction that the Infected can attack from and defend there. If things get too much to handle at the front, one of the Survivors guarding the second passage can move over to help defend the first one.


 * This tactic deals well with Smokers, as it is too close for them to be effective. It also deals well with Hunters, as they are heard long before they are seen and infrequently, they don't even reach your position. The downside to this tactic is the Boomer. However, as long as the team stays fairly far back and shoots him before he can do anything, they shouldn't have a problem. The Tank is dealt with by either fighting him whilst maneuvering around and around the passages, or by using one of the three Molotovs to set him alight and then avoid him until he dies.

Behind the Scenes
In earlier footage, it seems that the players had to get to the roof by going through the building to the left of the gas station, not by using a lift.

An early picture of the front of the Hospital shows that there was to an advertising billboard to the left of the hospital at one time.